Consequence of cyclic pollen selection for heat tolerance on the performance of different generations in maize (Zea mays L.)

The reproductive stage in many crops, including maize, is very sensitive to heat stress and the genetic overlap between gametophytic and sporophytic phase gives an opportunity to select superior stress tolerant genotype at gametophytic stage. An attempt was made to evaluate the response of cyclic pollen selection in the F-1 and F-2 generations on the performance of F-3 generation progenies for seed yield and yield contributing traits under natural heat stress conditions. In this direction three groups of F-3 progenies, namely (i) pollen selection in F-1 and F-2 generations (GG), (ii) pollen selection only in F-2 generation (CG), (iii) no pollen selection in F-1 and F-2 generations (CC) were screened for heat stress at Agricultural Research Station (ARS), Bheemarayanagudi. The GG progenies recorded significantly higher chlorophyll content, more number of pollen grains per anther and less pollen sterility compared to CG and CC group of progenies under heat stress. Further, the F-4 progenies obtained through cyclic pollen selection (in F-1, F-2 and F-3) were also tested for heat stress tolerance at seedling stage. The significant improvement for heat stress tolerance was recorded in F-4 progenies derived through cyclic pollen selection as compared to control (no pollen selection for heat tolerance in any generation) F-4 progenies. The results indicated that cyclic pollen selection in F-1,F- F-2 and F-3 generations improved the heat stress tolerance of the progenies in the succeeding generations. To provide genetic evidence for the effect of pollen selection for heat tolerance, the control F-2 (C) and selected F-2 (G) populations were compared for the segregation of SSR markers. The selected F-2 (G) population showed significant deviation from normal Mendelian ratio of 1:2:1 and showed skewness towards the alleles selected from male parent. The results provide strong evidence for an increase in the frequency of parental alleles in the progenies that impart heat stress tolerance.