Fertility Losses in Congruity Backcross (CBC), Intraspecific Phaseolus vulgaris Hybrids

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  • 1 Dept. of Horticultural Science, Univ. of Minnesota, St. Paul, MN 55108

Decreases in fertility are most common among interspecific, wide crosses of Phaseolus; intraspecific hybrids are less likely to exhibit sterility. Intraspecific CBC hybrid pedigrees were created to test for comparative fertility losses. Eight P. vulgaris cultivars from different centers of origin, polymorphic for seed proteins (15, 20, 50 kDa), were used to create 16 CBC populations: dry (`Cuarenteño', `Great Northern Harris', `Sulfur', `Swedish Brown') and snap beans (`Purple Pod Pole', `Romano Bush', `Royal Burgundy Bush', `White Half Runner'). Despite repeated attempts, two crosses failed to produce primary hybrids. Primary hybrids had decreased percent stainable pollen from the parents. Female sterility was more severe, necessitating the screening of the F1–F3 before producing the next CBC. Yield was significantly lower than midparent values for all F3 CBC pedigrees. In several cases, phaseolin was no longer the major seed protein. Other hybrid breakdown symptoms were similar to those found with wide crosses, indicative of incongruity between centers of origin.

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