Relationships between pollen-ovule ratio and autofertility, self-compatibility, automatic self-pollination ability in heterogeneous incomplete autogamous plants, Thai mustard

It is generally recognized that the pollen-ovule (P/O) ratio is correlated with the breeding system of plant species; the higher the P/O ratio, the lower the autogamy among species. Evaluation of breeding systems before flowering is useful for the selection of predominantly autogamous breeding materials from heterogeneous incomplete autogamous plants. We analyzed the correlation between the breeding system and P/O ratio in a Thai mustard cv. Knock out with low autofertility (AF). Automatic self-pollination ability (ASPA) ranged from 29.4% to 52.8%, and ASPA of a line S-6-3 was significantly higher than in the original population. Among 8 S-6 lines derived from one So plant by recurrent seed growing after automatic self-pollination, we observed significant negative linear regression equations between AF and the P/O ratio as well as between ASPA and the P/O ratio. These results indicate that the higher AF, particularly ASPA, the lower the P/O ratio even within the selected lines in a local mustard cultivar. Consequently, evaluation of the P/O ratio in flower buds before flowering is a promising method for the selection of breeding materials with high ASPA from heterogeneous incomplete autogamous or allogamous plants with a similar self-compatibility.