Cytology of diploid and induced autotetl'aploid of ginger (Zingiber officinale&nbsp;Rosc.) was studied. The diploid (2n=22) showed one or two associations offour chromosomes at first metaphase. The tetraploid formed a high frequency of quadrivalents at first metaphase. Both showed bridge-fragment configurations at first anaphase. Pol1en fertility was 13% in the diploid and 85% in the tetraploid.
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NAIR, K RAMACHANDRAN, P N CHANDRASEKHARAN

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Journal of Spices & Aromatic Crops 1 (2) : 125-130, 1992 125 Cytological studies on diploid and autotetraploid ginger (Zingiber officinale Rose.) K RAMACHANDRAN AND P N CHANDRASEKHARAN NAIR Department of Botany, University of Kera.la Trivandrum - 695 581, India. ABSTRACT Cytology of diploid and induced autotetl'aploid of ginger (Zingiber officinale Rose.) was studied. The diploid (2n=22) showed one or two associations offour chromosomes at first metaphase. The tetraploid formed a high frequency of quadrivalents at first metaphase. Both showed bridge-fragment configurations at first anaphase. Pol1en fertility was 13% in the diploid and 85% in the tetraploid. Key words: ginger, Zingiber officinale, autotetraploidy, cytol-ogy. Introduction The somatic chromosome number of ginger (Zingiber officinale Rose.) was reported by several workers (Federov 1969; Ramachadran . 1969; Omanakumari & Mathew 1985). All the cultival's hiterto studied showed 2n=22. Autotetl'aploids of ginger (2n=44) were produced by colchicine treatment of sprouting buds on rhizomes (Ramachandran 1982; Ramachandran & Nair 1992). Cytological observations on the diploid and ·· the induced autotetroploid ginger are presented here. Materials and methods The diploid used in this study is a widely grown cultivar 'Maran'. Tetraploids of this clone were induced by coJchicine treab~,ent of sprouting buds on rhizomes as described earlier (Ra'machandran & Nair 1992). The somatic chromosomes of the diploid and tetraploid plants were studied from, root tips pretreated with 0.002 M hydroxyquinoline for 4 h at 4°C, washed in water and fixed in 1:3 acetic alcohol. For meiotic studies, the anthers were dissected out from flower buds and fixed. Slides were prepared by the acetocarmine technique. Results The diploid showed 22 somatic chro-mosomes (Fig. 1). They ranged in length from 1.6 ~ to · 4.3 Jl and had median or submedian centromeres. At meiosis the chromosomes were paired as 11 bivalents (Fig. 2) in 36 out of 68 Ponen Mother Cel1s (PMCs) examined at first metaphase. Multiples of four chromosomes, either as close side by side associations ofbivalents or as chains Ramachandra.n and Nair 126 Figs. 1-7. Zingiber officinale, cliploid (Figs. 1-6 : x 950; Fig. 7 : x 320) 1. Somatic chromosome (2n=22) 2. MI showing 11 II 3. Chain of four chromosomes and 9 II at MI 4. MI showing a heteromorphic divalent and fragment (al'row) 5. Two chromatid bridges and two fragments at AI 6. AI cell with a double chromatid bridge and two fragments 7. Pollen grains of diploid Cytology of ginger 127 i . Figs. 8-13. Zingiber officinale, autotetraploid (Figs. 8-12 : x 950; Fig. 13 : X 320) 8. Somatic chromosomes '(2n=44) 9. MI ceJl showing 11 IV 10. MI showing 1 VIII, 8 IV, 2 II 11. Double chromatid bridge and two fragments at AI 12. Tricentric double bridge and two fragments at AI ,13. Pollen grains of tetraploid Ramachandran and Nair (Fig. 3) were observed in 26 cells. Five cel]s showed seven bivalents and two associations of four chromosomes. A heteromorphic bivalent was observed in one of the cells (Fig. 4). The sma1lest pair of chromosomes occasiona1ly ap-peared as univalents. Anaphase I showed normal disjunction in 32 out of 72 PMCs examined. The others revealed bl'idge-fragment configl,lrations. In 27 cells, a dicentric chromatid bridge and an acentric fragment were observed. In seven otheI~ cells there were two bridges and two fragments (Fig. 5). Acentric