Optimization of Mutant Recovery from plants obtained from gamma-radiated seeds of winged bean (Psophocarpus tetragonolobus (L) DC)

Dry seeds of winged bean (Psophocarpus tetragonolobus (L.) DC) cvs UPS 122 and Kade 6/16 were treated with acute radiation doses of 150 Gy and 250 Gy at a dose rate of 737.32 Gy/hr from a Cobalt-60 gamma source for studies in optimisation of mutant selection in M2 and M3 populations. Mature dry pods were harvested at four different locations on each M1 plant viz. 0.5, 1.0, 1.5 and 2.0 metres from the ground. M2 seedlings we-re screened for different groups of chlorophyll deficiencies and their frequencies. Reduction in chlorophyll mutation frequency from the first formed seeds to the latest ones within the M1 pods has been observed for both cultivars studied. The high degree of chimerism recorded in the M2 seedlings present in the first-formed seeds in the M1 pods provides a clear indication that these seeds constitute a zone from which seeds for the M2 generation have to be harvested in order to give the highest probability for obtaining different types of mutants. On the other hand, significant differences in mutation frequency were not obtained in M2 seedlings from pods harvested at the various positions on the M1 plants. M1 pods can be harvested at any height on the M1 plant, but it is preferable to use the earliest mature ones to save time and labour. The zones identified on M1 plants in this investigation coupled with the use of the "spare" or "remnant" seed selection method, should provide an improved method for mutation breeding in a viny legume like the winged bean. Journal of Applied Science and Technology (JAST) , Vol. 5, Nos. 1 & 2, 2000, pp. 56 - 6