Ovule Fertility - A Tool for Selecting High-Fertility Populations of White Clover

A field experiment was conducted lo clarify the factors responsible, for poor seed set in 4 white clover (Trifolium repens L.) cultivars. Although the mean number of ovules per floret was 5.18-5.29, lhe average number of seeds per floret was found to be only 1.23-1.82. A' stain-clearing technique was used to examine the cytoplasmic state of the embryo sac in intact, unfertilised, mature ovules and it was found that 28;33% of ovules per carpel were sterile. The abortion rate of fertilised ovules and immature seeds (7 days after pollination) ranged between 32 and 34%. Beyond this period, ii was observed that only a very small proportion of the total seeds were lost. The observation of high ovule sterility in all 4 cultivars suggests that this factor could offer prospects for obtaining a higher number of ovules developing into seeds by screening for high-fertility populations of while clover.