A comparison of ovule abortion in self-incompatible and self-fertile linesof white clover (Trifolium repens L.)

Plants of white clover (Trifolium repens L.) cv. Olwen and three genotypes of each of three self-fertile inbred lines of white clover were grown from seed in a bee-proof glasshouse. When in flower, a series of crosses within and between the self-incompatible (SI) and self-fertile (SF) lines was made and ovule growth and seed production measured 7 and 28 days after pollinat ion (DAP) respectively. At harvest, the SF plants had a lower proportion of ovules aborting and more seeds per floret than the SI plants, though the m ean seed weight of the SI plants was greater. Ovule abortion was observed i n both the SF and SI plants though the number of abetted ovules was greater in the SI plants. The stage when abortion occurred also differed. All of t he ovule abortion in the SI plants occurred within a 7-day period after pol lination. In the SF plants, some abortion was observed in this period but a lso between 7 and 28 DAP, when the seed was harvested. This suggested that abortion, up to 7 DAP is due primarily to genetic factors whilst subsequent abortion, between 7 and 28 DAP, is due to non-genetic factors.