incompatibility significance in crop improvement

Incompatibility in Angiosperms: Significance in Crop Improvement

D. C. SASTRI ICRISAT Cmm, Prz&mrhem, A&ra -11. Irdin

I. I n l a d u c t i o n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 . . . . . I f . fn~omptibi l l ty

A scrr.incomp.tibi~it~ (intr"&tili;j ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' 72

. . 73 B Inlcnpecific in-patibility . . . . ' 1.1 : . : : : : : : . . . . . 76

111 C ,rc"mv~n , i~n d h e n . . . . . . . . . . . . . . . . . . . . . . . 77 A . T h e ur1y mnbad. . . . . . . . . . . . . B Bud poum.,ion . . . . . . . . . . . . . . C . Application of plvll growth m.ul.ron . D Tcrnperarum snd incomp.ribility. . . . E . Recognition pollen and incomprhbtliry . F. 1mmuno.upprruults u ld inromp.tibility C Miu.ell.nco". method. . . . . . . . . . . H Generic u ld cpdopicll m i p u l a t i o n . 1. Thc u .rim methods. . . . . . . . . . .

C a n ~ l u d i n ~ re-*. . . . . . . . . . . . . . xercrcn- . . . . . . . . . . . . . . . . . .

I . INTRODUCTION

There is a continuous need for modifying -p plants lo suit chang- ing human nccds in existing cnvimnrnent~ m d to tit the crops into new environments. Most often such moditicarions are achieved by by- bridizarion. The objective for rnoditicarbn, such u alleration of a characrtr or intmduaion of a new character into a cultivar, dictates the choice of parents in m y breeding propram. Most often thc parents are d o e to each other taxonomically m d usurlly belong to the same species. However, there are instmcn when the parents are only distantly a n t e d m d may &o be repmductivcly imlared. Such situations are flowing in number. for desired characters are not (and need not be) always available in clorly d a t e d r u a . In nuch c u e s the choice of -nu may be limited m d i s governed primarily by Ihc availability of char.ctcr(s) in a -on; but the uxon in which the character is avlil-

72 D. C. WLI

able may be distantly related, and the hybrid may not be produced at d l , and even if pmduccd it may not be viable or fcnile.

In this article an account of the problems uaually -ncountered in such situations and the methods to circumvent them w discussed. Incompatibility in angiosperms h been known lor about 200 yean. The very uiatencc of t h e r barriers between t u a h u been used as a criterion for taxonomic delimitations, but h u been the cause of frus- tration to plant breeden innrested in transfer of chrncter(s) from one t u o n to another, as well to cvoiutiorury biologists interested in the phylogeny of a group of =-a. The d u t i o n to thin problem has often come from geneticists, physiologirts, and eyrola8ists who have repeatedly attacked thir problem. Commendable p m p u h been made, as in evident by two full-length dieusions on the aubject by the Royal Society, London-"lncomprtibiliry in Angiorperm~" in 1975 and "Manipulations of Genetic Systems in Plants" (Rccs #.I., 1981)-in addition to 1300-page monograph by Profeuor de Netuncoun (1977) and n large number of research and review p a p n on the topic.

11. INCOMPATIBILITY

Incompatibility is defined u the inability ofthc functional mde and female gametes to f u ~ with tach other to form a viable zygote and a hybrid (Arasu. 1968). Incompatibility is u u d here to refer to failure of aced set after either self- or cross-pollinations. Tempord and/or geo- graphic uparation (or iwlation) of two uxa to k hybridized wme- times occur, but incompatibility &odd not be assumed in the* cases. Such problems have been wlved by low.temperature storage of pollen until required or by trrnaponing pollen to overcome geographical sep- uation There we inrtMces when ccruin genetic changer may lead to incompatibility between two c u u . Incompatibility between m a , re. femd to u intenpecific incompatibility (or crou-incomprcibility) in the literature, p m e n u promircuous hybridiation. whertu incam- patibility within a taxon, referred to u intraspccific (or elf-) incompatibility, ia an evolutionuy atratcgy to promote outcrossing.

For convenience, rberefore, incompatibility u n k d k u u e d under two broad titles: intrupuific and internpccirrc. In the context of crop improvement, however, incompatibility between uxa is of c a t e r concern u it pmcnts the desired transfer oipeaes. But investigations on several upecu of ulf-incompatibility, and wmc on int-fic incompatibility, have m d e d Ib.1 inhibition of pollen gemination and paUen be pawh w a i m i l u in both. T h e n may d w k a common genetic wntml; Tor iruuncc, in Nicdma, Purdcy (1976) obvrvcd that

ANCIOVUM INCOMPATIBtLITY AND CLOP IMPROVEMENT 73

alleles governing self-incompatibility are effective in interspecific in. compatibility Jso.

About half or the flowering plant species invcatigated so far have been found to be aelf-inmmpatiblc (de Nettancoun. 1977). Self-incorn. patibility is the rejection by a plant of its own pollen, or pollen from ;he MUTIC genotype, bebre'or ifter it has germinated on ihe stigma, but mostly before fertilization. It is believed to be the result of an in. teraction between the male gametophyte (pollen grain) and the sporophytic tissue of the pistil. Geneticists have recognized taxa with either a sporophytic or a gamcrophytic type ofsclr-incompatibility depending on whether self-incompibility is controlled by the genotype of the sporophyte (pollen parent) or that of the gametophytc (pollen grain), respcctively. Brewbaker (1957, 1967) found that in t u a with the spor. ophytic type of ~1f-incom~atibilir~,'the pollen grain is usually three celled at anthesis and is inhibited on the stigma, whereas in t u a with gametophytic self-incompatibility. pollen grains are two celled at anthesis and it is the pollen tubes that arc inhibited in the style. This Kems to be the general trend, but there are a few exceptions (Brcw- baker. 1967).

During h e last two decades there has been a great interest in structural and functional aspects of the incompatibility reaction. In spite of concerted efforts by ph~siologists and biGhemiatd, a precise interactive model is rtill to be defined.

~~m~&brompr~!nr . ~;msr<a 0 - h t a , RopLnw rotrcw, fnuo rotroo I h r omfa LBrassicaceae). Cormor bibinnaw. Hrl~onthw annuw (Asreraccae). and ~ ~ o r n w a app. (~onvolvda~eae) are well-known exampler of the s ~ o r o ~ h v t i c syrtcm of =If-incom~atibdity, and in these cases incom- btibie b ~ e n is invariably inhigitcd on.the stigma. A phenomenon correlated with &is id the characteristic synthesir and accumulation of ullore in the form of lenticular deposit: in thc stigma cells in dircrt contact with the pollen grain (Dickinwn and Lewis. 1973; Heslop. Huriaon and Hedop-Harriwn, 1975). and this has been suggested as a bioassay. This phenomenon is strongly ruggmive ofthe f u t that the p o k n and the pistil do communicate wirh each other. Cytochemieal mvcuiguions have mve.led rh.t there uc certain ~ m t c i n ~ e o u s sub- --on the surface of the polien W n s (Hntop-~;riron nd., 1973, 197k Dickinson .ad Lewis, 1973: Howlnt n d.. 1975) M well u on ni&a cells (Mutuon d A , 1974; ~ n l o p - ~ a r r i k n d 2.. 1975; Knox

n d., 1976; Heslop-Hurimn and Shivmna, 1977; Healop-Hamson, 1981). The pollen wall pmteins are labile and diffuse within minutes on the moist substratum~of the stigma or on agar gel (Herlop-Harrison a a l , 1974). The= diffuuuter from incompatible pollen am potentially caoable of inducinn ullose svnthcsis in the atinm; oaoillae iDickinson a h Lewis, 1973; kcalop-Hirrison n .I., 1973, 167i). 0n'athe other hand, incubation of the stinma in a orotein-dinestinn enzvrne (Hrsloo- Harrison and Herlop-Harr:son, 197i; ~edop-kar r r son Ad Shivank, 1977) or coating the nimna with concanavdin (a lectin) (Hcdoo-Har- =ison, 1976; ~ c o x n d: 1976) has been found ;o dirtu;b'thc Ghsvior of even compatible pollen grains, i.c., preventing the entry of pollen tubes into the stigmatic tissue. Serological and electrophomtic inver- tiaations on E. o h a r m atimna proteins have led to the identification of th; self-incompatibility .]!ele (S allele) specific proteins (Nasrallah and Wallace. 1967; Nasrsllah rr d., 1970; Sedgley. 1974; Nishio and Hin- ata. 1977, 1978, 1980). The mosr likely source of these proteins is the r r i m a surface. u shown for Braria (Healo~-Harrison el al.. 1975). Fu%hcrmom, it har also been r e p o n d [ha; Emsir . rtigmr; have h factor that inhibits =If-incompatible pollen in uiiro (Ferrari and Wal- lace. 1975. 1976). '

The nature of the d e n main in contact with the stimna oaoillae - . . dctcrmines the direct& of ;he events leading to either pollen acccp- tance or niection. The Tuat event, vir.. adhesion of ulf.incomoariblc pollen, is rfower than that of the compatible pollen grains in 8 . ; k e a (Roggen, 1975; Stead .I d., 1979; Roberts tl al., 1980). This ir followed by the diffusion of the pollen wnll proteins onto the stigma accompanied by imbibition by the pollen grains of moisture from stigma. Stead n a/. (1979, 1980) and Roberts rr d. (1980) have p r 0 p 0 ~ d that hydration of compatible pollen is different from that of incomparible pollen. They haw .]so suggested that them is a protein fraction re- sponsible for pollen main adhesion, m d Fcrrui d al. (1981.) have shown that a hydrop~ilic stigmatic factor is involved in pollen hydration. The next di~cernible c h a e is the ncrmination of the oollen main and the growth of the pollen t;bca, which are different in'comp;tible and incompa$ble poUinations (m reviews by Heslop-Harrison. 1975a,b, 1978a.b).

2. Canulophylu ~r/-ilc~mpoh1ili~ In tax. with gametophytic self-incompatibility. the p n o t y p of the

,potlen (gamctophyte) b rwpondble for the incompatibity (see de Netunwun, 1977). The first observation of chis kind of incompatibility w u in Nkoriora (Eut and MangeldorZ. 1925). Subuqumtly, other t u r , ruck u Pen& d i d o , M u m byt@mm, Trifsliwp pruew,

and U n o f h n o om&, have dso been found to have nameto~hvtic elf-incompatibiity. 1n.thesc t u a the site of inhibition & usuaily ;he avle. and the n i m a is usudlv ewered with a co~ious exudate at the tike'when po1lin;tion norrndiy takes place; thcr;are thus referred to as wet-type stigmas. Lipids, sugars, phenols, proteins, and water have been identified in the stigmatic exudf e of wmc t u a , and a role has been proposed for each of these components in stigma receptivity and pollen germination. In comparing the vlf.incompatible t u a having dry-type stigmas, proteins in the stigmatic exudate of the t u a with wet nigmas have not been attributed with specific roles in pollen recognition and pollen aerrnination. But rotei ins on the s t ima surface have been identked; &ese are extraccli;lar and are prerrk on the stigma papillae during early stages of development. The fact that the inhibition of incompatible pollen tuber in the= t u a it in h e style led East (19341 to suaaest that the inhibition is in wmc way analoaous to the &tig&-ant&Jy reaction found in animals. T ~ I S a s s ~ ~ ~ r i o n has prompted several investigators to propose hypotheso on incompatibility uurming that proteins are indeed the interacting molcculc~ involved in reicction or acceptance of the pollen tubes (see discussion in F e m r i a n d - ~ d a c e , 1977; de ~ettancburt , 1977; ~ e s l o p - ~ a r r i s o n , 1978a.b; Ferrari rr d., 1981b). Whatever the mechanism, it has been amply darificd that pollination triggers a reaction characteristic of the nature of the pollination. This is evident from structural, ultraatruc- turd, physioldgiol, and biochemical comparisons of the compatibly and incompatibly pollinated pistils.

In P. h?&ih no'npparent distinctions have been found between the behavior of the compatible and incompatible pollen grains on the stigma, or even of th; pollen tubes within it. The diITe&nces are ap- parent only when the pollen tubes have come in contact with the atylar tissue ( S ~ t r i and Shivanna. 1980a; Shivanna and Sutri, 1981; Hcr- rem and Dickinron. 1980b). In incompatible pollinations them may be a reduction in the number ofpollen tubes deeper in the styles, slower n t e t of arowth of incompatible pollen tubes and heavy c d o ~ deposits dong rh; pollen tube kngths , ~d abnomulitics at the tube tip;such u welling. burning, or branching of rhe pollen tubes. Incompatible pollen tub; w d a aremuch thicker <ban thou ofcompatible pollen tubes (vander Pluijm and Linskens. 1966). Diflerencer have been found in the pistil dm. h P. Cbn&, for instmce, Her- and Dtckinson (1979) obvrved that in a compatibly pollinated pinil, starch and lipid reserves are &*red in &c ayk ruler than d t u incompatible pollination. In the inoanpuibly pdtinucd pistil of L-ka #nu&wm, it w u found rh rlt-&*tibk poUcn tube &-me& a concentric organi- uriw of tbc mu& d p l v m i c re t idurn (de Nmurcoun rr d.,

1973a.b. 1974; Cresti ad., 1980). which is inhibitory for protein syn. thesir. A similar observation was alw made in P. hybnik (Cresti rt el. , 10701 --.-,.

van der Donk (1974a.b, 1975) reported differences in protein and RNA nynthesis in compatibly and incompatibly pollinated piitils. In N i l i a n n a&& there ue differences in peroxidase patterns correspond. ing to the kind of pollination (Bredemeijer, 1974). Around 18 hr after self.pollination in P. hybtidn, floral metabolites flow away from the flowers, whereas in compatible pollination the ovary continues to be the major sink (Linskens. 1975). Deurenbcrg (1976, 1977) observed that ovaries of ~ 8 s e d and mlfcd flowers revealed differences in proteins 12 hr after pollination.

