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Chili pepper (Capsicum annum L.) is an important economic crop that is severely destroyed by the filamentous oomycete Phytophthora capsici. Little is known about this pathogen in key chili pepper farms in Punjab province, Pakistan. We investigated the genetic diversity of P. capsici strains using standard taxonomic and molecular tools, and characterized their colony growth patterns as well as their disease severity on chili pepper plants under the greenhouse conditions. Phylogenetic analysis based on ribosomal DNA (rDNA), β-tubulin and translation elongation factor 1α loci revealed divergent evolution in the population structure of P. capsici isolates. The mean oospore diameter of mating type A1 isolates was greater than that of mating type A2 isolates. We provide first evidence of an uneven distribution of highly virulent mating type A1 and A2 of P. capsici that are insensitive to mefenoxam, pyrimorph, dimethomorph, and azoxystrobin fungicides, and represent a risk factor that could ease outpacing the current P. capsici management strategies.

A survey was conducted in chili and a leaf spot disease with approximately 46% incidence was observed in the field. Morphological characteristics of the isolates correspond to those reported for Phytophthora capsici. The resulting sequences of ITS and TEF1 gene had high similarity after BLAST analysis with those of P. capsici isolates. The pathogenicity of one isolate was tested by spraying the zoospore suspension and symptoms of leaf spots similar to those observed in the field developed on all the inoculated leaves. [ABSTRACT FROM AUTHOR]