RFLP ANALYSIS OF PREFERENTIAL TRANSMISSION IN INTERSPECIFIC HYBRIDS OF PHASEOLUS-VULGARIS AND P-COCCINEUS

The inheritance of RFLP markers in interspecific hybrids of Phaseolus vulgaris and P. coccineus was analyzed. Of 280 cDNA probes used, 70%-8 5% revealed polymorphism between species while intraspecific RFLP rang ed from 8% to 37%. Segregation of 63 clearly scorable markers was exam ined in 177 P. vulgaris x P. coccineus F-2's maintained as callus. Pre ferential transmission of the P. vulgaris alleles was observed for 24 of the 28 loci exhibiting non-Mendelian ratios. Although the segregati on ratios at 17 loci fit gametic selection, also other factors such as nuclear-cytoplasmic or embryo-endosperm interactions may be involved. In the reciprocal F-2, a relatively high frequency of maternal allele s was recovered for several loci, while the paternal allele was favore d at others. The cDNA clone detecting the most extreme segregation, wi th no P. coccineus type detected among 165 P. vulgaris x P. coccineus F-2 progeny, showed high homology to histone H2A genes. The markers we re mapped to nine linkage groups. Aggregation of markers with preferen tial maternal transmission was observed, which could be due to selecti on of individual chromosomes, although false linkage detection cannot be excluded. The results obtained with RFLPs may explain the skewed di stribution of phenotypic traits following interspecific hybridization.