8. INTERSPECIFIC INCOMPATIBILITY

During speciation and evolution, populations differentiate to such an extent that morphologiully, physiologically, and/or genetically each one becomes a distinct rntity warranting a unique tuonomic status. Reproductive isolation at wmc atage prevents p n e flow among them. and the t u a arc then described at incompatible with each other. In- tcrapccific incompatibiiity h u not been nudied an extensively u in- traspcific incompatibiiity. However, it M known that there is wme similarity between the two kinds ofincompatibility. PoUen tube growth may be inhibited in the style. as can be Ken in a mlf-pollinated pistil of a taxon with the gametophytic type of sell-incompatibility. In addition to the types of pollen inhibition met within elf-incompatible syaems, the incompatible t u u may reveal other phenomena. In spite of a normal pollen germination and pollen tube growth, feniliution between the two gametes may not occur; in the event of a normal fertilization the resulting hybrid zygote may collapse any time before it develops into an embryo or a seedling. Such a phenomenon may be due to lethality [e.g., Gerrlp'iun dnvidronii when u14 u a parent in e- with mom Gorrlpiwn tax. (Let. 1981)], genic dishmnony, in- eflicient endosperm w in w e d cues, or the failure of the embryo. In a few cases tbe hybrid d s and d i n p are formed, which then develop into planu, but thne ue nerilc due to meiotic irregularities, do not produce gametes, and m do not form fruit1 and d.

Sometimes species can k crrnmed in one direction only m d not in I& rcciproul h i o n . Such okcrvations have k d to tbe concept of "uniLtenl incompatibility" u a u g p m d by Hur iwn rad Darby (1955). In arcb i4luncca it h often found that the pinil of a ulf-com- ptible plant did not b.vc any inhibitory effect on the pollen of the =If-

ANCIOSPLRW INCOMPAIUlLlTY AND CROP tMPROVtWLNT 77

incompatible plant; the recipmcal cross. however, war nor r sucnsriul one. investig;tions on int&peci& cmsxs in N i c o f k ~ by Anderson m d de Winton (1931). followed up by Pmdey (1964. 19761, revealed that incompatibility in such use; w;s BovcrA;d by a gcn; that also efTected the self-incompatibility of the female parent. Munin 0968) concluded that unilateral incompatibility urd seli-incompatibility arc under the urne genetic control.

There ir now another school of thoughr that considers interspecific incompatibility as a separate function with no interference by thr facton controlling self-incompatibility. Hogenboom (1973), bascd on crosses between L. pcruvhum x Lyrcpnsiron tsrulmrum. suggested that the inhibition of L. urvlmlum pollen tubes in L, pmrvirvtvrn pistils was governed by loci different from those governing ~1f-incompatibility. From the same crosser dc Nettancoun tt al. (1 974) arrived at a dinerent inference-that loci inhibiting pollen tube growth in this cross are either dosely linked to or w allelic to the S locus.

Interspecific incompatibility is believed to bc controUed by one gene or a group of genes and is often accompanied by zygotic and postzy- gotic inviability. Therefore, based on dme and site oiincompadbility, one or more of the followinn methods have to be critiullv xlected for creation of new hybrids, u k a s been done in several ux; in the past. It h a to be emphasized that the determination oi the cause of incompatibility is an essential prerequisite for deciding upon or developing a method for combining the two parental genomes. Some of these methods are indicated in Tables I-IV for some well-known crosses m- tempted in the paw.

A. THE EARLY METHODS

The earlv realization that the a i m a or the stvle acted a~ the barrier to foreign &en prompted certain rurgiul m;thods. T h e e surgical methods evolved from the observation bv lost (19071 that truuvenelv cut mryles of two tp&cice, when placed end ;o end in.& form ofa g r a ~ , did pennit the growth of pollen tubes. With refmemmts, this method w u ~ c c e u f u l l y applied to uoun that invdved heternstylour parents. It ir believed that pdlen g k n r of long-styled plants have porendality for longer growth ( R m p w m y , 1963). For eumpk, pollen p i n s of N i d u w puricu&a (wbose stylu M 2-3 mm long) ue nor ~ c m s f u l when d u d on the nyles ( - 10 mm) of NicorLM wtk, whercu the r a c i p d crar w u r u ~ f u l (wr Rulpuwuny, 1963). Such incom-

78 D.C. MSTRI

patibility was overcome by grafting by Gardella (1950) in &fur# and by Davies (1957) in Myur. Elegant grafting experiments by Hechc (1960, 1964), in 0. a g o m i r revealed that self.incompatibility in this taxon could be ovemamc by grafting a stigmatic part (compatible with pollen grains) onto a stylar part (incornpatibile with pollen grains). Fortunately, the flowcn and pistils in Omodna are large enough for such manipulations to be feasible. Similar cxperimentw by Straub in Plluni. uiokta indicated that in a ga i t of compatible-incompatiMe atylar tissues, length of the compatible partner determined the extent of ~ollen tube m w t h in the incom~atibie Dartner (Straub. 1946. 1947).

These meihods achieved a 11111; more kfinem&n In the experimen;s of Swaminathen (19551, who recommended the subwitution ofthc nat- . . urd stigma (causing incompatibility) with an agar-sucrose-gelatin me. dium on the cut end of the pirtil. Swaminathan and Murty (1957) rucmded in making crosses in otherwise incompatible combinations in Nicothna and SoLnum It was later realized h a t rurgkal operations m not always necessary; in Brorrico and P~funiu the stigma done, or with some style. can be simply removed and self-pollen dusted on the cut ends to obtain fruits and seeds (m Maherwari, 1950; Frankel and Galun. 1977). In fact, in B. aloacm injury of the atigma by a stnl wire brush is enough to break self-incompatibility (Roggcn and van Dijk, 1972).

8. BUD POLLINATION

The idea of bud pollination probably uoac from the realization that sigmatic accretion in mature flowen of some plants is inhibitory to self-pollen. The hct ha t in some t u a the mature stigmas are secretory and that the younger ones are not possibly prompted inwrtigationr on receptivity of immature pistils to incompatible pollen grains. One of the earliest of these w u Ihat of Yaauda (1934), who overcame self- incompatibility in P. rriokm by self-pollinating the buds; Attia (1950) alto succeeded i n this way wirh B. o I n m . Linskrns (1964) repeated the experiments of Yasuda with P. hybrida and found that the inhibition of incompatible pollen tubes w u directly proponiond to the age of the bud. Similar resulta were obtained when bud$ of Pdu& yt'lhi were incompatibly pollinated (Shivanna and Ranguwmy. 1969). It was also found that smearing the d g m u of buds with @tic exudate f m compatible mature Bowm incrwed the wcccu of bud Mi-pol- lirutioa (Shivmna d R a n p n v m y . 1969). In dl these audi i and in &ox on Niwdnno & ( P d e y , 1963; Bredemcijer, 1976) it mum

ANCIOSPERY INCOMPANIL1IY AND CROP IYPROMMCNT 79

be noted that the developmental stage of the pistil i8 critical for optimum results. Pandey (1963) found that in N, ah&, only buds at half the length of the mature flower responded to self-incompatible polli. nation; younger or older buds failed 10 do so. In the same species, Bredemeijer (1976) investigated pollen tube growth and pollen tube length in different stages of the pistils and found that in 3.5- m 5.5- cm-long buds the growth and length of compatible and incompatible pollen tubcs were comparable. It war only in the later stages of dc. velopmenr that the pistil was able to discriminate between the two kinds of pollen tubes. Thc results wcrc similar when pollinmted buds werc analyzed for reed number per fruit (Bredemeijer, 1976). Investigations on R , mtruw. Chtiranthu cluin; and Brnsrtca spp. led to similar obser- vations (Haruta, 1966; Shivanna rr a l . , 1978; Shivanna and Sastri, 1981).

There have been some attempts to explain these results. Bredemeijer (1976) attributed the success of bud pollination in N elam to the ab- unce of m pemxidaae i s ~ n t y m e (number 10) in the self-pollinated buds; this particular iaoenzyme has becn observed in relf.pollinated mature flowen, suggcning that it is involved in the rejection of the incompatible pollen t u b s (see also Bredemeljer and Blaas, 1975). It wan suggested earlier that substance8 uusing incompatibility are either ab~ent or arr not effective in immature pistils (Linskens, 1964). Nas- rdlah found that in immature rtiamas of Brasrice o h m . rotei ins re- sponsible for incompatibility eithe; were abaent or werc pre;ent in \,cry low concentrations (Nurallah. 1974. Nasrallah and Wdlace. 1967). The absence from buds of S-gene specific antigens being responribie for the success of bud pollination was also supported by studies of Shi- vanna n d. (1978) from their studies on R a p L n w and Cki ranthu . Frac- tionation of stigmatic exuacts by iwlcctric focusing dm revealed that the= are indeed some frictions present in the mature stigmu that are abunt fmm the buds of B, o Inura and 8. campulru (Nirhio and Hinata, 1977; Hinata and Nishio, 1978; Roberts dal. , 1979). Such differencer werc dm a p p m n t in P. hybn'h (Sutri and Shivanna, 1980a; Herrero and Dickirwn, 198Oa; Sutri , 1981). Sutri and Shivanna (1980a) found that the pistils of buds showed wme protein bands th.1 were a h n t in the n u ~ n pinilr.

Mon of tbeu uudies have becn on u x a that respond to bud polli- nztion. and in JI inruaees only rlf*incompatibility has k e n over- mmc. A question that emerges is whether bud pollination can JK) be u t c n d d ro intenpecifu moues. At tbe moment it u dificult to anrwer t h i s ' k u u r receptiviry of b u d in r v e d uxl has yet to be inved- gated. In #mne uxa it u known that buds uc impable of accepting

even compatible pollen, for example. Siqiro lh (Shivanna a d . 1978), L hg~j?omm (hrcher m d Peloquin, 1966a), Cn'num vixum, Amryilir ~itbzfa (Shivulna and Sutri , 1981). Sacchumm b r n p h r r (Sastri and Shi. vanna. 1979), and Awhu hypogam (D. C. Sutri, unpublished). In these and other uxa in which buds are not receptive or are poorly receptive. it has to be seen whether smearing the bud stigma with a medium such as exudate from mature atigmar (Shivanna and Rangarwm~y.. 1969). another extract (Frimmel, 1956), or r synthetic medium that is known to stimulate pollen germination can be of any help. However, Knott and Dvorak (1976) have suggested the pouibility of using bud polli. nation in interspecific incompatible pollination.

C APPLICATION OF P U N T GROWTH REOULATORS

It is a well.recognized and accepted fact that, like other morpho- genetic phenomena, the postfenilization changes leading to fruit formation are also under the influence of plant growth regulators, either in a sequence, independently, or in combination (Nitsch, 1952). Elu- cidation of hormonal regulation of fruit and reed development h u been largely m academic intereat. Also, the knowledge of these upects is limited to such a s m d number of tura that it is impossible to conceive a widely applicable hypothesis. Diversity in fruits is too great to war. rant a general concept on hormonal regulation of fruit and m d development. However, a careful investigation of the postpollination events does reveal chat these u e under hormonal control. For example, Gilisren (1976) suggested that in P hybrida differences in the floral wilt. ing rates between compatible and incompatible pollinations are due to the style, which causes pollination-specific changes in the hormone me- tabolism. Sa~t r i and Shivanna (1978) funher showed that such changes in Prrunio can be revened by dtering the kind of pollination. Self-in. compatibly pollinated pistils of P, hybtih, when pollinated compatibly up to a cenain time, can form pods and seeds (Sanri and Shivmna. 1978). Incidentally, Hall and Forrych (1967) observed chat among d the floral pans, the stigma and style released the greatest amount of ethylene, a g y o u s hormone d o ~ l y linked with wilting and ripening pmesws of flowers and fruits. It is also known that the changes in the flower due to incompatible pollinations are similar to those of m e s - cencc m d abrcision. In fact, in some of the early anemptr, hormones were used to prolong the life of the flower, thereby effecting fenilia. tion m d preventing the Uoml abscission (we Rurpwamy, 1963). 11 u therefore n ~ x u v y to find which hormonu pmmae fruit devdop-

2 . H m m and inlmplrf i k c w i b i l i ( y Achievement of pear x apple hybridization due to hormone appli-

cation marked the firm step (Crane and Marks, 1952; Bmck, 1954) and stimulated a xriesofother investigations, iirany successful but some unsuccessful. B.Naphthoxvacetic acid aoulied to the mtimna ~mmoled succeuful germinaiion of'incompat~ble'&allen an mterlpeckc crorser in Tnkllrm (Evans and Denward. 1955) D~onnc (19581 aonlled admo of (2:4-dich~omphenoxy).cetic aiid (3-6 ppm) t i ova;i4'24 hr aft& intenpccific pollination in Blanum and obtained normal fruits and seeds. Incompatibility berwun Photmlus vulgaris and Phmlus clrutfoliu was overcome by applying a mixture of naphthalene acetarnide and potusium gibberellate (At Yuiri and Coyne, 1964). Nico~iam npondo waa crossed with Nirotiuna fabaturn by applying a lanolin paste of IAA (PittageUi and Stavely, 1975). Hybrid in the cross Corchorw r~zprvlarir x Corckorvr olitoriu was not obtained until 300 ppm of I M was applied to the pedicel% of flowers (Idam, 1964).

