EFFECTS OF POLLEN COMPETITION ON THE REPRODUCTIVE-PERFORMANCE IN CUCURBIT HYBRIDS (CUCURBITACEAE) - F1 AND BACKCROSS GENERATIONS

We examined the effect of pollen competition on the reproductive perfo rmance of Cucurbita F-1 and backcross progeny while attempting to cont rol for nongenetic maternal effects and nonrandom seed abortion as pos sible explanations for the data. We compared the vigor of F-1 and back cross progeny produced from large and small pollen loads under field c onditions. The results from both field studies indicated that the prog eny produced from large pollen loads outperformed the progeny produced from small pollen loads for several measures of vigor. The F-1 progen y produced from large pollen loads germinated faster, and produced 12% more staminate flowers and 9% more pistillate flowers than the progen y from the small pollen loads. Similarly, the backcross progeny produc ed from large pollen loads germinated faster, and produced 8% more pis tillate flowers and 20% more fruits than the progeny from the small po llen loads. This study demonstrates a positive correlation between the size of the pollen load and the vigor of the resulting progeny under field conditions.