Allelism between the P and Stp Genes for Seedcoat Color and Pattern in Common Bean
2003
Bassett, Mark J.
The P locus in common bean (Phaseolus vulgaris L.) can express complete absence of color (white) in seedcoats and flowers with p (with B V) or a pale grayish white seedcoat and nearly white flower with p(gri), but P has never been considered a seedcoat pattern locus. Genes controlling seedcoat colors and patterns have been backcrossed into the recurrent parent 5-593 with black seedcoats and violet flowers. The cross, p BC(3) 5-593 × t stp(mic) BC(3) 5-593 (black seeds with a long white micropyle stripe and fibula arcs), failed to show evidence of genetic complementation in either F(1) or F(2) progeny, leading to the hypothesis that P and Stp are allelic. Five cross combinations between two recessive P alleles (p BC(3) 5-593 and p(gri) BC(3) 5-593) and three recessive alleles at the stippled seedcoat gene Stp (stp BC(3) 5-593, stp(hbw) BC(3) 5-593, and stp(mic) BC(3) 5-593) expressed no genetic complementation in seedcoats and flowers of F(1) progeny and confirmed the allelism hypothesis. New gene symbols are proposed for the recessive alleles at Stp, viz., p(stp) for stp, p(hbw) for stp(hbw) and p(mic) for stp(mic). The dominance order at P is P > p(mic) > p(hbw) > p(stp) > p(gri) > p. Crosses were made between t self-colored BC3 5-593 and three other parents—p(stp) BC(3) 5-593, p(hbw) BC(3) 5-593, and p(mic) BC(3) 5-593-to explore interactions between the pattern genes T and P; and segregation for seedcoat patterns in F(2) was discussed. The hypothesis was proposed that the T locus regulates expression at P, or the biosynthetic step regulated by P.
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