Hormone application was also used successfully for certain intergeneric crosxs. By an application of ?,+-dimethylmine followed by an application of gibberellin, Kruae (1974) demonstrated that Hordrum species could be crossed wkh species of Avmn, Phkm, h ' y l i s , Alopr- NW, Tritium, Lolium, and Falua. Bajq d al. (1980) obtained cultur- able embryos in the cross Hmknrm uulgan x h a t e m b by bathing pollinated spikes in a solution of a mixture of gibberellin (25 ppm) and kinetin (0.5 ppm) solution. Laner and Enns (1960) had found that gibberellic acid pmmoted better development of hybrid barley embryos in uiw. It was alto found that a combination of gibberellic acid (25 ppm) and IAA (1 ppm) pmmoted pollen tube growth and ovary de. velopment in barley (44 x rye ( 2 4 croa~s ( k n e r and Chaubey, 1965). Successful use of gibberellic acid (75 ppm) in an H. uulgarc x Hordnvn bulborum cross ( S u b r h a n y a m and Kuha, 1971) was dem. onstrated in a range of interspecific crosses in H o r h m (Subrahman- y m , 1979). Pickering (1979, 1980), however, was not successful in getting hybrids in an H. d m X H , bulbosum emu. Postpollination treatments of gibberellic acid (75 ppm) gave rucees#ful results in Agto.

jwm x Ttiticm &ium (Alonro and Kimhr , 1980), barley x wheat (Fcdak, 1978; klm rf a!., 1976), T. erstbmrn X E l w gi-

pmhrr (Mujee5-Kui and Rodriguez, 1980), and H. m Q r t X T. nrr- riuum (Mujub-Kazi, 1981). Mujub-K.zi and Rodriguez (1982) conrider that in addition to a postpollination treatment, m prepoIlina- tion ippliution of 2,4-dimethylunine as given by K r u x (1974) wuld hclp in obtaining r e d s from bukcmsua in H , tn+~e x E l p con-

ANQl-M INCOU~ATIIILIW AND CROP IMPIOYIMLHT 83

&NU hybrids. The author's recent wperienm has shown that hormones, paniculsrly gibbcrtllin and kinetin, can be used in interrwtional incompatible crosses in the gcnua Ararhu (Singh d a/., 1980; Ssrtri and Moss, 1982; Sutri d d,, 1981, 1982). These t~udies, dong with othcn (Table I), therefore indicale that hormones have

T ~ l r r I . Ur d honnontr for hybridization in incompatible crosses

Cmsv Hormone used R a k r e n m

A n r h h p p o p X A n r h u np P.I. No. 276213

A X Amhis l*. b & -

A . A m x AvvhL puilh A IJPIgam x A n o l u sp. Coll No. 9649

A w k u mnlrrolo X Amhi t rp P.I. No 276293 .

C o r r h sliroriu x Cmhr. NI Up1YL"i

HibLru ~ R H ~ I I Y X Hibb. Ni &rfla

Hadnvn X AbpINtw. HOP lum X A m . H o h m x Dulyl,,, H&m x Fufy., Hordna x &I. ium, Hndrvn x r*bu.

Horhvn X Tnwn

Cibkmllic acid

Gibberellie acid, kinetan, 1.r.aphthylacrtic acid, indoleamtc acid, I.naphlylacetic wid

CibkmUir u i d

Gibbrrcnic u i d + kine. tin

Oibbcrrilir wid

I n d o k t i c acid

(2.4.Dichlorophenuxy). ucth wid

b .Naphhxyue tk acid

Alonso md K i m k r (1980)

S.mi and MOII (1981); Su l r i a dl. (1981)

Singh d el. (1980)

Kuwada and Mabuchi (1976)

Krule (1974)

Fed& (1978); Islam n .I (1975)

PittngeII~ and Stavely (1975)

Al Yuiri and Coync (1960

B r d (1954); C m c and Nar lu (1952)

Dianne (19X)

pmfitably been used in some interspecific and intcrgencric incornpat. ible crosses. It is not yet clear u to what is the precise role of the hormone used in such investigations. There are .uggertions that in inrtmcer of retarded pollen tube powth and prclnilization abscission of the flower, hormones maintain the f low? until the pollen tubes have p w n b n g enough to discharge the m d e gametes in the vicinity of the fcmde gametes: it is d r o suggested that hormoncr may rcimulatc the incompatible pollen lube powth in the pistils io that fenili%ation u n take place befom the flower h u abrcirsed, but the hybrod zygote obtained this way may not develop any further or may not develop fully. In such carer embryos from immature fruits havc to be excised and ~ I t u r r d for raising hybrid plants. l s l m (1961) had to combinc hormonc treatment with embryo culture for interspecific hybridization in CorcArrw. Similarly, Bajaj el d (1980) had to culture embryos from a few developing ovariel an Horkum spikes after they were pollinated with &aL and treated with hormones Napicr and Walton (1981) spraycd the spikes ofAppymn epecies with an aqucous solution ofgib- bcrcllir acid (50 ppm), naphthdcnsaiet~c acid (50 ppm), and 6 - ( 7 . 7 dimerhylailj~a!nino)purinn on drernarc days until hanrbc and ob. taincd less than 10% fruitr from 15 interspecific crosser, and embryos from them had to be ~ul tvred to obtain the hybrid plants In some interspecific incompatible crosser in Arnchis, hormone treatments slim. ulnte no-d postpollination changer but only to a certain extent and not to maturity; in fact, ovule, develop very slowly m d from them embryor have to bc cultured to obtain hybrid plants (Saatri d a/. , 1981. 1982; Sartri and Moss. 1982).

Different methods of hormone application were used. A hormonc may be applied u a sprw (u an aqueous solution, wirh or without wetung agmt), injected, or applied in Ianolm. or 8 solution may be .oolned to corron w r a o a d uound the o v w More than one andi - ZAon may be ncccsa&. Islam (1964) obwked for Corthow cGim;len that lanolin application w u better than wrapping the pedicel wirh cotron piece s o k e d in s hormone lolution. In contrast to this Bajaj dd (1980) found tbt wrapping spikes of Horkum with hormone-wet tcd cotton led to fun@ inkction and therefore w u inferior to the method of bathing the spikes in hormone solution.

Obvioudy, (Nit urd u e d morphogenesir is a complex pmccrs and is under a complex regulation, and it is still roa a r l y to attribute precise roles to hormones in such a pmcctr. However, them has recently been p a t interest in rhc mle of hormones in fruit development. It h a s long been known that ccruin hormones us produced in developing fruiu and &. of m y m c i n md t b t lec& are the major m r c c s

of the- honnonn (Nrsch. 1952). Cyrokinins, for examplc (Burror. m d Carr, 1970. Smirb m d van S u d m . 1979). ue m m s t r d to ntim- ulate both the NU divisim m d the u lmi la t e demand m cmwin. e m bymnic tissue.. In ckvdoping L p L u .Ibw d s . the endol&-& i s rich in cytokinin, and this I d Davey m d van Staden (1979) to ruggc.1 that the embryo dcpcrrds upon this cytokinin for its growth. Bcnnici m d Cionini (1979) also suggested that them war a cytokinin =quire- menr by young embryos of MYI c ~ m ' u y . It has 480 been sho~vn that in intenpecific v m u a in A)umlw, endpspcrm docs not dcvclop normally m d hu much lower kvelr of cytokinins than does endo~perrn from .elf-pollinationm (Nculing and Morrim. 1979). Cytokinin levels seem to be critiul for a n o m l l embryo development. However. whether an exogenous supply ofcytokinin in this cross cm prevent the embryo dcgencntion m d pmmotc its g m w h i* a matter 'till to be investigated.

D R M P E U T V R E AND INCOMPATIPlLITY

Temperature is kn& to be m important factor in induction of flowering in a l u g e number of uxa ( W m i n g and Phillips, 1978), but relatively little is *novn about its role in floral changer leading to fruit formation. High ternpuatums known to d u r n pollen viability (see S h i v m a a of., 1979; Stanley and tinsken., 1974; Johri and Vasil, 1961: Johri d d.. 1977). and low temperature* have been known to prolong the life of pollen grains. High or low temperature. 4.o smure poor pollen germination m d poor pollen tube grewth (Savitri a .I., 1980; Kuo n d., 1981).

In the m n t u t of incompatibility. m d self-incompatibility in particular, them have been .omc -ru in which ucid flowers were pollinated m d incubated ar djrrercnt tempemrums for investigations of poUen behavior. h t e r , intact Dowen on the plants rere 4.o subjcmed to temperature effects. Althou@ there L a lack of knowledge of the m u h a n l r n s of tbc effm of tempemturr either on the pollen or on the pistil, hiph tempc+tum h v e bw .horn h m feu inrunces to weaken or break down ulf-inmmpuibili~y, particularly -ercpllytic self-in- mmpribility.

In 0. w i r and Aru -.on. d-incompatible tubes grew weU at 15°C, but r e m inh- b e thu tempera- ( h i . . 1942). In Chwlhmo 7-, horevcr. inrmnpuib* poUen ~ b e s mt n& .I- f e e d by tbc range of t cmpenNru invenipted (10-S9°C), but com- puible N& frnau hi* runpuuurn (Bdi and Hccht. 1965).

O n o h orzauwu pistils nretreated with hot water at 50°C for 5 min failed to ~iacriminate &mpatiblc from incompatible pollen tuber (Hecht. 1964). Bali (1969) made similar 0 b ~ r ~ a t i 0 n S on 0. dombik&Ia ;nd also fourid th.1 for thi inactivation ofthe incompatibility rca;tion, the ~oll inuionr had to be done immediatelv after treatment. otherwise . - ~ ~ - - the ireated pistils would gradually recove; the ability to discriminUte between compatible and incompatible pollen tubes. Kwack (1965) showed that similar pretreatment of 0. ownmsu pistils for even 3 min weakened the incompatibility reaction buc pretreatment for 5 rnin wan more eflectivc. Lilium loq~$orum pirtila (both detached and intact) re- acted similarly. With increase in temperatures, detached pistils of L . l o m h s u p ~ n e d better amwth of self-incom~atiblc wllen. io much so-;hat ab0VC'39~C incompatible and compatible poilen tuber were indiatineuishablc (Aacher and Pelmuin. 1966b). but incubation at 39% drd not ove&ome interspecific 'incompatibiiity (Ascher and Pel. wuin . 1970). A oretreatment for 6 min in hot water a~ 50°C was found - -~ - - to'be bptim;m ior the best growth of self-incompatible pollen tubes. and highcr temperature8 (even 55°C) adversely affected both the compatible and incompatible pollen tubes (Hopper # ol. , 1%7). Tn;oburn hybridurn showed elf-incompatibility at lower temperatures (Town. lend. 1968). Self.incomwtibilitv in Trifolium war dro weakened at 40°C ( ~ e n d d l . 1968). l t k u found that ikcompatiblc pollen tube, grew l o n ~ e r in stvlcs of T bmfmst flowen that were develoned at 40% than in & o e dc;eloped a i 2 5 0 ~ (Kendall and Taylor, 19k9).

In Petunia =If-incompatibility was overcome by higher temperature: (Straub. 1958; Takahashi, 1973; Linskcna. 1975). Furthermore, in P. h y W it w u shown that incompatible pollen grains that were developed at higher temperaturea prior to pollination produced longer pol- k n tuber than those that were developed at lower temperatures (van Herpc11 and L i e m , 1981). Incubationr of fresh anthen in petri dishes at 40% for 60 to 90 min, or at 50 OC lor 30 and 60 min, with or without a ~ r i o r subzero temperature treatment (-20°C for 24 hr) were eflectiv; in breaking =if-incompatibility in' Lilium bn~iflorvk (M,atsubara, 1980). Matsubara found that treatment for a shorter du- mtton was more effective in producing wed. Coupling high-tempera- mre treatment with -20°C treatment for 24 hr nroduud a hiuh krcenta,qe of fruiu whoe aced8 were heavier than' thm formed i n fruiu after compatible pollinations. The temperature treaunents we;. found IO be mom d f i c i o u s than application of a floral organ extract to tbe nigma (Mauubara, 1981).

