Estimation of outcrossing rate in common bean

To assess genetic and environmental variation for outcrossing in common bean (Phaseolus vulgaris L.), a bulk of nine purple-hypocotyled (dominant), black-seeded, common bean lines (pollen parents) and six green-hypocotyled (recessive), white-seeded, common bean lines (seed parents) representing Mexican germplasm were used to estimate outcrossing rate. The experiment was conducted at Irvine and Riverside, CA, in mid-May and mid-July of 1989 and 1991. Outcrossing estimates were based on the proportion of purple-hypocotyled progeny from green-hypocotyled parents. Approximately 1400 single-plant families were progeny tested in which 120 278 seedlings were scored for the presence of anthocyanin in the hypocotyl. Of these, 113 246 were classified as selfed progeny and 7031 as hybrid progeny, giving rise to a weighted mean outcrossing rate of 6.9%. Entire progenies from each maternal line were grown and scored, and the minimum and maximum rates of outcrossing observed ranged between 0.0 and 78.0%. Mean outcrossing rate for the six white-seeded lines ranged from 4.41 to 10. 16%. However, differences in outcrossing rate among these lines were not significant, nor were differences between dates of planting, locations, or years. The combined analysis of variance showed significant location x planting date x line interaction and year x location X line interaction, indicating that environmental factors had a strong effect on rate of outcrossing in the lines examined.
Knowledge about the breeding system of a crop is important to design effective breeding schemes to improve that crop. Common bean was listed as a predominantly self pollinating species by [...]