Effects of temperature during microsporogenesis on pollen performance in Cucurbita pepo L. (Cucurbitaceae)

This study uses a wild and cultivated variety of Cucurbita pepo to examine the effects of temperature during pollen development on pollen performance and to examine the extent to which the effects of temperature on pollen performance are environmental or genetic. We found that pollen developed at 20°C (cool temperature) grew significantly longer pollen tubes in vitro than pollen developed at 30°C (warm temperature), and it sired significantly more seeds in competition with pollen developed at 30°C. Developmental temperature not only affected the speed of pollen tube growth in vivo, but it also affected the resulting sporophytic generation. Seeds sired by cool- and warm-developed pollen did not differ significantly in seed weight, but seeds sired by cool-developed pollen had significantly faster root growth after 24 h and 48 h, significantly greater seedling mass after 48 h, and larger leaf area at 7 d than seeds sired by warm-developed pollen. This indicates that at least some of the effects of temperature on pollen performance had a genetic basis. We also examined the segregation of four single gene morphological traits in backcrosses using pollen from F₁ plants (cultivated ♀ x wild ♂ C. pepo) developed under warm and cool conditions. For one trait, the allele from the cultivar was found in a significantly higher percentage of the progeny sired by cool-developed pollen than in the warm-developed pollen, possibly indicating that the gene for this trait is linked to a temperature sensitive gene.