INTRODUCTION

Colocasia Schott, a small genus of familyAraceae, comprising about 13 species, is widelydistributed in tropical and subtropical Asia(MAYO et al. 1997). 11 species are currently rec-ognized in China (LI 1986; LI and LONG 1999;LONG and LI 2000; LONG and LIU 2001). Somespecies, such as C. esculenta, are widely cultivatedin tropical, subtropical and temperate area as animportant food crop.

Since NAKAJIMA (1936) did the chromosomestudy on Colocasia esculenta, abundant cytologicaldata were reported for Colocasia (KURAKUBO

1940; ITO 1942; RAO 1947; DELAY 1951; SHARMA

and DAS 1954; MOOKERJEA 1955; PFITZER 1957;FUKUSHIMA et al. 1962; YEN and WHEELER 1968;BAI et al. 1971; KAWAHARA 1978; KURUVILLA et al.1981; COASTES et al. 1988; OKADA and HAMBALI

1989; PETERSEN 1989; SREEKUMARI and MATHEW,1991a, b; KOKUBUGATA and KONISHI 1999), but

cytological data are mainly associated with differ-ent populations of C. esculenta for its variation ofchromosome numbers. Although most species ofColocasia are distributed in China, and 4 newspecies, C. heterchroma, C. gaoligongensis, C.gongii and C. lihengiae, were recently describedfrom Yunnan Province, China (LI and WEI 1993;LI and LONG 1999; LONG and LI 2000; LONG

and LIU 2001), there was no cytological study onthese species up to the present time.

This paper deals with karyomorphologicalaspects of 3 species in Colocasia from YunnanProvince, China. Of them, C. gongii and C.gaoligongensis were recently described (LI andLONG 1999; LONG and LI 2000).

MATERIAL AND METHODS

The materials for cytological analysis were intro-duced from following sites and cultivated in KunmingBotanical Garden. Voucher specimens were depositedat the herbarium of Kunming Institute of Botany, Chi-nese Academy of Sciences (KUN).

CARYOLOGIA Vol. 56, no. 3: 323-327, 2003

A Cytological Study on three Species of Colocasia(Araceae) from YunnanZHIYUN YANG, TINGSHUANG YI, HENG LI and XUN GONG*Kunming Institute of Botany, Chinese Academy of Sciences, Kunming Yunnan 650204, China.

Abstract - Chromosome numbers and karyotypes of three Colocasiaspecies from Yunnan were reported. Their karyotypes were as follows:2n=2x=28=22m(1sat)+6sm for C. gongii ; 2n=2x=28=20m+8sm forC. gaoligongensis; 2n=2x=28=20m+8sm for C. gigantea. Common kary-omorphological characteristics of three species examined were: (1) the sim-ple chromocenter type of the resting chromosomes and the proximal type ofthe mitotic prophase chromosomes; (2) the chromosome number 2n=28 and(3) the chromosome complement of m- and sm-chromosomes. x=14 wasconfirmed as the basic chromosome number of Colocasia. There were dif-ferences among species in the number of m- and sm-chromosomes as well assatellite.

Key words: C. gongii; C. gaologongensis; C. gigantea; basic chromosome number;karyomorphology.

* Corresponding author: fax +86 0871 5150227; e-mail:gongxun@mail.kib.ac.cn

C. gaoligongensis: Hills at south end of Tenghongvalley, Tengchong county, Yunnan, SW China, 3700ma. s. l. Yi Tingshuang 02012. C. gongii: Kagang, Jiemaoin Yingjiang county, Yunnan, SW China, 760m a. s. l.,Long Chun-lin 9826. C. gigantea: Pingbian county,Yunnan, SW China. Yi Tingshuang 02013.

For the observations of somatic chromosomes, thegrowing root tips were pretreated in 0.1% colchicinesolution at room temperature for 2.5 hours, and werethen fixed in acetic alcohol (3:1=absolute ethanol andglacial acetic) at 4°C for 30 minutes. They were mac-erated in 1:1 mixture of 1 mol/L hydrochloric acid and45% acetic acid at 60°C for 4 to 5 minutes and thenwere stained and squashed in 1% aceto-orcein solu-tion before observation.

