Genetic evidence of pollen selection mediated phenotypic changes in maize conferring transgenerational heat‐stress tolerance

Abstract

AbstractStructural genes of pollen are expressed in both sporophytic and gametophytic generations. This genetic overlap makes possible superior pollen genotype selection. Pollen selection is more effective than sporophytic selection since more pollen grains can be exposed to selection pressure at the haploid level. In this study, selection pressure was applied in the F1 generation at the pollen level for heat tolerance. The frequencies of heat‐tolerant plants were studied for seed yield in F2 and F3 generations and for seedling heat tolerance in F4 generations. The heat‐susceptible inbred line BTM4 was crossed to heat‐tolerant inbred line BTM6 of maize (Zea mays L.). In response to heat stress, we compared F2 plants produced by selfing of heat‐stressed pollen grains and without heat‐stressed pollen grains. The resulting F2 plants from heat‐stressed pollen grains showed significantly higher seed yield per plant (5.41 ± 0.31 g) than control F2 (2.90 ± 0.19 g) populations under stress. The selected and control F2 plants were also subjected to genotyping using simple sequence repeat (SSR) primers. We observed that the frequency of alleles from tolerant parents was higher in selected F2 populations, providing genetic evidence for positive effect of pollen selection. The heat tolerance of F4 generation progenies of the same cross suggested that the cyclic pollen selection for heat tolerance in F1, F2, and F3 generations has significantly improved the tolerance of progenies. The results from this study demonstrate that the feasibility of this approach seems to be promising for hastening the incorporation of desirable alleles in a short time.