SPOROPHYTIC AND GAMETOPHYTIC COMPONENTS OF THERMOTOLERANCE AFFECTED BY POLLEN SELECTION

This study was undertaken to assess the effect of in vivo male gametop hytic selection on components of thermotolerance in maize, The F-1 bet ween a tolerant (Pa33) and a susceptible (B37) genotype was used as po llen 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 sporophyti c and gametophytic components of thermotolerance, including cellular m embrane stability, heat shock protein synthesis, pollen germination, a nd tube growth rate, Both expression of heat shock proteins 102, 84, a nd 17 kDa and pollen germination ability under a high-temperature regi me were significantly higher in the selected than in the nonselected p rogenies, No response to selection was detected for cellular membrane stability and pollen tube growth rate, These results suggest that poll en selection can serve to improve at least some gametophytic and sporo phytic components of thermotolerance.