Karyomorphological observations were made onchromosomes at resting stage and mitotic prophaseand metaphase, and their classifications followedTANAKA (1971, 1977). Karyotype formulas werederived on measurements of metaphase chromosomesfrom photomicrographs. The nomenclature used todescribe the karyotype followed LEVAN et al. (1964).The classification of karyotype asymmetry followedSTEBBINS (1971).

RESULTS

The chromosomes at resting stage and mitot-ic prophase and metaphase of the three speciesexamined are shown in Fig. 1. Their chromo-some number is 2n=28. The karyomorphologicalcharacteristics are summarized in Table 1.

In the nuclei at resting stage, several darklystained heteropycnotic bodies, which were irreg-ularly protruded, were clearly observed. The oth-

er region was just very dilutely stained, so theboundary of the bodies was rather distinct(Fig. 1A). Karyomorphology of the nuclei at rest-ing stage was categorized to be simple chromo-centre type.

In the mitotic prophase chromosomes, hetero-and euchromatic segments were distinguishable,and heterochromatic segments were mainly dis-tributed in the proximal regions (Fig. 1B). Themorphology of mitotic-prophase chromosomeswas categorized to be the proximal type.

The chromosome length of C. gongii rangedfrom 3.49 to 1.67 µm (Fig. 1D). The total lengthof chromosomes at metaphase was 78.91 µm. Thechromosome complement metaphase consistedof 22 metacentrics (m) and 6 submetacentrics(sm) chromosomes, and a satellite was observedon the short arm of one chromosome of the 13thpair of 13. Karyotype asymmetry was estimated asStebbins’ 1A-type.

The chromosome length of C. gaoligongensisranged from 3.60 to 2.23 µm (Fig. 1E). The totallength of chromosomes at metaphase was 80.80µm. The chromosome complement at metaphaseconsisted of 20 m- and 8 sm-chromosomes. Kary-otype asymmetry was estimated as Stebbins’ 1A-type.

The chromosome number of C. giganteaagreed with the previous reports (KURAKUBO

1940; ITO 1942; HOTTA 1971; RAMACHANDRAN

1978; OKADA et al. 1989). The chromosomesranged in length from 3.65-1.96 µm (Fig. 1C).The total length of chromosomes at metaphasewas 80.68 µm. The chromosome complement at

324 YANG, YI, LI and GONG

Table 1 – Measurements of somatic chromosome at metaphase in the representative karyotypes in C. gongii, C. gaoligongen-sis and C. gigantea.

C. gongii C. gaoligongensis C. giganteaK=2n=2x=28=22m(1sat)+6sm K=2n=2x=28=20m+8sm K=2n=2x=28=20m+8sm

Chrom. RL AR PC RL AR PC RL AR PC1 4.42 1.16 m 4.45 1.10 m 4.34 1.09 m2 4.25 1.28 m 4.25 1.05 m 4.11 1.81 sm3 4.13 1.12 m 4.17 1.13 m 4.00 1.13 m4 4.02 1.14 m 4.09 1.20 m 3.95 1.14 m5 3.95 1.09 m 4.05 1.88 sm 3.86 1.17 m6 3.81 1.09 m 4.02 1.10 m 3.81 1.10 m7 3.72 1.24 m 3.70 1.30 m 3.78 1.10 m8 3.65 2.07 sm 3.42 1.08 m 3.67 1.09 m9 3.43 1.28 m 3.27 1.51 m 3.57 1.20 m10 3.36 1.04 m 3.24 1.21 m 3.54 1.10 m*11 3.14 1.92 sm 3.15 1.80 sm 3.46 1.36 m12 3.04 1.31 m 3.03 1.80 sm 3.05 1.82 sm13 2.49 1.20 m* 2.69 1.31 m 2.50 2.94 sm14 2.61 2.12 sm 2.51 1.85 sm 2.39 2.20 sm

RL: relative length; AR: arm ratio; PC: position of centromere; * satellite-chromosomes.

CYTOLOGICAL STUDY ON COLOCASIA FROM YUNNAN 325

Fig. 1 – The resting nuclear, prophase and somatic metaphase chromosome of three species in Colocasia. a) Resting nuclearof C. gongii; b) Prophase of C. gongii; metaphase plates and karyotypes respectively of C. gigantea (c and C), C. gongii (d andD) and C. gaoligongensis (e and E).

a

b

c

d e

E

D

C

metaphase consisted of 20 m- and 8 sm-chromo-somes. Karyotype asymmetry was estimated asStebbins’ 1A-type.

