Proc. 2nd Int'l Scientific Meeting Phaseolus Beans Advanced Biotechnology Research Network (1993)
Multiple paternity in common bean (Phaseolus vulgaris L.)
F. J. Ibarra-Perez, J. G. Waines

Evidence for multiple paternity within common bean pods was reported in 1990. Two further field experiments were conducted in 1991 and 1992 at the South Coast Extension and Research Center, lrvine, CA. where high levels of cross-pollination were observed. Hypocotyl color and the shikimate dehydrogenase emzyme (SKDH) loci were used as genetic markers to assess multiple paternity in (Phaseolus vulgaris L.). The highly outcrossed white-seeded cultivar 'Ferry Morse 53' was used as the female parent. This cultivar is homozygous recessive (pp) for hypocotyl color. The cross-pollen source parents included three homozygous dominant (PP) purple hypocotyled, black-seeded cultivars. Two of the parental parents, 'ICA Pijao' and G4459 and the maternal parent FM 53, are of Mesoamerican origin and homozygous for the fast (F) allele at the SKDH locus. The other paternal parent, Black Valentine, is of Andean origin and is homozygous for the slow (S) allele at the SKDH locus. Overall, 6125 pods were obtained from 57 and 111 plants harvested individually in 1991 and 1992, respectively. All progeny, 28938 seeds, were scored for hypocotyl color at the seedling stage. Only the purple hypocotyled seedlings were genotyped for the SKDH locus to trace the source of a particular pollen grain. Multiple paternity within pods was identified in all the pods classified as hybrids, 5.8% and 8.1% in 1991 and 1992, respectively. All multiply-sired pods produced nonhybrid and hybrid seeds. As many as three successful fathers per pod were identified, but my method precluded measuring higher levels of multiple paternity. Most of the multiply-sired pods (about 70%) included nonhybrid seeds plus a single hybrid seed. Ovule position effect within multiply-sired pods was inferred from the nonrandom distribution of hybrid seed within a pod. On average, hybrids occurred more frequently in ovules in position 7 (most basal) and ovules in position 1 (most stylar) than in ovules in the middle positions of the pod.

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