Temperature k therefore an important factor that w alter incompatibility. For tom masons thermal inactivation dincompatibility bar

largely been confined to elf-incompatibility in Bwrica spp. (Virser, 1977). C&sedrmum np. (Ronald and Ascher. 1975). Nnnrsia shrwsa (Campbell and Axher. 1972), Ornotha spp., Pefunb rp., R. ~ f i v u r (Mairubrra, 1980). and Tntlium app. Even in these tax& genotypes sensitive or insensitive to temperaturn treatments have been recog. nired. In wme i n n u r m or intcnpecific incompatibility, heat treat. ments have k n given but the results have not been encouraging. In wme interspecific cmues in Brcuriccr, Robbelen (1960) found 15*C to be the optimum temperature for pollen germination. BUI investign. tions on crosses between 6. cmplrhj and B. o l m r ~ revealed rl1at 25% was better than lSeC not only for pollen germination, but also for growth of the pollen tubes, some of them even reaching ovules (Mat- suzawa, 1977).

E R E C f f i N l T l O N POLLEN A N D 1NCOMPATIBILl7Y

The "recognition pollen effect." also called the mentor pollen effect, has evolved in principle from Michurin's (1950) work. A mixture of comuatible and incomuatible d e n on a s t ima had a atimulatow ef. fect on incompatible pollen his phenomenon was also observed by Glendinnine (1960). Wu (1955). Tsirsin (19621. Sulshima (19641, and other6 free ~ a m u l " a ol.; 1979). A deinite Ale of mentdr polien in incompatible crosses w u dvilied when Stetder (1968) produced hybrids between incompatible poplar species by mixing live incompatible pollen with .I-irradiated (killed) compatible pollen. The realization that the pellen wall is a physiologically active nructure (Tsinger and Pe. trovskaya-Baranova, 1961) led Knox a d. (1972a,b) to propoae a workable hypothesir for overcoming incompatibility and to illustrate this by repeating Stetdu's (1968) hybridization experiments on the cross, Pepdu &hides X dba.

In this method, pollen grains of a compatible parent u e killed and mixed with live incompatible pollen grains before pollination. The in. viable pollen is called recognition (or mentor) pollen. The killing of the compatible pollen haa been achieved in variour ways. The pollen grains have been scored (Knox d al., 1972a,b; Sastri and Shivanna, 1976a, 1980b), f r w n md thawed repeatedly (Knox rr al.,l9i2b), treated with anhvdmus methanol (Knox a al., 1972b: Sastri and Shim vanna, 1976a,b, 1980b; Taylor #Id., 1980), or irradiated with lethal doses o f 7 rays (Stetder, 1968; Knox a d., 1972.; Stetrler and Guries. 1976; Curies. 1978; Runvlu #I d., 1979; Howlett d a/., 1975; Stcrtler a al.,. 1980).

I h e ruccesr of r irndiated pollen u mentor pollen was Bnt demonstrated by Stenler(1968) in the infenpecific cross ktwecn P. &lfoider m d P. o h . Populu dbd pollen does not even germinate on the stigma of P, &&oi&s, hena the incumptibiiity ktween the two species. 7. Irradiated pollen grains of P. &/&& mixed with live pollen grains of ' olbo apparently stimulate the incompatible pollcn grains to germi. nrte on the stigma, kading finally to formarion of fruits andxeds in this intcrspecific .nd otherwise incompatible cross (Srettler, 1968). Knox a d (1972.. 1972b) repeated this cross and obtained hybrids not only by the use of -I-irdiated compariblc pollen mixed with live incompatible pollen, bur also by the use of other methods to inactivarc the compatible pollen. They found that Itorage at normal temperature, or repeatedly freezing and thawing the compatible pollen, was dro an effective mcans of prepwing mentor pollen (Knox d nl. , 197211). Cosmos bipinnatw and R, r&'uut, t u a with the sporophytic type of aelf-incompatibility, are examples wherein the incompatible pollen is inhibited on the stigma.

Subsequently, it war shown that gunetophytic rell-incompatibiliry could also be overcome by using methmol-treated compatible pollen as mentor pollen in P. hy6nifa (Sutri m d Shivmna, 1976a, 1980b) and by using y-irradiated pollen in N. & (Runulu #I., 1979). Dayton (1974) had demonrmted that this method could be succcrafully adopted for overcoming gamnophytic self-incompatibility in apple dso. How. ever, in apple, pear, and their crosres, mentor pollen prepared either by methanol treatment or by y irradiation w u found to be ineffective (Visser, 1981). 11 &odd be mentioned that in P. hybrib, self-pollination of buds produced a higher percentage of fruits with a larger number of seeds than were produced by the mentor pollen method (see Shivmna and Rmguwuny, 1969: Sastri and Shivanna, :980b). Fur- thermore, in a smnly rlf-incompatible plant auch as P, hybrib, mentor pollen prepared by methanol vutment w u found to be ineffective, but its leachate, when applied to the stigma before self-incompatible pollination, gave a low percentage of fruits and the number of seeds r t per capsule w u mmprnble to that obtained by ~cJf.pollination of buds (Sutri and Shivanm, 1980b). In mother w o n , N, rlrm, with gt~erophyticdf-inwmptib'fity, the number of 4 s formed per fruit w u much greater after bud pollbtion ( m Brcdemeijer, 1976) than w u obtained by poiihting the maorre n igmu with a mixturt of menlor pollen m d inco~mptible pollen ( m h u l u d d, 1979).

EfXicncy of this mnbod hu k e n a u n i n e d in wme interspecific in- wmpuiblc crosses. In Cwair, in uch d the crouer investigated,

ANClWUM I ~ M P A l T N U l Y AND CROP 1HPROV.MINT 89

abwt 50% of llowen pollinated with polkn mixture produced fruits. In dl but one cross combination, ovules were larger, with well.formed embryo ua and dobufu embyror, in Eonmn to untreated incompatible pollinations, which did nM r t any fruits (den Nija and Oon, 1980). In Su- inlLvrn X &mum nu*prrolm. r e m i t i o n pollen p r e p a d by methand crc~mreat of compat~ble pollen stimulated gcr. mination of incompatible polkn on the stigma a# well u penetration into the nigmatic tirrues ( S d and S h i v m a , 1976.). In this cmas, however, no h i t s were obtained &use the incompatibk pollen rubes chat entered and the t tylu tinm were not normal and were loon in. hibited (Surri m d Shivanna, 1976.).

There uc repom that mentor p d k n w u ineffective in overcoming df-incompatibility in B, rrrmprtbir (Sutri and Shivmna, 1980b), 0. qmmis, m d a hybrid benmn L. u&m x L. pmruianum (Ra- mulu d d , 1979) and in overcoming inferspecific incompatibility in eight creme1 of I- (Curies. 1978), Tn$alin (Taylor d el.. 198O), and F u k n onrndinacm X hbIL ~lavrors (Marrk, 1981).

Although there .rr only a few cues in which different methoda of preparing mentor pollen have beor uud in the u m e rpecin, there ue innmcet in which use of a specific method is crucial to the success in overcoming incompatibility. Self-incompatibility in R. ~etiour can be overcome by wing the mentor pollen pnpued by nongc but not t h a ~ obuined by m e h d treatment (Sutri and Shivmna, 1980b). The mentor pollen prepared either by s tomp or by methanol treatment w u no! effiuciow in overcaniag df-incompatibility in B. l.mp.shis ( S a d and S h i v m a . 1980b), but Roggen (1975) tucmded with a dated rpecies, B. ohacru, by wing compatible poUcn luchate on the aigma before elf-pollination. Differences in the efficacy of method# for prrpuing recognition polkn were also evident in P. hybida. In a ttmngly elf-incompatible p l a , methanol-truted mentor pollen w u not effective, but the compatible poUen luchates were effective in overcoming alf-incompatibility (Sutri and Shivmnr, 1980b). The com- pacible pollen leaclucea were u effective u the mentor pollen prepared by n m g e . by repeated freezing and thawing, by .I irradiation, or by mech.nol treatment in overtomkg intcr8peciRc incompatibility in Pop. IJw (Knox d d., 1972a,b) d self-incompatibility in C, bipinnutur (Howkn a .I., 1975). It may be mentioned here that the incompatible wUen W t e a w e n able to dicit reimion d n in i&wb n i m a b p i l k (in the form of d o s e &pmiu) jun u the incompatible poien prioldo(IihlopHambmdd., 1974). It u therefore cuggeskd that for mentor pol*n co be c&scive in ovuwmkq iocompatibility, the mnh-

odr for its ~mduction have to be iudicioudv dectcd. In instances in which onlyonc method has been thcd and f&nd unsuccerdul, mentor d e n ~ r c ~ u c d bv other methods hould be tried.

~ h ; n &em h.b been N C C ~ (Table II), it has been attributed to rhc early interaction b e ~ n pollen and pistil (Knox rt a l , 19728). Stettkr n d. (1980) reexamined rhe mentor pollen effects in some incompatible cmues of species belonging to thrcc of the five lcctions of the pnuw Ibpulur. They suggested that rhe success is due J w to the k t that ovule and ovvy arc somehow stimulated by killed compatible pollen but not by incompatible pollen. That pollimtion provides a aimulur ir evident from urperirnenrr of llliet (1974), who obtained haploids h m pollinated p i d s of Popdm treated with toluidine blue. This dye m a t e d the pollen tube growth halfway through the nylcs and still the ovaries developed: , .IIK nrcngth of incompatib~lrty and the extent of crolubility of a

parent that is the source of mentor pollen uc other critical fmocton for

i ~ u t r i ud Shi- v.nru. 1980by'

BLowm. 1975Y

Puhua *-#--, (sari d sh,.

vuma. 198%)''

M& (byton . 1971r P d u u hyb&

(%mi and Shivma. 1976bYe

N w L I P & (?+. 197S, 1977; Rmulu a .I, 1979y

AN^ (D. C . Sum, tan. plblirhrdr

C.rau (dm N i i ud 0011, l w y

~emr . Pandey (1977, 1979) reponed that mentor pollen had a pm- motive effm in individuals with weak inmmpatibility but not in individuals with nmng incompatibility.

7-hVwbted P d h E d a m tram* . ~ n e m p t h g to o v e k m e inMmpatibdity in N. a k a by the use of 7- irradiated ~ollen (100 krad Go). Pandev (1975. 1978, 1980) obtained lome unuiud rc;ulta in addition to ovcr&ming self-incompatibility. He o k r v c d that certain characten were truufermd by mentor poUen and this p- h u been ulled a apecidlcd fonn of "sexud trans- genmia." Pandey (1975, 1979) suggested that a high dore of ionizing radiation cruuformr the generative nudeus into a number of small chromatin fngmentr. and thia w u confirmed by Grant n d. (1980). It w u alw, h w n that there is a I u k of metaphue orientation and the failure of division of the generative nudeus during in ~ i h o germination of the imdiated pollen grains. By using t h i ~ method a s m d number of diploid pmseny were obtained &at resembled the female parent in a majority of c h u u t e n but rhowed a few characten from the parent of the irradiated pollen. Jinks n d. (198)) have repeated Pandey's ex- perimenu in the u m e tpceier and have arrived at similu conclusions, ~ggcat ing a novel method for m mu0 tranrgenoris. These obmations have opened a new method for incorporation of Kgments of paternd cbromoromes into the m a t e d genome, thereby vradorming the Iar-

F IMMUNOSUPPRESSANTS AND INCOMPATIRLPN

&tea and a-worken pioneered a novel concept in the light of pot- sibilides of wide hybridization. Baaed on ocher reports that there are lome orp-specific antigens (Wright, 1960) and on the cxisunee of phytohenugglutinins in plants, Bates and Deyos (1973) ~uggcsted the exinen- d an immune mution andoeous to that acvmnlr in animal Byrrems. Tby uUcd chis "nereoapccilc inhibition rrueti&" (SIR), but there u nilt no dirm &dance for the existence d SIR in mlants. However, tby iniriued wide hybridization exprimenu in whi& ceruin mimd-d8cclive imm-ppreurrnu were uud. Thcr were t- uninoupmic &id (eACA), ehloruapheniml, d f l a v i n , salicylic wid, and genrWc acid. Success n t n varied unong immunosuppreuanu, eACA W i g the molt eaective. The m d t a obtained have not only ~ p p o r ~ e d the bypthe*. upon which thee trials were initiated, but krvc dm suggested no* ways d brukhg the intvrpccific uwvbility b . r r * n . T h e c r a r c l i n w h i & e a r b y o l w a e o b u i D c d w a e d u r u m

wheat X m, barley X we, .&ley X triticde, buley X oats, and maize x wghurn (Bates n d., 1974). In the untreated contml~ even fertilization w u not obxrved. Bate: n ol alto rcponcd that progeny from M e y X rye, durum whut X M e y , and biead whut x b h e ; have been &meed to F, generation8.