fragments occurred in some PMCs without chromatid bridges. In one cell, a double chromatid bridge and two chromatid fragments were observed (Fig. 6). Three chromatid bridges and thl'·ee fragments were found in one ceIL The fragments varied in size (1.0 J.l - 2.4 J.l). At second anaphase, bridges and frag-ments were found in one or both daughter cells in 7 out of 50 PMCs ex-amined. The pollen was 13% stainable (Fig. 7). The tetraploid showed 2n=44 chromo-somes in root tip cells (Fig. 8), At meio-sis the chromosomes formed varying associations. Quadrivalents occurred most frequently. The number of quadrivalents varied from 7 to 11 (Fig. 9), the mean being 9.? per cell, The number of bivalents ranged from 0 to 6 with a mean of 1.8. Tl'ivalents and univalents occurred in a low frequency. Associations of six and eight chromo-somes (Fig. 10) were found in some PMCs. The nlost common config~ra­tion at MI was 10 IV + 2 II. Approxi-mately 80% of the total of 124 PMCs at AI exhibited 22-22 disjunction, the others showing 21-23 (8%) and 20-24 (5%). One or two lagging chromosome were ob-served in 7% of the PMCs. The tetra-ploid showed chromatid bridges 'and Jl28 fragments in 47% of the PMCs at AI. Single chromatid bridges with one fragment, double chromatid bridges with two fragments (Fig. 11) and tricentric double bridges with two fragm'ents (Fig. 12) were found. The ponen grains of the tetraploid were larger than those of the diploid, and 85% of the grains were stainable and wen filled (Fig. 13). Discussion The high sterility in the diploid is prob-ably due to heterozygosity for gross structual changes of chromosomes. The associations offour chromosomes, as they persist through metaphase I of meiosis, suggest heterzygosity for interchanges. The associations of six and eight chro-mOSOlnes in the tetraploid further sup-port this conclusion. The heteromor-phic bivalent and fragment at first met-aphase (Fig. 4) and the bridge-fragment configurations at anaphase can result either from crossing over within het-erozygous paracentric inversion pairing loops or from V-type exchanges between sister and non-sister chromatids at pachytene (Jones 1968; Brandham 1969 & 1977). On the basis of differences in fragment size, it was suggested that the diploid could be heterozygous for three paracentric inversions (Ramachandran 1969). Ginger is not favourable for pachytene studies fQr identifying inver-sion loops due to ~he diffuse nature of prophase stages. It is possible that in ginger I both crossing over wi thin paracentric inversion loops as well as V-type exchanges produce bridge-frag-ment configurations at AI, as reported in Podophyllum (Newman 1966) and Leontodon (Finch 1967). Inversions are widespread in pl1ants with vegetative propagation (Muntzing 1961). The high poll en fertility in the artifi-cially induced' tetraploid 'may be a con-Cytology of ginger sequence of the high frequency (87.3%) of quadrivalents followed by the regu-lar two-by-two AI separation. Quadriv-alent n'equency d.epends on chromosome size and the number and distribution of chiasmata (John & Lewis 1965; Hazarika & Rees 1967). The chromosomes in ginger are of medium siz,e (1.611- 4.3~) and are metacentric or submetacentric. In the diploid all the bivalents commonly form at least two chiasmata, one in each arm. The shapes of some of the biva lents with one arm opened and the other un-opened suggest that probably two chi-asmata, one proximal and the other distal are formed in the unopened arm. In view of the number and dist.tibution of chiasmata in the diploid, a high fre-quency of quadrivalent association may be expected in the autotetraploid. Inspite of high pollen fertility, the tet-raploid did not set seeds. This confirms the sporophytic nature of the incom-patibility systeln in ginger, as it is shown that gametophytic incompatibility usu-ally breaks down in induced polyploids (Lewis 1956; Pandey 1983). If, however, androgenesis can be induced in cultures of tetraploid