Allozyme Variability in the Tepary Bean, Phaseolus acutifolius A. Gray

The tepary bean (Phaseolus acutifolius) is the object of renewed interest because it possesses some interesting agronomic attributes such as tolerance to drought and salinity. In order to gain a better understanding of the organisation of its genetic diversity, we have examined patterns of diversity for nine polymorphic enzyme systems representing 12 loci, in a sample of 55 wild and 8 cultivated accessions. Several geographic patterns were identified, including an East-West differentiation, (across the Sierra Madre Occidental mountains), a North-South differentiation, and a localized differentiation. Wild teparies displayed a higher number of polymorphic loci, as well as a higher number of alleles per polymorphic locus compared to cultivars, consistent with previous observations indicating a reduction of phaseolin diversity on domestication. No clearcut separation with respect to isozyme differentiation was observed between P. acutifolius var. tenuifolius and var. acutifolius, further questioning the validity of this taxonomic separation based on leaflet shape.