The rcmltl (ace Barer. 1974) with this novel emu^ of chemicals did nimulate a kw' other w o r k e n , ~ d a few report; puhirhed to date arc enmuramnu. Tiara m d Lmer (1977a.b) observed that eACA nimu. lared ckbbyo development in ~ k ~ u r n h;&m X S. m l r cmeus. In dl thew experiments the immunorupprusant rolution wan applied to tbe l e d uils a few m k s before pollination.

In tbe interspecific cmss between V i p r&u and V i g ~ urnbriku, tACA (100 pprn) applied u a Folk :pray to h e aced parent w u twice .r eBcctive .I the untreated mntmla ( h i m Vcptable Research and Development Center, 1976). In the m e c m s Baker M d. (1975) found chat m injection of 250 ppm of eACA into the internode of maternal plants p v c optimum resulu. Faliar spray of tACA (100 ppm) applied for 14 day8 nur ing at, or earlier than, the premeiotic n a p of tlower devdooment to m o cultivan of V h m d h delaved but did not DE- vent embryo abortion in V --x V. unbr~ora'cm~m (Chen i t z i . , 19781. Embrvo abortion w J d d m be ~ r c v e n t d bv d e f o b t i n ~ the planis 4-6 diyr after pollination (Chen k d., 1978),'a pmadu& de- v e l d for P -mu X P, udrA crosser bv Ibnhim mnd Covne (19;s). More recently, ~ujecb-&i (1981) hu'shown that in ~ t & r n timphuii X S. cmL aunes. LACA aeaunent (concenttion not given) of T. t i m p h t i i Borrts for 4 days lher pdlirution d u d embrvo -rv from 90.5 to 18.9%. but inerurd the number of wa. &m w-ith both embryo and endaprm formation fbm 11.4 to 18%. In thi. W c u l u nos: Mujeeb-Kui h u dm shown rh.t crourbility is .tlenid by the envimnkmt in which the f e d p.rrnrr are grown md maintained. In F. d i k a X D. glonual~ emu, however, eACA a u t m e n t lmnantntion not riven) w& not effective (Matzk. 1981). Thor &id. will the &on of dg on a ~ & r number of uu. with mmetic iaoomwibiiiw: chmiulr with a i m h dtkP ue be uLd. A-better k ~ d i n g ' o f the mode of mion of tbne cbemiulr mum be obuined to i n c w the eirsnivcncn of their une in pmmoting other dnl.bk but i n c o m p m i cmsus.

ANDlOtPUY INCOHPATIaMY AND CROP lYPlOMMLNl 9.9

TAB= lIl MiutU-I m u h o d s in armminl tarupcih (SI) sr interrplcik (ISI) inmmptibilily

Typr or Mctbd Tuontcmrr inmmp.tibilitv Rcfemneer

N-m.Tdyphtb.lmic Bmxk &-'I IS1 wid, P-n-roly- x 8. o h m p h h l m t r i d

'20, Brvriu spp 51

Roggen u .I (1972)

Baler (1974). Bate1 uld De. ync. (1973)

Bate# u d (1974); Chrn a .I

Pmhly opened tl- of Bmr& q p . . when e x p o d to 3-5s COa. behaved u a&-cammtibk ta a certain extent. althaulm t h m were difference8 according' to the genotype or the species inv&tigated ( N a - .ni.hi #t d., 1969; N h i s h i and Hinrta, 1973). In 8. o h . uU- incompatibility w u d m overcome by "electric-aided poUimtion" in which UY eieetrie potential difference of 100 V w u applied k n m n pollen and nigma (Roggm d al., 1972). The eff~cacy of this method in this tuon . expressed u md number per pollination, ir comparabk to cb.1 obuined. by other methods, mu& u &apiuted pinil b~h- tion. bud pollination, chemical u u r m m u , and u r n p e r a m vucment. Ia inturpkific cmfin in Ayhu, ceruin o r p i c klvenu (ethyl .cc- rue cnd kXUK bring rhc morr cUutive o w ) were applied to Rignu and hybrid8 were &mined (Willing and Pryor. 1976).

H. QENmC AND CrrOLD2CAL MANIWLATION

~dnrr poUcn md nipma innnnions ur not the sole awn oi k o q d b i i , and there n a numkr of (*n& or yrolo@ul m- *arr for fdure u, produce hybrids or to achieve luceclthrl gene mru.

k r The* 4 k menttand bm0, before conrsdenng I* vvno methods. rhch have become tmponmt ~rrhntqucs for ,nrenpcrlfic transfer

DJierenrrs on n v m k r of chmmommrs d , o r alosdv dsffemnrrs tn . , Wo speckt tu be m:md un be rrmng facton, preventing hybridi. ution b m e t n them. The ura mvolvcd #my have the umc chro. momme number. mch u TifJlm npnu and TnNiua ombi- (Zn r 52) (Williuns, 1980), yet they cannot nonndly be cmlrd .

In many diploid X letraploid c m s n within or between v c i c s , the end-nn cohppu., causing csrly embryo .banion (Brink and Cmper, 1947). Johnston d d. (1980) proposed that in auch instances ploidy p r r i. not the pmbkm. According to them, .n abnomd rndospmr it due to a t i o n of maternd:p.tcrnd genome ratios fmm 2:I in the endoeperm. In this hypothesis the genome of each spe cier has lo be assigned a lpdfic *due for the endosperm, i m m ~ t i v e of the ploidy lcvclr of the puentd spcier. By manipul&nng these num- bcn, Johnston m d H-cman (1982) have sucmdcd in pmducing hybnds arxcco some dsplold s p c ~ c r of brnlum that canno! be cmseed othcrwnu. 11 appean that rrsulu fmm fcr tnlenpcafic cmers, such u %&*urn Cosrraum Lwoarrvon &turn md A m can k ex.

Elhinition ai&mmo&c~ of one of &a &nu it mother prob. Irm often enmuntmd in ridc cmncs. and this h u been pmfitlbly employed in pmduerion of hapbids in Hordnun (Subr.hm.nym, 1070> .-.-,.

Theu pmblemr have been tackkd largely by lmtcgic manipultion ofchmmaomc numben and ploidy levcl, lncreuc in ploidy level h u often been .chi& by using dchicinc and scndn h e r chnnids, whe- reduetion in doidv hu been achieved bv haoloid -no- genui. uld/or by antder lab pollen culture or by &;cbnnkd u u t - mcnts (mi", 1974).

Wbm w o t r u c-ot be hybridized, a dud tuon c-e with onc ofthem hu often been u r d as a bridge for wmdelcr of h u t e r ( 8 ) . Eumplo of luch bridge e n m a uc found in Nk&, l7ubm1 Cu. &, d Sdounn (n mi- b H d e y ud Opeashaw, 1980; SulLcr, 1980). The for p n i c mntml o f c r a d i i q ud c b - momme pliriap u h n d in T d h l h d d mnrintlc in orher plant au. C- lhaJd bc attempted with u many ~ c n * o n s u possible; -My rbe different d d v m a u v shm varying d i l i f y with m- bther drcies. Such M e - h& been ob~=.& in N. &.-m d-

ANCIOSPLLY INCOMPATUILIW AND CROP lYPLWLMINT 95

KrZ and are located on thc 58 chromo~ome. The dominant alleles of the* genes in genotypes such as in the variety Hope interfere with the pollen mbc growth in the miempyle in T ustiunm x S. c m l r (Jrlani, and M a r , 1980, 1981) and T rrl iuum X H bulborum (Snapc ct d , 1980) w a r s . The 5B chmmoaome of wheat also carries a gene (Ph) that mtricts ~ i r i n r . Bv eliminatinn this chromosome (Cauderon. 1979; ~hom.a', l98i) or by s ~ ~ ~ r c s r i ~ ~ the activity of the'ph gene by Amlobs ~ I r a i l a mnotvar (Rilev d e l . . 1968). it has been wssible to " , * " ,. ~ , increaae pairing and enhance recombieat~on between genomes.

Details oftheae and other upecta of genetic and cytologicd manipulations have been listed and diacus~d often and ur not presented here. The p a p n of Sulker (1980). Rees rial. (1981), Peloquin (1981), Hadley md Openhaw (1980). Thomu (1981). Riley rt d, (1981). and Driro11 (1981) uc suggested for conrultation.

The in mm methods are increuingly being recognized u regular techniques for the plant breeder inrereatcd in inrerapccific hybridization and in wercommg incompatibility. Advance8 in in v ih . techniques have k n pmviding opponunitiea for sexual hybridization and, more recently. for paruexual hybridization by protoplut fusion or for gene uansfer by plumids, liporomes, viruses, chromoromes, or otherwise.

Sexwl bhridiution-by these mcthoda e n c o m p u ~ a culture of ern- byol , ovules, or ovaries h m inwmpatible crones in which embryo# or ovules do not develop fully after wide hybridization by eonvmtiond meaaa. The fin1 auccnrful culture of embrvor w u from the ucna Linum p n w X Linum w m k u m (Laibach, 1929); then ur now over 40 cmucr in which hybrids have b a n obuined by culture of embryos (m R a m v a n , 1977, and Table W ) . In mwy inauncea. however, the embwo dcnenerates when it is too mall to bc dissected out for culture. In Ib;u &anon, ovule or ovuy culture facilitates hybrid production ( S t m m . 1981). Takcahiu d d. 119801 have e o m ~ u e d the effective- Leu of imbtyd &cure, ovuj. edmre,' and ovule'culture from wme i n t m p c i f ~ - involving apcdea of Brmica and R. r d i v w . They found &at in wme -a ovule culmn w u h e r Ih.n either embryo culmre or wuy culture; thh w u particularly uue when 8. &a w u OM of rbe pvcnu (Tabhim rr 4.. 1980). O d e r from inwnpccifis -a in Cojpi.rn ( S t m u t and Hnu, 1978) d wuia fmm inter- spec& cmua in h s k (Inoauu. 1978. 1979) have k e n culnurd m d hybridr okrined.

TALLI R). h e intcnpdsr hybrids by embrp rulrum'

CIov Re-

A.&p,-,X Th&m*nnia Gill n d (1981) urhrbrrr (&) X HnLa *I. Shiwobu and LLMDI~ (IPBI)

*rr (*., A r d u I- X Anrku sr. P.I. No. Sutn urd Mow (1982); Svtri a .I

276253 - (1981) E ( m w n v h n r X H..lamt& Mujrrb-Kul and Rodnguc; (1982) F . r m s a h v r X & + u & m a & Matzk (1976) H * u u e x H h d w Kurada .nd Mabusha (1976) Hu?eXHhnb&@d Kurd. and Mabuchd (1976) H h - X - 6 W d BML a d(19t4) lm#smw bduim X I- Ari8umt (1980) Wia pm*lr x F- mbm Niuuhe and Hcnnin~ (1976) h ..hr.luu x Lau brir I). IA Tsur a d 11978)

WIlll ( k u * u r r . X (k-nnpnuw Willurns and D. h Tour 11980. . . . .

1981) S . h a n v b . y n . X S d m a k k m a Shum. n d (1980)

mb- x T r i m h w Wimn (1980) mhjwm x a d rreiproul Williams (1978. 1960)

r . r q U X T . - William snd V y (1981) Tn- p@u x T q b k ~ ~ muiarr Phillip a d (1982)

'le mddition m cha. listed by R y h . v . n (1977).

Both fcmde m d mde m t o p h y t e r have been cultured together in dm, w rh.1 pdllution, fenil i t ion. uid ponfenilhtion changes kding to formation of hybrid d or m d l i n p are all achieved in the t a t tube ( R m g u w ~ y . 1977; Zenkteler wf Melchcn. 1978; Zcnk- t&r. 1980; Stnru t , 1981). Of 22 intcrpneric or intcnpecifrc corn- b i n a t i o ~ . 5 formed see& with viable embnw. 13 with immature cmbryw.'2 showed only endolpnn formation; A d 2 only fenilizari~n (ZenLteler. 19801. Tbe test-tube f e d t a t i o n is a refinement of rbc ex- &-&" bf &u and uwchres on succeuN i n m v u i r n pollina- tiom in wme memben of Papwer8a.c ( h u . 1960; M h h w u i m d m u , 1961). .

