A STUDY OF STERILOIB CHARACTERS IN A MONOTELOSOMIC LINE OF CULTIVATED OATS,

AVENA SATIVA

M. T. C. CHOW Departmenr (g7Phpro1ogy, Lullal University, Quebec, QuPbec

Three telosomic lines ST-20" of cultivated uats, Avenu saril'u L. , were studied for their different expression of spikelet characters. An A srerilis type of spikelet was observed in one monotelosomic line in contrast to the A. sarivu type (exception for one reduced twisted geniculate awn on the primary floret only) present in its monosomic counterpart. The genes responsible for cultivated vs. wild type spikelet characters were located on the short arm of ST-20. and the expression of the wild characters was found to be influenced by other suppressors located on chromosome(s) other than ST-20. It seems that the suppression of wild types of spikelet characters in cultivated oats is governed by Inore than one gene complex located on different chromosomes.

Trois lignkes tilosomiques your le chromosome ST-20' de I'avoine cultivee, Avena sativc~ L. , one ete ttudiPes parce qu'elles avaient des caractiaistiques diffkrentes de l'ipillet. Une lignCe monotelosomique prdsentait un CpiBBet de type ster-ilis tandis que sa contrepartie monosomique ne prksentait qu'une barbe rkduite, coudee et tordue sur le grain primaire seulement. Ees gknes responsables du type cultive vs steriloi'de des caractkres de 1'Cpillet ont Cte localisks sur Be bras court du chromosonle ST-20 et l'expression des caractCristiyues non cultivees est influencke par des suppresseurs localisds sur des chromosomes autres que ST-20. I1 semble que la suppression des caract6ristiqiaes non cultivkes est gouvetnee par plus d'un complexe ginique Bocalisk sur differents chromosomes.

Introduction The fatuoid phenotype is characterized by having a twisted geniculate awn. an oval

disarticulation surface (sucker mouth) and basal hairs on each grain of the spikelet. These characters seem to be inherited as a unit and are often referred to as the "fifatuoid complex". The genetics and cytology of fatuoids in cultivated oats have been widely studied; a detailed review was made by Huskins (1946). It is generally agreed that fatuoid suppressor genes are responsible for the cultivated type of expression rather than allelic alternatives of normal vs. fatuoid genes (Coffman and Mac Key, 1959). Fatuoid suppressors seem to be closely linked in a sequence of I (awn suppressor), C (resulting in fracture and epistatic to abscission), H (hair suppressor) and B , (promoting basifracture, inhibiting disarticulation and modifying abscission) (Coffman and Mac Key, 8959).

The steriloid phenotype differs from the fatuoid in floret separation but it is similar in spikelet separation. While the primary floret of either phenotype is separated from the peduncle by an oval disarticulation, the upper florets of the former are solidly attached to the rachilla so that the spikelet dehisces as a unit. The steriloid characters are controlled by a gene or gene complex designated S by Florell (8 93 1 ) and renamed Be by

'Contribution from the Department of Phytolopy, Lava1 University and contribution No. 73 from the Research Station, Agriculture Canada, Ste-Foy , Quebec. Manuscript received April 12, 1976. Can. J. Genet. Cytol. 18: 525-528,1976.

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526 M . T. C. CHOW ET AL.

Coffman and Mac Key (1959). In the presence of gene B,, the plant with a genotype of ""i 6"z b1" exhibits the sberilis type of sgikelet characters. The B,-gene regulates basifracture of the upper florets but does not have a modifying effect on spikelet separation.

The htuoid suppressor genes of cultivated oats, A. sotiva, were located on chromosomes 1 3 (Nishiy ama, 1 933; Hacker and Riley, 1965; Gauthier, 1 967; Singh and Wallace, 1967), and 14 (Sun, 1965) sf the submedian group. The short arm of the subterminal chromosoirae 19 carries a weak suppressor of the fatuoid expression (Sun, 1965). In addition, Thomas and Mytton (1970) located a fatuoid suppressor gene on the long arm of a submedian chromosome and a gene controlling regular synapsis on the short arm of the same chromosome. However, the gene location in respect to steriloid characters has not been reported in A. sutiva.

The object of this research was to study a sterilis type of spikelet found in a monotelosomic line of A. snrivcm and to associate genes for normal expression to a specific arm of a c hrornossme.

Materials and Methods The source and origin of the lines used in the study are presented in Table 1. Ditelosomic line

R-741 and rnonotelosomic line 16-748 were isolated from the selfed progeny of the monosomic lines R-741 and R-748 respectively. The line D-412 was identified as ditelosomic ST-20'. by Dubuc and McGinnis (1970). Telosomic lines R-741 and R-748 were identified as telosomic for the same arm as line D-412 by interline crosses and meiotic studies of the F, hybrids (Chow, 1976).

