Successful induction of polyploidy using colchicine is a well established phenomenon and still remains a potential cytological technique to induce numerical variations in plants. Since the discovery of Blakslee and Avery in 1937 about the chromosome doubling property of colchicine, enormous number of papers have been published on colchicine induced polyploidy. However, this technique was found to be more promising in popular ornamentals and veg etatively propagated plants. But, for some unknown reasons, induction of polyploidy in legumes was found rather difficult. A review of literature reveals that very few reports on suc cessful induction of polyploidy in legumes (Sen and Chedda 1958, Biswas and Bhattacharya 1971, Singh and Roy 1971, Gupta and Gupta 1975, 1976, Raghuvanshi and Singh 1977, Singh and Gopal 1979 are available in comparison to large number of reports on popular ornamentals Jalil et al. 1974, Arora 1975, Zadoo et al. 1975, Srivastav and Raina 1981, Rao et al. 1982.Trigonella foenum-graecum (commonly known as "Methi" or "Fenugreek") of family Leguminosae and subfamily Papilionaceae, is extensively grown in tropical and subtropical regions of India for its vegetable value and seeds which are medicinally important. The present study was undertaken in a view to study the cytomorphological features of T. foenum -graecum polyploids in successive generations and to explore the possibility of evolving a high yielding variety in terms of vegetable value and improved seed-set.
Material and methodsSeeds of T. foenum-graecum used for colchicinization were obtained from Central Arid Zone Research Institute, Jodhpur.For colchicinization three methods viz. seed treatment, cotton-swab and cotyledonary leaves immersion methods were tried. The treatment was carried out for 12 or 18 hrs spread over 2 or 3 days with 0.15% colchicine (Sigma). For meiotic analysis buds were collected and fixed in iron acetic-alcohol overnight. Anthers stained in leucobasic-fuchsin were squashed in 1% aceto-carmine. Microphotographs were taken from temporary preparations.
ObservationsOf the all the three methods employed, successful induction of polyploidy was achieved mainly by cotton swab method and partially by cotyledonary leaves immersion method (Table 1). Seed germinated after the treatment. Out of seventy seedlings treated by cotton-swab method with 0.15% colchicine for 12 or 18 hrs equally spread over three days, six were cyto logically confirmed as autotetraploids. Only one out of 22 seedlings treated for 10 hrs by cotyledonary leaves immersion method was found to be autotetraploid on cytological analysis.Swelling of the apical region of the seedlings was the immediate effect of coichinization,