Self fertilization and seed set in Trifolium repens L. by in situ and in vitro pollination.

The frequency of seed formation has been determined from self-pollination in situ (by hand) and in vitro for Trifolium repens. Selfing in situ was measured over a period of 3 years in which plants were held either at 35 °C for 24 h post-pollination (1984 and 1985) or held at ambient temperatures (1986). Mean yield of self-seed per 100 florets was 2.8 in 1984, 5.2 in 1985 and 2.2 in 1986. This was based on over 15,000 selfings per year with seven varieties and a total of 166 genotypes. In general, seed set following self-pollination was low; 53% of all genotypes set less than one seed per 100 florets selfed. Selfing of 340 excised florets in vitro with six genotypes gave a mean of 30.6 seeds per 100 florets. Temperature treatments (post-pollination) had no significant effect on seed yield in vitro. Treatment of florets in vitro for 24 h post-pollination with 0.1% CO2 increased the yield of self seed with three genotypes but had no effect on a fourth genotype.