A comprehensive review on angular leaf spot disease of beans (Phaseolus vulgaris L) caused by Peudocercospora griseola (Sacc.) Crous & Braun

Abstract

Cercosporoid fungi are one of the largest and most economically important groups of plant pathogenic fungi causing a variety of leaf spots across diverse crop species including beans and may cause significant yield loss as well as deterioration of pod and seed quality. The widespread occurrence and high pathogenic success of Cercosporoids has been attributed to a highly toxic and photoactivated metabolite, cercosporin, visible in mycelia as well as a high degree of pathogenic variability. Angular leaf spot of beans caused by Pseudocercospora griseola, has a broad host range including cultivated bean species, Vigna, Pisum, Desmodium, and Lablab. Currently, disease is managed by a combination of cultural and chemical management strategies, which is ecologically unsustainable. The resistance to P. griseola is governed by both dominant and recessive genes. Currently, six genes namely Phg-1, Phg-2, Phg3, Phg-4, Phg-5 and Phg-6 are reported in common bean. The Phg-1, Phg-4, and Phg-5 genes are from an Andean origin, and the Phg2 and Phg-3 genes are from a Mesoamerican origin. Phg-1 and Phg-2 are dominant resistance genes mapped on chromosomes Pv01 and Pv08 respectively. Various QTLs have also been associated with ALS resistance in beans. The known resistance sources as well as the availability of genetic and genomic resources, coupled with a better knowledge of biology, and pathogenicity have advanced our understanding of angular leaf spot and developed resistant cultivars for a sustainable bean production system, especially in low input small holder farming systems. This review presents updated information on various aspects of disease and research efforts towards effective management.