anthers, diploid plants showing large genetic varjation can di-rectly be obtained, as reported in Pel-argoniwn roseum (Tokumasu & Kato 1979). In P. I'oseum the diploid is male-stel'ile whereas the induced tetraploid has fertile pollen. The androgenic dip-10id plants raised through anther culture of tetl'aploids showed large variation in essential oil content. If androgenesis from cultured anthers of induced tetraploids of ginger proves successful J new improved varieties can be produced by this technique. Ack.nowledgements The authors wish to express their thanks to Prof. (Dr.) Susan Abraham, Head, 129 Department of Botany, University of Kerala, Trivandrum for facilities pro-vided. Financial assistance from the Department of Science, Technology and Environment, Government of Kerala is greatly appreciated. References Brandham P E 1969 Inversion het-erozygosity and subchromatid ex-change in Agave stricta. Chromo-soma (Berl.) 26:270-286. Brandham P E 1977 The meiotic behaviour of inversions in poly-ploid Aloineae. Chromosome (Berl.) 62:69-84. Federov A (Ed.) 1969 Chromosome Numbers of Flowering Plants. Acad. Sci. USSR Komarov Bo-tanical Institute, Leningrad. Finch R A 1967 Natural chromosome variation in Leontodon. Heredity 22:359-386. Hazarika M H & Rees H 1967 Geno-typic control of chromosome behaviour in rye. X. Chromosome pairing and fertility in autotet-raploids. Hered'ity 22:317-332. John B & Lewis K R 1965 The meiotic system. Protoplasmatologia 6: 1-335. Jones GH 1968 Meiotic errors in rye related to chiasma formation. Mutation Res. 5:385-395. Lewis D 1956 Incompatibility and plant breeding. In: Genetics in ~lant Breeding. Brookhaven Symp. Biol. 9:89-100. Muntzing A 1961 Genetic Research. Forlag, Stockholm. Ramachandran and Nair Newman L J 1966 Bridge and fragment aberrations in Podophyllum peltatum. Genetics 53:55-63. Omanakumari N & Mathew P M 1985 Karyomorphological studies on four species of Zingiber Adns. Cytologia 50:445-451. Pandey K K 1983 Cytogenetical basis of self incompatibility, evolution-ary considerations In: (Eds.) Swaminathan M S, Gupta P K & Sinha U Cytogenetics of Crop Plants (pp. 117-155). Macmillan India Ltd., New Delhi. Ramachandran K 1969 Chromosome numbers in Zingiberaceae . . Cytologia 34:213-221. Pot .. Pourri Miscellany Attention researchers! All research workers know that there are many miscellaneous findings that never see the light of publication - just because they may not be very significant, interesting or too small an item to be published as a research paper or as a research note. They remain on the pages of scientists' note books - and often get lost in course of time. This information loss is much more than what is generally realised by the sci- ' ~ritists themselves. 130 Ramachandran K 1982 Polyploidy induced in ginger by colchicine treatment. Curr. Sci. 51:288-289. Ramachandran K & Chandrasekharan Nair P N 1992 Induced tetraploids of ginger (Zingiber officinale Rose.). J. Spices & Aromatic Crops 1:39-42. Tokumasu S & Kato M 1979 Variation of chromosome numbers and essential oil components of plants derived from anther culture of the diploid and the tetraploid in Pel-argonium roseum. Euphytica 28:329-338. The editors of 'JOSAC' offer this col-umn to scientists to publish such mis-cellaneous information - too small to form a paper or note - but helpful in enriching our knowledge on spices and aromatic crops. By doing this, you will be saving such information and knowl-edge. Please send your contributions marked MISCELLANY to the Editor. Limit: 2 pages of typed matter. Photographs are not accepted. Simple drawings or graphs can be incorporated if absolutely essen-tial. We welcome you to use this column! Editor 

Cytological studies on diploid and autotetraploid ginger (Zingiber officinale Rosc.)

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Cytological studies on diploid and autotetraploid ginger (Zingiber officinale Rosc.)

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