Another a p p d to exploit the in mm method# ia ro force the ksion of wmatic protoplutr m d provide conditionr for the growth uid dif- k t i u i o n of the heterokmyocyte. Luding to m u i c hybrih. Nu- meroua actcmpu, m ~ t n g e d by the initial - in h&g protopluu in the .tm.Uy compatible u in h n i . (Power d d , 1970) d Nicp ci.u (Cuiaon d d., 1971). h v e been made to produa mmatic hybrid# fmm d y incompuibk rpec*. (# Scbiedcr ud V d , IM). S i

-urr rweourmmu,m ANTI caor naraovu*urr 97

nifiuni mont these ia he wealion of "Ambi&bmssica" by fusing the p t a p l u c s o f - ~ d l d o p s i r and BrClllt~, F n e n of w o difiercnr i u o - nomic triber. & d y d m i h u n l ia chc fan that the metbods. w far ex- ploratory in nu-m ;nd-confined to mil worked out model rystems, ur nm k i n g extended to hybridization and improvement of crop ape- c i n ( W e n 4 n d.. 1979). In m r d other attempts at intenpcific and intergeneric .nd protoplast fusion, hybrid clllus liner have been ob- uincd (wc Schicder and Vuil, 1980; Gunborg II d., 1981; Cocking, 1981). Krumbiegel and Schiedu (1981) haw o b r m d that hybrids between D.hn inudo and Ampa buhhu ua k produced only by wmatic hybridization and not by other in d m method: suggested by R a n p m m y . . (1977) ~d Zenkdcr (1980). Hybrids b e t m n -N. I&-

mre produced by in o h KXU& methodr (Reed edd Collins, 1978) and bv mnutic haion lEvans d d.. 1981). Evans II al. (19821 cornwed &nc hybrids and observed that.mmatk hybrid doner'show;d a &eater range of v d i l i t y for certain rnorphologicd charactem than did the wxud hybrids. A commonly obrrved problem in such wide somatic hybridization ia the m u d lou of a put of or a rull genome of one of rhe parents (Duditr n d., 1980). Ex~r iment r of Subados n d. (1981) b d Cri;rb.ch a d. (1981) ~ g g & chromosome uptake by pro- toplam u another dtenutive to tnnsfer ofthe full genome by somatic &;ion. Upuke of chromoaomn or of their lcgmeitr un d m be fa- cilitated by encaprulatina them in lipommes before fusina the latter with the &ipieni proto&ts. This h u been shown by ~a-tthews and Crer (1981). Luquin (1981), .ad (1989). Utcmuively, the de- mired & m & t r of DN* can bc u m d f o ' d venom such u AFO- huhnm tunukkc Ti d v m i d or cauliflower m o d c v h s DNA, which may uunfe; the DNA to the bort cell for integration by its nudeu DNA. This h u been demonmated mcntly by Chilton d d. (1982) and &ens ad. (1982; u e d m reviews by Cocking n el., 1981; K d o and Kleinhofs, 1980).

Them ir a m g interm'in the use of wild relative# for reversing genetic e&n and for cenetic improvement of crupa. Wild species h.ve Jwayl kc. of eonkrn co &dcnu of biisynenutics, bur now they SIC d equd concern to p h t b m d e n . A knowledge of evolution

of wi& aoa and vik veru. A deeper r k into rherc i d u r n hu prwidcd mahdr Tor convutiug rome of chne info m w s r r . It u

bopd that these methods, with modifications m d improvement as nec- e w , will rtimulate new iku for the creation of hybrids that have m h; duded us.

It is ix ru idy not r u y to pick one of the methods u the best one. but ulf-incompatibility was &id to be overcome best by hxgh-temper. ature uutmenra (Townmd, 197 1). To break intenpecific barriers, a range of p8rentr have to be v m n e d for the most croupble one. and the tuture of ineompatibiliry-whether pre. or postfertiliration-has to be determined. Fluorescence m i c m r c o ~ ~ haa been a convenient method for determining this. This method artin in, 1959) facilitates h e observation of d e n tube growth through the pistil, which is pm- e d y not e u y by iight m ~ p i c c ta inG me&. Having determined the rite of the buricr. a rmw of ruirable method: hu to be adopted. The most common of theKmethod: have been dx:cu:nd in this u t ide . m d wirh greater understanding of the phenomena lnvolved more techniquer uc bound to emerge.

-

1 un p t e u cro Dr. J. P. M o u and I>T D McDonald for their comrncnln on the ankle d Miss C. S u m for Mp in pmpualion of the typeuripl.

Alonro, L. C., d Kimbcr. G. (1960). A hrploid be- A m J W N ~ end Zh. tinar u n y l ~ ~ ~ Cnrl Ra. Enar. I. 355-358.

Al Yuin, A,, and C-. D. P. (1964). Eff- dpwh re&ton in delaying pod .be iu iw urd anbno abortion in the inucnmecific crou Pludw vlJlorir x P ~~~ cmp &. 4; 433-435.

An*. E., urd dc Winton. D. (1931). The#enct8r ~ J y r i s o f u n u s r u l rela;ion.hxp b n n n rli.stcrility d dt.kni l iry in NLHvu Ann. Mo &I C.rd 18.97-116

A m . N. T. (1968). Self-inmmpuibiljty in .agiosio.prm~: A m i m . Cmir (Th He. p) SO, 1-24.

&mi. T. (1980). h simmlturr dcabryo. .nd wuln ofccnsin ineomp.tiblr wlh S d C- M M g I- 8pCCkS.J. A n h H a . Srr 105. 619-631.

Arbor. P. D.. .nd Pdoquin, 1 J. (1966s). ERcct d floral ae iny on chr p a h oi wpcibk 4 Lranpuibk pl*. rvbn in L i h b n # M . An. J, BM 53. 9s- ,#w .--.

P. D.. .ad Pcbquin. S. J. (1966b). Influence of rempnwre on ncomptible a d cumpuiblc polka rvbe pmnh in Lilim *yw. b. J kur W. I. 661-664.

&&r. P. 0.. rad ?rbquin. 5. J. (1970). Tcrnprnlurr md ulI.incompribilIty rc. vtiraisWir-.Tbmb.J.An.h. Hnr i r .& .U .Sb-580 .

A . i . a V r p u b * ~ d D e v r b p l l v n c C c n r u ( 1 9 7 6 ) . "PloFn, Repcmhr I975 (L(luybun)." pp. 3 3 4 . AVRDC. O&ahu. Taiwan. Rrplblis a i C h i ~ .

UIOIOlTUU f*EOYPASDILIW AND CROP 1YPB.OV.ULNT 09

. . sn, %. s.9-37i .

h. Y. P S.. V m a . M . M.. m d M u . M S (1980) Barley x rvc hybrids ( H e r ) lrm#b n n b y o culturn. C m Sn' 49, 962-369.

W c r . L. R., Chn. N. C . . uul Rt*. H. G,(1975). Effect ofan immunmupp-nt a ul inntMi lrc c- mf the n a u V u u Hnn 70. 425-333 -. . -. - . - - r.-~.~~ .~--. - -.- -.--. -- ~- -. . .....-..-

Mi. P. N. 11%!31. So- ummiraenul mud~" on thr rlf.~nmmmtibilitv of Ch&m n(n*qnh. N&I i k ~ m r ) PO. 97-103

&L. P N . 4 W d 1 . A (1965) The mncuc8 of rlf.mcommttbd~tv tn Ch&m . . rMiyu1. $6. 159-171. -

Barn, L. S. (1974). W& c-. A "Plllcadinp of T h e Worldwide Maar Im. pmrcmmt in l r 7 h m d the Role (or C IMMW." Vol. 5, pp 18-18

Bua. L. 6.. ud Deyoc, C. W. (1973). Wide hybndrution and remd improvement. Ea B d 27. 401-411

b t i . L-s . &p V A . R o d n v r . R R and Andcmon R G (1974) P w nr low& nwel arul y n s r h d So T.L, 19. 283-281, 286

k m o . A . ad Cuvun8 P C (1979) Cnoklntn* d rn m m dcvdo~mcnl o f h u . ~v a s r i u v e m b y a h m i47.17-29. B-jer. C . M. M . (1974). Pemridvl vlrvity and proxidu. isenrymr corn.

pairion in nlf-pdlbtd, cross.pdlinated and unpUirutd mrylcm oiNu01uu &. A N &r, hM ¶S, 119-157.

0. M M (1976) LIT= of bvd pollination and delayed rlFpoUmuion on the induction of 'possible m j m b pmriduc in .r*(b ol NMI- .ku A& &r. N n l 25, 107-116.

Brrdrnuijer. 0. M. M., uid B h . J. (1975). A pouible d r d r y h r pcmxid.r p.dimt in tk rrjmiDn of iommpuible w i n g pollen tuba A n &I Nnl 24. q7- .. - -.

B m b J r r . J. L. (1917). Pollen cytology and wsornp~ibility mtmu in plmu. J. H d a. 271-277.

I)mrb.*ar. J. L. (1967). The dhributh uid dpifi-ce or binurk.rc and uinu- &I= pDUcn CRin. & tk arqi01pamr. Am. J Ibr. 54. 1069-1083. he. J . L., d Kw*cC 8. H. (1%)). The eucntid rolc oidc ium ion in p&n

pnnimtion uul pollen tube fah. An. J. &r 50. 19-863. D M . R. A.. m d k r . D. C. (IIW71. Tb. ondolopm in red M o ~ m m t . &I. . .

Rn. 13, 42.9-541. Brinl, R. A,, Cooper, D. C.. d Ademwn. L. E. (19H). A hybrid bmn

H m & a j r b w ad Sa&rnrlr J Hmd Sd, 67-75. B d . R. D. (lB%). Ho rmone -Ldd pu-apple bybdds. H d e 1, 421-429. hnmn, W. J . . .Pd CUT, D. J. (1970). Cvi&inin content d p a ad. durinr heir pab a d k u c f o p ~ l . *r*l. k. U. 106+1070.

CsmpMI. R J.. h & r . P. D. (1972). High tsmpratuix remom rlr-incom. puibilify lo h m r . t w i g N w l . 1. 3-5.

Cuban, P. 5.. Smil . H. H.. md M g , R. D. (1972). P u u e x d ialenpsiFw pLDt h-. Bw M. Aul, h. U.S.A. 69. 2291-2294

Cmduar. Y. (1979). U r o(- species h r w h u ~ ~mprwe-I, h ''Dmsd. -8 IL.GB~Y h d C r & " ( ~ C. Znm md A M van Hmm. ad. ). pp 175-186. C.un br *SnoJrunl W i md Dorumcnutioo. W y m u y a

CLca N. C.. Curoa. J P . Juok. T.. W e r . L R .ud C&. P S (1978). b " ' d k d Iqumcl h uacmvedad mabda of

r h ''C M- Sympatua." pp 247-152. A m V a p ob* &rucb nd Dn+mml Clot-. shnhua. Tmrm. Republic d C h .

CUrm.Y .D .T rpbv .D A.P~.A.,D.rid.C..Cu.Whn,P,uulT.mp.

J . (1982). AFIrm.r r h i r v n n i n u n T-DNA lnao the *no- d hmt plant rmc elk Ncra (Lnlr) 295. +32334.

Cnckinr. E. C. (1981). 0wonunitl .r (rom thr u r d ~mcwdasta Phhr Tmu. R .k -Led". Sn sn -mo; 557-568

. . C a b = , E. C.. by, M. R., PtntJ. D ,and Power. J B. (1981). A.pxttdpIant

F ~ u n u r ~ p u h - NYV. f u r ) n s . 265-270 - C n n r . M B . ud Marks. E (1952) Peor-apple hybndr .Wml..n(f&mdea) 170. 1017 C m r . M . Cumpdm,. F , Paan,. E.. S.r(at~t. G . van )sen!. J L . and W~lkmu. M T M 1197Bl Uhrutruclvnl d~liennrrs a t m n comnathlc m a tncambatsble

11, 209-219. . -

C m n ~ M., C b p a l m i . F.. .rd Suhar, C. (19BO). Ultrauur~urd mvnupdon~ on L W - w pdlen utk#Iion uld &en tuk oaaniution after rll- .nd --pdlraaxn. 150. 211-217.

h v w . J.. .ad van Stden. J. (1979). CytDttnin in Lupku a l b u 111. Distiibutia, in hit.. w. m. 4J, 87-91.

-via. A. J. 6. (1957). Su-rhJ m the Faus L d ~ y h # h n y h am- putation. Nwr (*) 180. 612.

Daytan. D. F. (1971). Ovrrcomia( rlFiommpmibiUty in apple withkilled compstiblc pdkn. J A n Sr. Hnu. Sri. 99. 190-192.

