SELF-COMPATIBILITY AND AUTOGAMY OF HYBRIDS AND THEIR PARENTS IN SUNFLOWER (HELIANTHUS ANNUUS L.) (HAWAII, CALIFORNIA, MINNESOTA)

This study demonstrated the need to maximize self-pollination to obtain valid estimates of self-compatibility. Autogamous pollination estimates were lower for most genotypes than estimates based on manipulated seed set (self-compatibility as defined in this study). Genotypes with a large pollination requirement (that is, self-compatibility percentage less autogamous pollination percentage) were also less bee attractive. Genotypes with a large pollination requirement will suffer reduced seed set and yield in commercial plantings where pollinators are inadequate. Selection for high autogamous pollination would satisfy the need for cultivars both highly self-compatible and highly self-pollinating.;Tests of genotypes at three locations, Kauai, Hawaii, Woodland, California (four planting dates), and Moorhead, Minnesota indicated possible environmental factors affecting autogamy and self-compatibility. High day temperatures (greater than 31 C) may have reduced autogamy and self-compatibility. Short photoperiods (11 hours) at Kauai appeared to drastically reduce these values.;Fully self-compatible genotypes were stable across environments. Genotypes with lower self-compatibility were unstable across environments. Genotypes selected for high self-compatibility should be tested in their area of release.;Heritability estimates for self-compatibility and autogamy indicated selection would be effective for some populations. Non-additive genetic variance was important.;A large range in autogamy was found for genotypes studied. No genotype was fully autogamous. Some reduction in autogamy could be tolerated in commercial cultivars because increase in seed size will compensate for reduced seed number in maintaining yield.;Pollen tube studies revealed no correlation between autogamy and pollen tube number. Most pollen tubes in poorly autogamous genotypes must be ineffective in fertilization or embryo abortion occurred. Manipulation increased seed set of poorly autogamous genotypes indicating that either pollen quantity or differential timing of pollination (manipulation over the flowering period) was more important than pollen transfer.;Low autogamous pollination was associated with pronounced head inclination. Isolation studies were inconclusive in showing the contribution of other florets to autogamous pollination.