Abstract

Angular leaf spot (ALS) caused by Pseudocercospora griseola is the most economically damaging common bean (Phaseolus vulgaris L.) foliar disease in Democratic Republic of Congo (DRC) and elsewhere in Eastern and Central Africa. Information regarding pathotypes distribution and genetic structure that would enable development of appropriate control measures is still lacking in DRC. The study aimed to investigate the pathogenic and genetic structure of P. griseola isolates from two agro-ecological zones of eastern DRC. Virulence analysis of 59 P. griseola isolates, using differential cultivars, identified 35 pathotypes groups. Most virulent pathotypes were discerned in sub-humid highlands area: Repetitive PCR primers, BOXAIR and REP used to elucidate genetic diversity revealed high level of polymorphism (95.5%), influence of agro-ecology and host genotypes on P. griseola population structure; with moderate genetic differentiation, respectively (G_ST= 19% and G_ST= 12%). Low genetic diversity(D_ST) value revealed that most of the genetic  variability was within subpopulations (96%), with little variability between P. griseola sub populations from the host genotypes (4%). The cluster analysis using UPGMA method identified two main clusters at 65% genetic similarities. The study confirmed that P. griseola populations from eastern DRC, can be broadly grouped into two structured host genotype groups and co-evolution process. This implies that screening for ALS resistance should consider this high diversity for an appropriate breeding program and durable disease management strategies development.

Key words: Pathotypes, agro-ecology, common bean, genetic distance, durable resistance.