DISCUSSION

Previous cytological studies on Colocasia indi-cated some confusion concerning the basic chro-mosome number of the genus, and some differentchromosome numbers were estimated, such as2n=28,36 and 42, and x=7, 12 and 14 were sug-gested as the basic chromosome number of Colo-casia by some previous researchers (RAO 1947;DELY 1951; DARLINGTON et al. 1955; MARCHANT

1971; RAMACHANDRAN 1978; COATES et al. 1988;OKADA et al. 1989). But, wild Calocasia species,except C. antiquorum, possess the same chromo-some number, 2n=28. According to chromosomebehaviours in meiosis (VIJAYA et al. 1971; OKADA

et al. 1989), the basic chromosome number ofColocasia is x=14. The populations of C. esculen-ta with 42 chromosomes are triploid, 3x=42. Thefact that plants with 42 chromosomes are sterileis one of evidences. x=12 was suggested as a basicchromosome number of Colocasia based on theobservations of RAO (1947) and DELY (1951).However, none of the more recent studies onColocasia have confirmed x=12 as a base number.It therefore seems that the plants observed witha base number of 12 were either misidentified asColocasia species, or that the chromosome countswere inaccurate. Three species studied in thispaper are diploid with 2n=2x=28. C. esculenta isthe only species in Colocasia with various chro-mosome number and various basic chromosomenumber. The populations with chromosomenumber of 2n=42 were triploid with a basic chro-mosome number of x=14 but were not hexaploidwith a basic chromosome number of x=7. Thechromosome number of populations cultivated ofC. esculenta may vary due to long history and thevarious conditions of cultivation.

The karyomorphological characters of threespecies studied here were almost the same to eachother, such as the chromosome complements onlyconsisting of m- and sm-type of chromosomes, kary-otype asymmetry of 1A-type. But, there are differ-ences in the numbers of m- and sm-chromosomes aswell as satellite-chromosomes among species.

C. gongii is different from C. gigantea by tubi-form convolute and golden yellow spathe bladewhich usually gapes at anthesis. C. gaoligongensis

is different from C. esculenta by the widely obovateblade and spadix without appendix. In our study,the chromosome complement of C. gongii was dif-ferent from that of C. gigantea by the number ofm- and sm-chromosomes as well as satellite. Theformer possessed 22 m- and 6 sm-chromosomes,and lower asymmetry’s index with 1.36. The latterpossessed 20 m- and 8 sm-chromosome?mandhigher asymmetry’s index of 1.45. C. esculentashowed diversity not only in the chromosomenumber but also in karyotypes. Five karyotypesin C. esculenta were reported (SREEKUMARI andMATHEW 1991). So, karyotypes cannot be com-pared between C. gaoligongensis and C. esculenta.

It is very necessary to study China’s otherspecies in Colocasia for revealing phylogeneticrelationships of whole genus.

REFERENCES

BAI V.K., MAGOON, M.L. and KRISHNAN R., 1971 –Meiosis and pollen mitosis in diploid and triploidColocasia Antiquorum Schott. Genetica, 42: 187-198.

COATES D.J., YEN D.E. and GAFFEY P.M., 1988 –Chromosome variation in Taro, Colocasia escu-lenta: Implications for origin I the pacific. Cytolo-gia, 53, 551-560.

DARLINGTON C.D. and WYLIE A.P., 1955 – Chro-mosome Atlas of Flowering Plants. George Allenand Unwin Ltd., London.

DELAY J., 1951 – Nombres chromosomiques chez lesphanéorgames. Rev. Cytol. Biol. Végétales, 12:1-368.

FUKUSHIMA E., IWASA S., TOKUMASU S. and IWA-MASA M., 1962 – Chromosome numbers of thetaro varieties cultivated in Japan. ChromosomeInformation Service, 3: 38-39.

HOTTA M., 1971 – Study of the Family Araceae.Men. Coll. Sci. Univ. Kyoto, series B: 76-95.

ITO T., 1942 – Chromosomen und Sexualität von derAraceae I. Somatische Chromosomenzahleneiniger Arten. Cytologia, 12: 313-325

KAWAHARA T., 1978 – Chromosome number of Tarosin Nepal and India. Chromosome InformationServices, 24: 4-5.

