Genetic Diversity of Phaeoisariopsis griseola in Kenya as Revealed by AFLP and Group-specific Primers

Genetic diversity of 50 Phaeoisariopsis griseola isolates collected from different agroecological zones in Kenya was studied using group-specific primers and amplified fragment length polymorphism (AFLP) markers. Group-specific primers differentiated the isolates into Andean and Mesoamerican groups, corresponding to the two common-bean gene pools. Significant polymorphisms were observed with all the AFLP primer combinations used, reflecting a wide genetic diversity in the P. griseola population. A total of 207 fingerprints was generated, of which 178 were polymorphic. Cluster analysis of the polymorphic bands also separated the isolates into the two groups defined by groupspecific primers. All the isolates examined were grouped into three virulence populations; Andean, Afro-Andean and Mesoamerican, and their genetic diversity measured. On average, greater diversity (91%) was detected within populations than between populations (9%). The genetic distance between Andean and Mesoamerican populations was higher (D ¼ 0.0269) than between Andean and Afro-Andean (D ¼ 0.0095). The wide genetic diversity reported here has significant implications in breeding for resistance to angular leaf spot and should be taken into consideration when screening and deploying resistant bean genotypes