IZ L Tour. G.. Jones, W. T.. ud Rou, M. D. (1978). Prcdoducuon d m t m p c i l c hybrids in &w aided by mdaprm t n n l p h u . N Z J I1 16. 61-68

dc Nettucarn, D. (1977). "lnsompwibility in An#inprms." S p ~ ~ r . V c r l q , &r. Un d New Y&.

dc N m ~ c a u n . D.. D e v m x . M., Boxhi. A.. Cmti , M.. Puing. E.. d SuT.tti. 0.. (1973.). V l t ~ ~ s ~ n l - ddl - incomp. t iUty mechanism in L p p . - uia. J cdt ~d 11. 403-419.

dc Nmumun, D.. h r e u x . M.. Lacri. Y.. P.cini, E.. Cmti . M.. ud W a n i , G (1971b). U I t m n r c l u d upem 01 uni1.ter.l intcnpecik incompatibility br w e n L p p r i n a pnuiu. d L ruuhan. Ca&ep. &pl s.3, 207-219.

dc N-n, D., ,A. M.. l a n d . U., Cnui. M.. P d n t , E.. d Su*tti , G. (1974). GaKoul ud u l t n a u a u n l .rpctl d -11. and c--in-ptibility io inanpifu h y b d b e e n dl-comptiblc L p . p ~ * t l whum and 4l.h- cofnpuib* L. 7 Tk.r. A#L CM. 44,278-288.

den Nus. A. P . M., u d Om. E. H. (1900). Effex or m w t a pollen on pollea pini ineonwic*l among lpria of C m i r L Euph* I#, 267-272.

Rumby. J. J . M. (1976). h d m protein w t h o b with polyoomen from unpdli- wed. EIOY. d dl-pollimmed Atmu wuim. Phu lDI, 29-33.

Dewen-. J. J. M. (1977). DiRmntimtd praan ~ t h w i r with p d m from h L wu*r bcfon kniliuh. Phu 193. TI-206.

Dkkhnn. fi. G. . d Lev*. D. (1973). C p c h e u d ud uhnrtnvurnl dis.-a bnram inrmpsdrv m p t i b k d insompuibk pllinuioru in R+wa. h. 1. st. Ur. Sn. 1) IU. 21-28.

Dim-. L. A. (19s) . A unnf fmr c- insanp.tiWiw k. nrr, aruh! .pain of tbe m w S.Luun. An RumJ $5, 122-423

-, C. J. (I#$). P- im cbmmmm runipduk. w. h. R. Sr. L.lr ar, 535-546.

mldiu. D.. Prp. 0.. -, G.. Yor.. C., LCiP, G., d HOrvAtb, G. (Imo). X-&m&-=? mmdu - by lJa: h*DI1. r(W. 01. CU.

~ r . L. Y. (19%)). w~ola-ee~ huonprib*-ddr- m i * p b U . h. NPI A d . Sn' U.S.A. I t . 166171.

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Eau&r. S. L.. ud Sturn, N W. ( I W ) Use of (lmrth -latin(( substsnrrr to a- inomp"bilitm in L i b A- Sr Henu Sn 51. 581

Emswekr. S. L , ud Uhrint. J . (1965). Intuulhon of tcmprnturr and sro*.th &or in owrotmine rK.imompatibility m Levn * I & l o m Thunb Hmdoux 52, 295-306.

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Evans. A. M.. m d hrud. T. (1955). GnTrin(l .nd hybridtvtion cipcnmmts in Ilr p u s 7- Nov. (-) 1% 607688.

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led&. G. (1978). Barky-whul hybrid:. IM& H&id P& E d , 15w Cmp EVCARM. W 1977, pp. 161-267.

Fr-. T E . ud W&, D. H. (1975). O e m u r u t i ~ ofBnr,us pollen md c x p n - lion d inmmptibiiity b mm E w P I , 757-765.

Fcmri. T. E.. ud W h . D. H. (1976). PoUcn prolela eynthesio and contml of insocapuibility in kuriu. I*n A#. Dn* 148. 243-219.

Punri, T. E.. d WJtce. D. H. (1977). hompatibility in &unn n i p n u in over- - by uutiny pdlca rirb qdohcximide. .EMUI 1%. 436-130. Pcmri. I. C.. Brunt, D., ud W h . D. H. (196la). Isolation of a plult @y.

c ~ p r a r i n invdvd with con& of i n t c d u l u -idon P&w ALyn.1 67, 270- "7, .,,.

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GUILIL, C. (1950). -# h.r*n IO voubil i ty due to styk knph. A- J. At 97. 2IP-224 - .. - . . - - - -- . .

G k . K. L. ( I N ) . Mrlvnbrm d& into plant pmcopbu, h "Plant W C u h v s is Crop hprwclosnt" (8. K. Sen and K. L. O h , d.), pp. 227-235. h u m . N a York.

G-I. J. E.. Pandry. K . K. , md Willums. E G (1980). Pdlon nuclei after ionisin8 imbation for a mnsfomation in NUN- N Z j Ibr 18. 339-341

G-h. R. J . Kdvuniemi. P J . , and Culwn. P. S (1981) Extending the nnsc of p l u t gmelic manipuluivn W- 31, 754-7S6

Gu-. R. P. (1978) A mt d tht n n m r pdlen lcrhn~quc m thc F n u r I-. 27, 825-890

H.dhy, H. H.. u d Opnsha*. S. J ( I M ) , lnrenpe~fir and Intevnrric hybndv ~ t h h "Hybridt~tion o f C q Plants" (W. R F ~ h r and H H. Hediry, edr). pp. 139-159. Am Joc A p n . md Cmp %I. Joc. Am. Mmdslan. Wisconrm

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Hcsht, A. ( I W ) G m n h of p l l a tubn of Onsrh -L t h m u e &ennee incomp.riblc srylea. Am J Bor 47, 32-96.

Hcshc, A.. (1%) Panid inactivation d incompatibility suhtmcr in thr s l i p a s and ntylw of O N h . h "Pollen P h y a o l o ~ ud Feniiiuuon'' (H. F. Linakeni, ed.), pp 237-243. Nonh.Hollmd Publ.. Amsterdam

Henny, R. J.. ud kshcr. P. D. (1973). Effect of auxin (3-mdolc acetic =id) on I. vim compatible u d incomp.tibk pdkn tube p o d m d n d e d ~tyles of Wtw h@mm Thunb, I w i b d t p Nrrul I. 14-17,

H v n m . M.. d Dickinxm. H G. (1979). Pollen-pinil incomptibiliry in hi. w. C h m p in the pistil following mmpatiblc and incompatibk intempxifir c r a r t . J C d / S 36, 1-18,

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H m . M . , d Dickinwn, H. G. (I*) Pdlen be pDnk Wowin# compatible ud i n m m ~ r i b l e intruffcific o d l i n u i m in AMu h W 141. 217-221.

H-HW&~, J. (1975&), lnrbnpuibility and a i m inlenctionr. Aarr. RN Pbl PLyrul. PC, 103-125.

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' J. ud Hcdapbrrbm. Y. (1975). Enzymic m o v d of p e n . H== dke mi- ppi l~c p m m u pollen tube m t v in the Cyophyl- Iruc. A n . ibr. (Mn) IN. 5.) 99, 163-165

wall oftbe M d r u o e . Am Em (kk) IN. 5.1 17.403-412. WdopHur i roa . J.. b. I. B . . , d HabpHuri ron . Y. (1974). Pdkn-w.P pre

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H n k p H u n a n . J. . H d o p H u r i w n . Y . m d 0arbrr.J. T (1975). Thc rrigm. rur. fur in incmp.ubility respnx" h. R S* L m k m , Sn B 189. 287-297

Hnbp*. Y. (1976). W i u t m dnmcmavdin A brndang Utes on the r lgma u h d p -in. M L r a 7. 83-36 .

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HnlapHamum. Y. . urd Shavanna. K. R. (1977). The mep~ivr turfarc of ~ h c an- polpm st,-. A n B.r (-) [N 5.1 41, 1233-1258

H i n u . K.. wd Nirkio. T. (1978) S&k sptcifirity ol stillma pmcebnn In Bruruo *mcr ud B -3. H W 41. 93-100

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Hovm. A. W (1962). Inanpaifir hykidiutwn bnrcen Tqblzun rrpl L. and T , lymmr Vw. and d y d s ol hybrid meiosis Cmp pSn 2. 251-214 Howktt. 0 . J.. Kmx. R. B.. Put0n.J. 0.. and HedopHarriwn. J . (1975) Pdlcn

w.U prcieinr: Pby*co-&mid cbuwtviutwn and mlr m nlf-incompatabiltty in C ~ w r h p t n v v Aor R. Su. Ladr. Sn 8 $38. 167-182

I b n b h . A M., and Coyne. D. P. (1975). Genetics d u i p a ,hap , coryledon p sition wd I l m r d o u r in w c i p d c- bewm F h d u v v l p n r L. m d Alu. Aorrimr (h.) wd irnpliutioru in bmding. J. Am. S* Honk. Srt 100,622- 626.

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Itlam. A. K. M. R., Shepherd, K. W., MI Spurow, D. H. B. (1976). Addition of Wivihul barley Ehrcnnol~mn to wheat. &r& W . Fw In: &r*y Clvl Sm#. 314 197.9, pp. 260-270. h, A. 8. (1964). A n m hybrid rmnbhlukn &wu& application of hormone d

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J-. S. A,, .6d -, R. I.. Jr. ( I W ) . M ~ i p l l n i a u d c d q m a ?+eenumbn arrcoar cmuirq h u h M w s . Shun specks. Linn 417,

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JoM. B hi., .ad Vuil. I. K (1961). Pbyidqn ofpollen. ibl Rm 97. 323-381 Jobri, B. M., h r i , D. C.. and Shiranm. K. R (1977). Pollen vi.biltty, aorngr

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bE3-604. I(&, W. A (1960). C+ o f T & S m n m L. polkn ~ b c r in compa~iblc md

inampatiblc a y k d a s i l e d pinik. T*n Ap)l Dnn $11, 351-354 Kmhll . W. A , , bnd h y h . N L. (1989). CRcnl d tempnrurc on prmdocorn.

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N.mliah. M E . and WUmr. D H (1967) lmn~unogrncr~cr ol.~ll.mcomp.t~bd~~y m B7aru4 dmn. L H d q r 22. 519-527

NunUah . M E., Barber. J I , m d Wdlacr. D H (19701 Scll~rncompatibiliry pmteinr in plants. Detmion, pnctics urd pasriblc mode of reloon Hnrdov 25, 23-27.

N d i n g . F A V . and Moms. D A (1979) Cylokinin level8 and cmbryu abonlon in ~ntcrspcit ic h l u cmrler Z rjlumph,rnol 91. 845-358

Nishm. T.. and H8n.t.. K (1977). Andy8k5 of S.spc~fic proletnr in m i p a of Btorrrro ehwm L, by i.oclmrir faeusi8ng H d a * $8. 391-396

Nirhaa, T . and Hmata. K. (1978) S-diclr spcciticlty of stigma protcxnn In Eramrm & a m and B mmp~tis Hmdirv 41, 93-100

Nlshio, I., m d Hmat.. K (1980) Rapid dctcrrion of S.gl!roprorcms olrelf.~ncorn. palibilr crvcifrn uaing e o n 4 reactson. Euphmca 29. 217-221,

Niruh, J P .(1952). Plurt hormones m rhe development of fruhls Q R,u Em1 17, 33-57

Nntzschr. W.. m d Hcnnir . L. (1976) Ovule culturr in g r a . ~ ~ . Z mnrmrwrh~ 77. 80-82

Ockmden. D J (1978). E n u t of hcxmc m d humtdity on self.inrompatibiltty in h r . rua b n Tksr Appl. Cnrr 52. 113-1 19.

P a n d y . K K. (1963) S l i p t i c lecmlon m d bud pallinalion in self. and cmsn-in compatible plants NuuwtrrrurAqlh 50, WE-tG¶

Pandry. K K (1964) Wemen18 ofrhc S.gene complcr I The SF1 dleien in N t r o l w ~ Cnn Re$. 2. 397-UXJ

P*, K K. (1975). % x d t m s f e r of aprrilc pncr vllhaut gamelrc (usion. Ndun ( L m h ) 256, 311-312

P a n d y , K K. (1976) The genus NLM"M Evolution of incompatibility in flowering plants. Lkn SM Spp Sn 7, 421-434.

Pandcy. K K (1977) Mentor pollen Pasibie role of wdl.held pollen gmwuh rub. sunces in ovcrcom~ng in ln - and intcr~specilir mncomprtibil~y Cmn8ra (Thr Hqw) 41. 219-229

Pmdey, K. K (1978). Gvnetic FM m ' f e c by mcann o l irradiated pollen. Coulua (m H y u ) +9, 13-69.

Psn*, K. K (1979). Ovcr r~ming incompatibility and promoting genetic nccm. bsnation in h e r i n g plmt.. N.Z J Bol 17, 645-663.

P W . K. K (1980), Further rv idmcc for egg tran#formarbn in NI(OIUM Hrfdsly 41. 15-29.

Pcbquin. S . J (1981) C h m m m d and rytophmic manipulations Phnl Brnd 2 /Tu/ P m Pbnt Bred S p / Zd 1979. pp. 117-1 $0.

Phillip. C! C . , CoUms. G . &?a& ~ i y b r . W L. (1982) ln t rnpmf i t hybndiution of rrd clwer ( m y d i m purmr L. ) with T m r i m w H w l . using ia utlm embryo -. Tlrn -1. Cnn $2. 17-24.

