EFFECTS OF POLLEN COMPETITION ON PROGENY PERFORMANCE IN A HETEROZYGOUS CUCURBIT

We used an F1 hybrid of zucchini and its wild progenitor to examine th e effects of pollen competition on progeny performance. We experimenta lly varied the intensity of pollen competition by depositing large or small pollen loads onto stigmas. To separate the effects of pollen com petition from maternal effects, we excised the styles of flowers recei ving the large pollen loads after only the fastest pollen tubes had en tered the ovary. The styles from flowers receiving small pollen loads were excised after both fast- and slow-growing tubes had entered the o vary. Consequently, the mature fruits from the two treatments were sim ilar in seed number and weight. Because our previous studies had revea led that fast- and slow-growing pollen tubes fertilize ovules in diffe rent regions (locations) within the ovary (fast into region 1 and slow into region 3), we examined the vigor of the progeny produced in regi ons 1 and 3 from both large and small pollen loads. The results reveal ed that the progeny from large pollen loads outperform progeny from sm all pollen loads. We also found that for small pollen loads, the proge ny from region 1 outperform the progeny from region 3, which indicates that the progeny produced by the fastest pollen tubes outperform the progeny produced from the slowest.