Cytologia 39: 91-96, 1974

Pairing Behaviour of Chromosomes in Autotetraploid of Jute (Corchorus capsularis L.)

P. L. Ghosh, P. Paria and S. L. Basak

Department of Genetics and Plant Breeding, University of Kalyani, Kalyani, Nadia, West Bengal, India

Received June 9, 1972

Bhaduri and Chakravarty (1948) reported successful induction of autotetra ploidy in C. olitorius L. and C. capsularis L. Pairing behaviour of chromosomes in induced autotetraploid of C. olitorius was studied by Basak and Biswas (1968). But convincing report of pairing behaviour of chromosomes in autotetraploid of C. capsularis is still lacking. The present paper reports a detail analysis of chro mosome pairing in induced autotetraploid in C. capsularis L.

Material and method

Materials used in this study were two pure breeding varieties; i) Maniksari and ii) JRC-212 and Fl hybrid of Maniksari•~Tripura. Seedlings of diploid

plants at cotyledonary leaf-stage were treated with 0.5% colchicine in 0.7% agar solution for 8 hours. After the treatment the treated region was thoroughly washed with water. Fixation of flower bud and squashing of anthers were exactly same

as followed by Basak and Biswas (1968). Pollen fertility was determinee by stain ing fresh pollen with 1 % propiono-carmine. Photomicrographs were taken from

permanent slides.

Observation

Pairing of chromosomes were studied either at late diakinesis or metaphase I

stage. A total of 164 PMCs were analysed in different C, plants. The total number of univalents, bivalents, trivalents and quadrivalents observed in these 164 PMCs were 127, 420, 59 and 862 respectively (Table 1). Each PMC contained

on an average 0.77 univalent, 2.56 bivalents, 0.35 trivalents and 5.26 quadrivalents. The number and the percentages of PMCs containing different number of quadri valents are presented in Table 2. PMCs to show minimum number of quadri

valents contained at least two in them. Maximum number of PMCs were found to contain 5 quadrivalents in 4n, JRC-212 while in 4n, Maniksari and 4n, Fl of

Maniksari•~Tripura maximum number of PMCs were found to contain 6 and 7

quadrivalents respectively. However, on the average 6 quadrivalents per PMC was the most frequent class. The co-efficients of realization of quadrivalents were found to be different for different autotetraploid stocks (Table 1). The aver

age co-efficient of realization of quadrivalents was 0.75. The autotetraploid of Fl 92 P. L. Ghosh, P. Paria and S. L. Basak Cytologia 39

(Maniksari•~Tripura) had the highest co-efficient of realization of quadrivalents (c. f. Table 1).

Table 1. Chromosomal association in autotetraploid Corchorus capsularis

Different types of quadrivalent configuration found in the present study are shown in Figs. 1 to 4. The respective configurations along with their frequencies and percentages in relation to the total number of quadrivalents observed are presented in Table 3. The most frequent class being the figure of eight shaped quadrivalent (24.59 %). The other worthnoting classes in order of frequency were ring of four chromosomes (19.14%),_??_ shaped quadrivalents (11.72%),

-_??_ shaped quadrivalents (10.32%) and chain quadrivalents (7.65%). The types of configurations besides the above mentioned ones were still less frequent.

Table 2. Frequencies and percentage of PMCs with number of quadrivalents

Chiasma frequency per chromosome i.e. per half bivalent was scored in auto tetraploids and diploids. The average chiasma frequencies per chromosome in autotetraploid and diploid were 0.93 and 0.97 respectively (Table 1). The average pollen sterility, as determined by propiono-carmine staining, in autotetraploids and diploids were 22.33% and 3.50% respectively. Table 3. Frequencies and percentage of different quadrivalent configuration

Figures in parentheses represent percentages. 94 P. L. Ghosh, P. Paria and S. L. Basak Cytologia 39