*ring. I. A. (1979). Funlnr i n m r i p l i m s on pan id incornprribilily in c m b e r m H& r & m L. and W. W $ m . h "Broadening Generic Buc d

ANOlOtPUU INCOYPATUIUIY AND CROP IMPROVKMLNT 107

C m p " (A C Z-cn and A M van Hancn. n l s ), pp $10-315 C r n w (or A c ~ v l t v r d Publuhnng and b c u m c n t a t m . Wagmnngm

PYLIMI. R A 119801 Atcem~ts 10 m m m r mn1.l ,nrorno.!!bt,llr bclnrn Ho,. Ila "& L 'and k but& L E m i9. 369-377

. . Panyl l i . G. W.. and Stavcly. J . R. (1975). Binct hybndnratton ol Mconm npld.

x N v l u r m J Hod 66. 281-284 Power, J B . Cummms, S E . and Cakiag, F. C (1970) Furlon ofirulsrrd plan,

pmtapluts N.rm (Ldn) 225, 1016-1018 R e v a n . V (1977) Applied u p e t s d cmbrjo sulturc b "Applied and Fund..

mcntd Alpcts of PLnt CLU. T ~ u u r .nd O a m Culrun" 0 Rcincn and Y P S. Baj.1. eds.), pp. 375-397. S p r i ~ v V r d a g . &rlm and New York.

Runulu. K. S.. Brrdcmeijcr. 0. M . M.. Dijkhu81. P.. do Nettancoun. D.. and Srh l b i b . H. (1979). Mentor pollen &a on w n o p h y t i c inmmpt,bilbty ~n Nuo. bru, ONOk. and Lp.pnnnn TLn Appl Gemti 54. 215-218

Ren&uwuny. N S (1963) Conlml of fenilkation and embryo dcvclopmcnt I n "Rc. m t Mvure. m the EmbrydogyolAtqioapnns" (P M l h c . h w m , cd.), pp 327- 153. lat k. Plant Morpbol . Univentty of Dclhi. Delhl

Rangasratmy. N. S (1977). Applications d m our. poUma!ioh and on u r n Lnillzation h "Applied and Fundamcnul Aspetr of Plan! Cell, Tissur mnd 0 q . n Culture" U. Retncn and Y P S. Bajaj, eds.), pp. 112-425. Springer.Vcrl.g. Berlin and New York.

Rmd. S. M., and CoUinr. C . B. (1978). lncenpcific hybnds in Ntrolma through m run culrum ofienlliKd d n . J H m d 69. 311-315.

R m , H.. Ralcy. R.. Bmse , E. L., .nd L v . C . N. ed,. (1981). The manipuiation ofgemtac systems in p h t b d i n g . PWor Tmu R br. Lndon, Sn B 292, W1- 609

Ricy, R.. C b p m m . V.. andJohnurn. R. (1868) The incarporation ofahen dilca.c mutance in wheat by -tic in le t fmce with the replation of melet$c chm m-me sp.p%i$ Cnul. Ru IP, 199-119.

Rily . R . b w . C. N., and Chaptiua. V. (1981). T h e control of recombination. ah', T- R br. Mol, Sn B ZW. 529-531

Rmbbela, G. (1960). Vber die tnuuryunvenragliehkeit venshiedcnsr Brmsa-Ar. ten 4s einca gehemmtm Pd*nrN.uchwachrumr Z y c k SO, >M)-312.

Robens, I. N., Lead, A. D., 0ckmd.n. D J . , m d Dirbnmn, H 0 . (1979). A lfyctlprotetn u u x h t d with the .cqui.ition of self-incompatibiltry aynem by m c turing uigmu of Bwr- .h- Flmu 146, 179-183.

Robens. I. N.. Stead. A. D . Ckkcndon. I) J . , and Dtckinron. H. G. (1980) Pollen ai@'ru inlenstion8 in B n u k . drrrr. Ilar. Appl Cnrt 58, 241-26.

R-, H. P. (1975). S l i p a p p l i u t i o n dm er t ru t from r a p pdlen (Bm,u# wpw L. ) disco rlf-incmparibility in B w e h sprout (Brurua rhwu var "gemmi- ten"), lmmquibilip N m l 6. 80-84.

R-n. H. P., andvan DiJk, A. J . (-72) Brrakin~ineornpa~ibility in BraruadlWI. L, by s10e1-bmsb pol l inah. EllCIpn 01, 48-$1.

R o g m , H. P., van h j k , A. J., d Dorrnan, C . (1972) Electric aided pollin.. lion: A mabod of b d i l incompuibiiity in &astir, Phrrta L. EUpnylue 21, 181- 1M.

L a d d . W. G.. d M e r . P. D. (1975). Ulens of high t m p n t v n crrumrnts .Id red yield and dl-incornpuibility in C b y m I h u m Erphrua 24. 317-322.

Surhinu. M. ( I W ) . Studin m ~&br tn td in l f .n iMJly synthmiud np(&uriu w). 1. P, hybrids bet- B r.rqnnir p p and B *nus v o u p end chr de. rivad P, @mu. J#a J &rd 14. 126-217.

Snn'. D. C (1981). Somc u p e t r ddf-inmrnptibiit ty in AN.u k j M . P h l Md b l Nnv* 2. 110-111.

S u t n , D. C., ud Mat. J . P. (I98l). Efiwts of gmwth regulatan on ~neomptablr c m m in rhc p u l u l A n r * r L . J 4. Bot 13, 1293-1101

Surri. D. C.. u d Shivann.. K R (1976.) Attempts to ovcrromc intenpifir ,n. wrnptibdity in -rn using m q ~ a r i o n pallen Ann Bo1 (Leden) IN. 5 1 41. 891-1193.

Sutri. D. C . and Shavuula. K R (19766) Rccopi~ton pollen d ten mcompuibilily in Fmmu 1 ~ ' b i I a g N w ~ l . 7. 22-24.

b t r i . D. C.. d Shivurn. K. R. (1978). Srrd ut foilowing eompeibb pdlinanan an in-plibly poll~rntd flown of h m u 1inn)wnbdte N w ~ 1 . 9. 91-93.

Sutri. D. C.. d S h ~ v w . K. R. (1979). Role olpdicn wall proteins in intnrper~fir incomptibiliw in S.rr*rpn *ry.lnrr P h # m q k o l o ~ 29, S2CSSO.

h r i . D C , d Shtvann.. K. R. (1Wa). Uectropheret~c pttems ofpmtcin~ and iarvmct in dmlapina pisti* sf k r A J M Immmpihhg Nmrl 11. 24-29.

Sutri, D. C.. ud S b i v . ~ . . K. R. ( I W b ) . LlRucy ofmentor pallen tn ovarcorntnp i n t r u p i l k incompuibiiity in h u , R h u and Bmr-. J C M Cnn 15. 101-112.

Sutn . D C., Ndini. M. S.. u d M m , J. P. (1981), Tirlue cultvm and p m p c t r of crop impmvemrnl m Anr lu h @ p and other 0 3 4 s crop. h "Tiuur Culture dEconomiully I m p n m c % w i n Dewlop~ng Cmntnem" (A. N. Rul, d . ) , pp. 42-57. Natiaul Univcnaty of Sinppcre. Sbngapam.

Suui . D. C.. Mou. J. P.. and Ndini, M. S. (1982). Thc uu of i . nho mrthcdr in pauKLnut improvement. h "PIMI Cell Culture in Cmp Impmemcnl" (S. K. Sen md K. L. Gila, d.), pp. %5-370 Plenum. Ncw Yo*.

Saritri. K. S . Gansp.rhy. P S., .ad Sinha, S. K. (1980) Scnritirity lo I m tem. p n r v r e in pd*n -ation ud fruit m in C k a v t i r L. J. Ezp &r. 31. 47W81.

Sc)uedcr. 0.. u d Vuil. I. K. (1980). Pmoplul fusion and .omcis hybridgution. 1.r Rm. C j d , +. l1.,21-46.

Sddry, M. (1974). Ancmncnt d mdo&A Icchniqum fa S-Jlcle idcntnhution in aini. k. E- 13, 543-551.

Shum.. D R . Cbowdhuq. J 8.. Ahuja. U., and DM;h.r, 8 . S (1980). B t c r rpcific hybridization in Fnus Solam A r r m b n m n S and S. k h . lam thrwgh c m b ~ cdmre. Z & ~ n n w h t 85, 248-253.

Shimobu. I.. and S.Lmoto. 5. (1061). Interwncnc h y b n d h w n betran A p c d & h , rad Hmhrn buhmm J p . J Cnn 56. 505-515.

Shiv-. K R.. .nd R.nwvamy, N. S. (1469). Ovc-in( rlCinmmptibility in Pm& rdllrir. 1. W y d pdinmrwa, poUirurbn with stored poUm, and bud fl&. fimm@dqr 19. S71-380.

Shiv-. K. R.. u d %mi. D, C. (1061). S u p . lurlue n l c w activity and r i p . rrrrpiviw in amme wu a by m sip. A*m Bot ((Mm) IN. S.1 47. 5 1 4 . -. , - - - . .

Shiv-.. K. R., HsbpHawiwn. Y . . d HnbpH-. J. (1978). The pallon p i p intendon: Bud pdbuim in I~G C r v i k n e , AN. &r. N n l . 21,107-1 19.

shiv^, K. R:. Jdui. B. M., and Sulri. D. C. (1979). "Rvelopmmt and P h y b k ~ d- P k . " Todsv uld Tomormr P h a n uld Publ*knr. N w D&. - '

A. K., guri. D. C., d Mor.J. P. ( I W ) . Vtilivtia o l d A r y k speck U ICIIIIUT. k. h. Ondr W w (11. W. Oibbocu, d.), pp. 62-90 ICRISAT. r

ANDIOYKRY INCOMPATIBlLITY AND CROP lMPROVLMLM 109

l p n n or& FYX p u n und& arptbr mndmona 2 q t n m p h ~ r a s l 91. 95-103 Snapc, J W . &nnctl. M D . and Stmpson. E (19801 Prnl pollnnal~on trrnlr ~n

c m u c t of hrxaplosd wheat n t h trtrapload Herdrun bulhrum Z ~ ~ I Z - H ~ I 8 ) . 200-?M

Sulkcr. H T (1980) Utilksalton 01 wild lpcicr lor crop mmpmvcmrnt A I A p * 31. 111-147

Srmlcy. R G . m d Linskcnr. H P (1974) "Pollcn. B Io Io~ . B ~ w h ~ m w t r y and M m . ~ m m l " Sprin~r-Vcr lag. Brrlrn and Nc* York

S t c d . A D . Robsns. A D. . m d D~ck~nson. H C (1979) Pollcn pntll tntenctmn in EN& Jnum, wenu prior lo pdlcn Fnnanatton Ph-m 146. 211-216

Sled. A. D . . Robens. A D . and Dickmwn. H G (1980 ) Pollen-.lip. Inter. v t i m in Brurw .Inem The mlr of a t p a t i c pmlcint rn pollen pram dhesion J G U h 41. 417-423

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Stndcr. R . F . u rd Gunet. R . P. (1976) The mentor pollen phenomenon m black cottonwmd. Cm J &I 54. 820-830

Stecdcr. R. F . Katcr. R.. m d Strrnarkm. V (1980) IntcnpcriRr cmrubibty stud- tes in poplrn Them Appl CIVl 58, 273-202

Stevut. J M (1981) In vzm k n i l i u ~ i o n m d embryo n c u c . Enr~snn G p &I 11, 301-105.

Scnnn, J M . m d Hsu, C L. (1978) Hybridiution oldtplaid and tetrapioid cottons &mush m.@#ub cmbyc culturr. J H d 69. 101-408.

Scnub. J. (1916) Zur En~wicUunpphyid+c det Sclbaserilttar von Pdmu Z No. u@A 1, 287-291

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Stnub. J (19%) Du ukrv indcn drr Wkrcr i l l l .~ Z &I 46. 98-1 11 S u b m h m y a m . N C (1979). Haploxdy h m Hwdnnn ~ntcrspeific e m . P u l 2

Dihrpleidid. from H ud H I p u t u * )"kn ApY Gew 55, 139- I*.

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S r u n i m t h m . M 5. (1955) Overcoming emu.incompa~ibiIity amen8 m e Mcr,rm &+id .pccier of Shun N.IY~ (WOI) 176, 23-26.

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T.L.huhi, H. (1973). C m n i c ad p h y d d q i u l uldysia dpseud~IJf.caepstibility io hi b ~ . . jp j GM 48,n-33

Tulhiu . M., Kate, M., urd I d r o w . S. (1980). Appl iwion o l a v l c d t v r r w p&nim d i n t e m c r i c a i n t m p d t k hybrids i n Bmrua md R+ru Jpr J. Clu. 55. 171-317.

T a w , I . B.. ad Al-Kummcr. M. K. (112). The &-tion of snnp*. h w

innder. n*r Aptl CM 61. 59-64 T a $ x & % . R. P.. a d kdemn. M. K. (15'80). Mnhcda d a d c

iarrnpcitkbur*nin rahlia E+Z¶. W I 4 M

incompatibility significance in crop improvement

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