KRISHNAN R. and MAGOON M.L., 1977 – Ediblearoids-new insights into phylogeny. In: C.L.A.LeaLiuy (Ed.), Proc. 3rd Int. Symp. Trop. RootCrops, pp. 58-60. Int. Inst. Tropical Agric.,Ibadan, Nigeria.

KURAKUBO Y., 1940 – Über die chromosomenzahlenvon Araceae-Arten. Bot. and Zool. (Tokyo), 8:1492.

326 YANG, YI, LI and GONG

KURUVILLA K.M. and SINGH A., 1981 – Karyotypicand electrophoretic studies on taro and its origin.Euphytica, 30: 405-413.

LEVAN A., FREDGA K. and SANDBERG A.A., 1964 –Nomenclature for centrometric position on Chro-mosome. Hereditas, 52: 201-220.

LI H., 1986 – The ecological phytogeography andorigin of the Araceae. Acta Botanica Yunnanica,8: 363-381.

LI H. and LONG C.L., 1998 – A Preliminary Revi-sion of Araceae in China. Acta Botanica Yun-nanica, Suppl. X: 12-23.

–, 1999 – A new species of Colocasia (Aracea) fromMts. Gaoligong, China. Feddes Repertorium110: 423-424.

LI H. and WEI Z.X., 1993 – Colocasia heterochroma,a new species of Colocasia from Araceae. ActaBotanica Yunnanica, 15: 16-17.

LONG C.L. and LI H., 2000 – The Chinese Coloca-sia gongii (Araceae), a new species from Yunan,China. Feddes Repertorium, 111: 559-560.

LONG C.L. and LIU K.M., 2001 – Colocasia lihen-giae (Araceae: Colocasieae), a new species fromYunnan, China. Bot. Bull. Acad. Sin., 42: 313-317.

MAYO S.J., BOGNER J. and BOYCE P.C., 1997 – Thegenera of Araceae. The Royal Botanical Garden,pp. 280-283.

MOOKERJEA A., 1955 – Cytology of different speciesof aroids with a view to trace the basis of theirevolution. Caryologia, 7: 221-291.

MARCHANT C.J., 1971 – Chromosome variation inAraceae II. Richardieae to Colocasieae. Kew Bull.,25: 47-56.

OKADA H. and HAMBALI G.G., 1989 – ChromosomeBehaviors in Meiosis of the inter-specific hybrids

between Colocasia esculenta (L.) Schott andC. gigantean Hook. f. Cytologia, 54: 389-393.

PETERSEN G., 1989 – Cytology and systematic ofAraceae. Nord. J. Bot., 9: 119-166.

PFITZER P., 1957 – Chromosomenzahlen vonAraceen. Chromosoma, 8: 436-440.

RAMACHANDRAN K., 1978 – Cytological studies onsouth Indian Araceae. Cytologia, 43: 289-303.

RAO N.S., 1947 – A note on the chromosome num-ber of Colocasia antiquorum Schott. Curr. Sci., 16:229.

SHARMA A.K. and DAS N.K., 1954 – Study of kary-otypes and their alteration in Aroids. Agronomi-al Lusitania, 16: 23-48.

SREEKUMARI M.T. and MATHEW P.M., 1991a – Kary-omorphology of five morphotypes of Taro (Coloca-sia esculenta (L) Schott). Cytologia, 56: 215-218.

–, 1991b – Karyotypically distinct morphotypes inTaro (Colocasia esculenta (L) Schott). Cytologia,56: 399-402.

STEBBINS G.L., 1971 – Chromosomal evolution inhigher plants. London, Edward Arnold.

TANAKA R., 1971 – Types of resting nuclei in Orchi-daceae. Bot. Mag. (Tokyo), 84: 118-122.

–, 1977 – Recent Karyotype Studies. In: Ogawa Y., etal. (Eds.), “Plant Cytology”. Tokyo: AsakuraShoten.

VIJAYA BAI K., MAGOON M.L. and KRISHNAN R.,1971 – Meiosis and pollen mitosis in diploid andtriploid Colocasia antiquorum Schott. Genetica,42: 187-198.

YEN D.E. and WHEELER J.M., 1968 – Introductionof taro into the pacific: the indications of chro-mosome numbers. Ethnology, 7: 259-267.

Received December 5, 2002; accepted April 5, 2003

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