Figs. 1-4. 1, PMC with two _??_ IV (•¨), One--_??_ IV(•¨•¨), two _??_IV (+•¨), one_??_IV (_??_)

and one_??_ IV (_??_). 2, PMC with two II, one --- IV (+•¨), one --() IV (_??_), two _??_IV(•¨), one_??_ IV (•¨•¨) and one_??_ IV (_??_). 3, PMC with four lI, one _??_ IV (•¨), one_??_ (+•¨),one IV (•¨•¨), one_??_ IV (_??_) and one •• IV (_??_). 4, PMC with two I, four II, two_??_ III _??_(_??_), one IV (_??_), one _??_ IV (+•¨) and one >< (•¨•¨). _??_

Discussion In an autotetraploid all the homologous chromosomes are present four times in a nucleus. Henceunivalents, bivalents, trivalents and quadrivalents are expected to form in PMCs. This expectation was realized in the present study in auto tetraploid of C. capsularis and no multivalent involving more than four chromo somes were observed. Earlier Dutta and Panda (1963) reported the occurrence of pentavalent in the form of ring in addition to univalents, bivalents, trivalents and quadrivalentsin autotetraploid of C. capsularis. Both the species of cultivated 1974 Pairing Behaviour of Chromosomes in Autotetraploid of Jute 95 jute, C. capsularis and C. olitorius, are strictly diploid as revealed from their diploid pairing behaviour. Hence a pentavalent and that too in the form of ring as re ported by Dutta and Panda (1963) seems to be highly doubtful as it is not possible to form a pentavalent ring by five homologous chromosomes unless one of them is an isochromosome. The coefficient of realization of quadrivalents in autotetraploid of C. capsularis was found to be very high and ranged from 0.72 to 0.87 in contrast to 0.57 in C. olitorius (Basak and Biswas 1968). Chiasma frequency per chromosome in tetra ploid of the former species was 0.93 and was not greatly different than that of the latter species which was 0.88 (Basak and Biswas 1968). Therefore the observed difference between these two species regarding the coefficient of realization of quadrivalents is not due to the difference in their ability to form chiasmata. Two other factors such as the length of chromosome and the position of centro mere could be the reasons for this interspecific difference in the realization of quad rivalents. Relatively higher frequency of quadrivalents in the form of ring or chain was reported in the autotetraploids of Lycopersicon esculentum (Upcot 1935), Lolium perenne (Dawson 1962) and Corchorus olitorius (Basak and Biswas 1968). Cor chorus capsularis fails to realize this form where quadrivalents in the form of figure of eight is most frequent (24.59 %), and rings and chains are relatively less frequent.

Summary In autotetraploid of jute (Corchorus capsularis) coefficient of realization of quadrivalents was found to be very high (0.75). A PMC on an average found to contain 0.77 univalent, 2.56 bivalents, 0.35 trivalents, and 5.26 quadrivalents. All types of quadrivalent configurations were observed of which figure of eight were most frequent (24.59 %). Chiasma frequency per chromosome were found to be 0.97 and 0.93 in diploid and tetraploid respectively.

Acknowledgement The authors are grateful to Head of the Department of Genetics and Plant Breeding, Kalyani University and to Dr. S. Dana for his interest in this study. One of us (P. P.) is grateful to K. U. for providing him pre-doctoral scholarship.

References

Basak, S. L. and Biswas, P. K. 1968. Pairing behaviour of chromosomes in autotetraploid of jute (Corchorus olitorius L.). Cytologia 33: 50-53. Bhaduri, P. N. and Chakravarty, A. K. 1948. Colchicine induced autotetraploid jute, Corchorus capsularis and C. olitorius and the problem of raising improved varieties. Sci. and Cult. 14: 212-213. Dawson, G. W. P. 1962. An Introduction to the Cytogenetics of Polyploids. F. A. Davis Co., Philadelphia. 96 P. L. Ghosh, P. Paria and S. L. Basak Cytologia 35

Dutta, R. M. and Panda, B. S. 1963. Further studies on meiotic chromosome pairing and sporad analysis in the population of 4n cultivated Corchorus capsularis L. (strain D 154). Ind. Agric. 7: 128-132. Upcott, M. B. 1935. The cytology of triploid and autotetraploid Lycopersicum esculentum. Jour, Genet. 31: 1-19.