PRELIMINARY-OBSERVATIONS ON INDUCED POLYPLOIDY IN INDIAN MAJOR CARPS, LABEO-ROHITA (HAM) AND CATLA-CATLA (HAM)

Induction of triploidy and tetraploidy in the Indian major carp rohu, Labeo rohita (Ham.), and tetraploidy in catla, Catla catla (Ham.), and L. rohita were successfully carried out for the first time by administration of thermal shocks to zygotes. Triploidy was induced in rohu by administering heat shock 7 min after fertilization at 42±0.5°C×1-2 min and 12% triploids were obtained, but cold shocks gave negative results. Rohu zygotes exposed to heat shock prior to first cleavage at 39±0.5°C×2 min yielded 70% tetraploids and those exposed to a cold shock regime of 10-15°C×10 min yielded 30-55% tetraploids. In the case of catla, heat shocks to zygotes at 40°C×2 min prior to first cleavage yielded 30-65% tetraploids but cold shocks were not effective. © 1990.