Selfing in an Alfalfa Seed Production Field

Abstract

Purple‐flowered genotypes of alfalfa (Medicago saliva L.) that were simplex at the P locus (Pppp) were spaced planted and open‐pollinated within a seed production field of Blazer XL alfalfa. Self‐pollination in the field environment was estimated by the frequencies of purple‐ and cream‐flowered progeny from simplex plants. Natural purple‐flower color avoided pollinator preferences found with recessive flower colors. The background level of cream gametes (pp) in Blazer XL and the spaced simplex plants was 5% based on cream progeny of two cream (pppp) male‐sterile clones also planted in the field. Selfing averaged 28% based on greenhouse classified with no competition. Based on progeny that were transplanted in the field, selfing averaged 25% while selfing based on progeny seeded in the field averaged 13%. Direct seeding resulted in fewer cream progeny reflecting decreased survival in competition with hybrid progeny. We observed lower selfing percentages than previous estimates which used recessive flower color markers, but our results were similar to a recent allozyme study.