Sporophytic and gametophytic components of thermotolerance affected by pollen selection

This study was undertaken to assess the effect of in vivo male gametophytic selection on components of thermotolerance in maize, The F-1 between a tolerant (Pa33) and a susceptible (B37) genotype was used as pollen source, Male gametophytic selection was carried out by applying a two-h treatment of 50 degrees C to immature tassels in the field, The resulting F-2 and backcross generations were evaluated for sporophytic and gametophytic components of thermotolerance, including cellular membrane stability, heat shock protein synthesis, pollen germination, and tube growth rate, Both expression of heat shock proteins 102, 84, and 17 kDa and pollen germination ability under a high-temperature regime were significantly higher in the selected than in the nonselected progenies, No response to selection was detected for cellular membrane stability and pollen tube growth rate, These results suggest that pollen selection can serve to improve at least some gametophytic and sporophytic components of thermotolerance.