Author(s):

P Karthikeyan, M Venkatesan and G Suganya

Abstract: Rice (<em>Oryza sativa</em>, 2n=2x=24) belongs to family Poyeaceae is the major food crop of the world for more than half of the global production. The genetic improvement through plant breeding has been an effective mechanism to improve the yield potential of this crop. <em>per se </em>performance largely governs the yield of the crop. The present investigation was carried out at the plant breeding farm, Department of Genetics and Plant Breeding, Faculty of Agriculture, Annamalai University. To study the genetic variability, heritability and genetic advance of mutant generations (M₁, M₂ and M₃) in PY-5 by employing gamma rays in combination with 1% EMS treatments. In the M₂ generation, chlorophyll mutants namely albino and xantha were observed and few viable mutants like grassy leaf, spreading, narrow leaf, pigmented and lax panicle were observed. The results of two generations were revealed that there was a general reduction in characters like plant height and 100 grain weight. There was a general increase in most important economic characters like number of productive tillers per plant and grain yield per plant. Among the treatments studied, 15KR+1 percent EMS treatment was more effective in inducing mutation in M₂ generation when compared to other combination treatments. The genetic variability was found to be wider in M₂ generation and narrowed down and attained homozygosity in M₃ generation. High heritability coupled with high genetic advance as percent of mean was registered in grain yield per plant in both generation. This indicated that the above trait was least influenced by environment and mostly governed by additive gene action. Therefore this trait can be improved through pedigree selection. Among the sibs studied, sib7 was found to be superior for grain yield per plant and productive tillers per plant.

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