INTERACTION BETWEEN COLLETOTRICHUM-LINDEMUTHIANUM RACES AND GENE POOLDIVERSITY IN PHASEOLUS-VULGARIS

Sixty-two genetically diverse modern and traditional Phaseolus vulgari s L. cultivars from Brazil, the Dominican Republic, Honduras, Mexico, the Netherlands, and the United States, representative of the Andean a nd Middle American gene peals, were selected to study the interaction with distinct races of Colletotrichum lindemuthianum (Sacc, & Magnus) Lams.-Scrib. Principal component and phenetic analyses were conducted on tbe disease reaction to inoculation with 34 races of C. lindemuthia num from Argentina, Brazil, Colombia, Costa Rica, the Dominican Republ ic, Honduras, Mexico, Peru, and the United States. The principal compo nent analysis revealed four clusters in which only one cluster consist ed of cultivars from both gene pools. Bean genotypes clustered based o n the gene pool origin of the resistance genes present, regardless of the actual gene pool of the host genotype. Middle American genotypes i n cluster A carried Andean resistance genes. Further grouping of genot ypes based on overall level of resistance within each gene pool was ob served. Clusters A and C consisted of the most resistant genotypes fro m both gene pools. The distribution of genotypes generated by the phen etic analysis, placed the most resistant and susceptible genotypes of the anthracnose differential series at the extremities of the phenogra m, providing support for the range in genotypic resistance exhibited b y members of the differential series. Races of C. lindemuthianum isola ted from Middle American genotypes showed broad virulence on germplasm from both gene pools, whereas races with Andean reaction showed high virulence only on Andean germplasm, The reduced virulence of Andean ra ces on Middle American genotypes suggests selection of virulence facto rs congruent with diversity in P. vulgaris. In addition, races of C. l indemuthianum formed two clusters corresponding to the Middle American and Andean reaction groups based on the phenetic analysis. In the pri ncipal component analysis, most races with the Andean reaction were ob served in the clusters C and D, except races 15 and 23 which clustered with Middle American races in cluster B, Only races 38, 39 and 47 fro m the Dominican Republic showed high similarity in both multivariate a nalyses and clustered based on geographic origin. Races from other cou ntries showed no geographic effect. The overlapping of specific races, however, with races from different reaction groups might indicate tha t this group of isolates possesses factors of virulence to both host g ene pools. Data based on virulence supports variability in C. lindemut hianum structured with diversity in P. vulgaris.