A study of allogamy in wild Phaseolus vulgaris L.

This project studied the allogamy level among and within populations of wild P. vulgaris L. by using hipocotyl color as a genetic marker. A subsequent validation of the allogamy levels found was also carried out with a biochemical marker, specifically peroxidase isozyme, of young root tissue which attempted to find a correlation between the isozyme polymorphism with the morphological marker. Six accessions of wild P. vulgaris were selected as male parents and the pigmentation (purple color) of their hypocotyls was used as genetic marker. Three accessions with unpigmented hypocotyls were chosen as female parents. The gene pools (Mesoamerica, Northern Andes, and Southern Andes) to which they belong were also considered. The populations were planted in a CIAT location (Corregimiento El Moral-Cerrito, Colombia, at 3 deg. 44' N, 76 deg. 5' W; 2,000 m.a.s.l.; 13.6 degrees C average annual temperature; 1,181 mm average annual rainfall) under open-pollination conditions. Among the F1 from the female progeny a few individuals with pigmented hypocotyls appeared, suggesting that outcrossing occurred. In fact, for the 30,388 F1, progeny seeds planted in the greenhouse, the average percentage of outcrossing was 1.5 percent, and although, a wide coefficient of variation was present, the Northern Andes genepool always appeared with the highest rates of crossability with Mesoamerica and Southern Andes. Duncan's Multiple Range Test indicated that the highest crossability rate, 8.62 percent, was found between populations from Mesoamerica and Northem Andes. For populations from Northern Andes and Southern Andes, the highest crossability rate was 1.28 percent, whereas populations from Mesoamerica and Southern Andes the highest crossability rate was 0.71 percent; within gene pools, the highest rate, 2.18 percent, was found within Northern Andes. The contrast test showed significant differences of allogamy between Mesoamerica and Northern Andes populations. To study intra-crossability, a Northern Andes population was selected. The accession original population had both pigmented and unpigmented hypocotyls in a 2:3 ratio. Unpigmented females were surrounded by pigmented males, and the field was protected by a natural barrier of P. lunatus. The average outcrossing rate was 8.73 percent. An electrophoretic analysis of young root tissue, using peroxidase isozyme, suggested the possible presence of one locus controlling hypocotyl color. Locus PRX-1 allele 98 from male parents gave the pigmented hypocotyl