TABLE I

List of aneuploid lines

Chromosome Line constitution Variety and origin Authority

D-4/2 40 + 28 Sun II (spontaneous) Dubuc and McGinnis (I 970) R-74 I 4 1 , 4 0 + 28 Garrp (300 r)* Andrews and McGinnis (1964) R-748 4 1 , 4 0 + t Rodney (I 50 r)* Andrew and McGinnis (I 964)

jp06

*X-ray dose.

Results and Discussion Monotelosomic line R-748 and ditelosomic lines R-74 1 and D-412 were telosomic

for the same chromosome arm, namely ST-20ge Monotelosomic line R-748 exhibited distinct spikelet characters. The primary grain

separated from the peduncle by an articulation having a 'bucker mouth" whereas the upper grains remained fully attached. A twisted geniculate awn and profuse basal hairs appeared on each grain of the spikelet (Fig. 1). This characteristic resembled that ofA. sterikis except that the Batter has generally no awn and basal hairs on florets above the secondary. However, plants of monosomic line R-748 showed one reduced twisted geniculate awn on the primary floret only. Spikelet separation occurred by fracture with the callus scar obscure or not evident. In contrast, ditelo 8-741. ditelo D-412 and monosomic R-74 1 produced even a weaker awn only on the primary floret. Therefore a gene complex responsible for the cultivated type of spikelet characters is located on the short arm of chromosome ST-20. It is assumed that this gene complex is a set of fatuoid suppressor genes, i c h b,. In the absence of these genes, the plant would express the

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STERlLOlD CHARACTERS IN OATS

Fig. I . Steriloid expression with the primary grain (a) having a sucker mouth and secondary and tertiary grains (b, c ) remaining fully attached.

sterilis type of spikelet characters since the B2-gene, which is independently inherited, regulates basifracture of the upper florets (Coff~nan and Mac Key, 1959).

Other fatuoid suppressor genes were located on chromosomes 13 (Nishiyama, 1933; Hacker and Riley, 1965; Gauthier, 1967; Singh and Wallace, 1967) and 14 (Sun, 1965). Thomas and Mytton (1970) located a fatuoid suppressor on the long arm of a submedian chromosome. The polymorphism in steriloid expression found in telesomic lines W-748, Fa-741 and D-412 would be brought about by the influence of other suppressors probably located on chromosome(s) other than ST-20, such as 13 and/or 14. This is similar to Sun's observations (1965) that a small deletican of the short arm of chromoso~ne ST-19 resulted in the true fatuoid expression in ~nonosomic SM-14. This monosomic SM- 14 would have otherwise exhibited an intermediate fatuoid expression. Then he concluded that the small deletion of the short arm of ST- 19 might also carry a gene or genes for fatuoid suppression. Considering their karyotypic similarities, it is suggested that chromosomes ST- I9 and ST-20 are actually the same chromosome.

It seems obvious that in cultivated oats, the suppression of wild types of spikelet characters is governed by inore than one gene complex located on different chromosomes. Yet, the mode of gene interaction still remains to be clarified.

Acknowledgments Financial support from the Quebec Agriculture Research Council is gratefully

as knowledged .

References Chow, M. T. C . 1976. The identification of several aneuploid lines and reciprocal translocations and a

study of steriloid expression in cultivated oats, Awns sarirrr L . Ph.B. Thesis, Lava1 University, Quebec, Quebec.

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Dubuc, J . P. and McGinnis, R. C . 1970. The identification and meiotic behaviour of a ditclosomic line in Avena scrti\vcl L . Can. J . Genet. Cytol. 12: 876-88 l .

Florell, V. H. 193 1 . Inheritance of type of floret separation and other characters in interspecific crosses in oats. 9. Agr. Wes. 43: 365-386.

Gauthier, F. M. 1967. The identification of monosomic lines sfA11ena scrtfvm E. and their associatiolm with distinct markers. Ph.B. Thesis, University of Manitoba, Winnipeg, Manitoba.

Hacker, J. B. and Riley. R . 1965. Morphological and cytological effects of chromosome deficiency in Aventr stativn. Cars. J . Genet. Cytol. 7: 304-3 15.

Huskins, C . L. 1946. Fatuoid, spelaoid and related mutations ofoats and wheat. Bot. Rev. 12: 457-514. Nishiyama, I. 1'333. The genetics and cytology of certain cereals; IV. Further st~ldics on fatuoid oats. Jpn.

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Thesis, University of Manitoba, Winnipeg, Manitoba. Thomas, H. and Myaton, J . 1970. Monosomic analysis of fatuoids in cultivated oat Avcn6z safivct. Can. J.

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