Pathogenicity and Molecular Diversity of Phoma spp. Associated with Stem Canker of Brassica Oilseed Crops

Abstract

Stem canker caused by Phoma spp. is one of the most destructive diseases affecting Brassica oilseed crops, leading to significant reductions in plant vigor, seed yield, and oil quality. The disease is characterized by stem lesions, tissue necrosis, premature senescence, and lodging under severe infection conditions. Accurate identification and characterization of the causal pathogens are essential for effective disease management and resistance breeding programs. The present study was undertaken to investigate the pathogenicity and molecular diversity of Phoma species associated with stem canker disease in Brassica oilseed crops. Diseased plant samples exhibiting characteristic stem canker symptoms were collected from major cultivation areas, and fungal isolates were obtained through standard isolation techniques. Pathogenicity tests were conducted under controlled conditions to evaluate the virulence of different isolates on susceptible Brassica hosts. Molecular characterization was performed using polymerase chain reaction (PCR) amplification and sequencing of conserved genomic regions to assess genetic diversity and phylogenetic relationships among the isolates. The results confirmed the association of multiple Phoma isolates with stem canker symptoms, although considerable variation in pathogenicity was observed among the tested isolates. Several isolates exhibited high virulence, causing extensive lesion development and severe stem damage in inoculated plants. Molecular analysis revealed substantial genetic diversity within the Phoma population, indicating the presence of distinct phylogenetic groups associated with Brassica crops. Sequence comparison demonstrated close similarity between the identified isolates and previously reported pathogenic Phoma species affecting oilseed crops worldwide. The findings of this study provide important insights into the epidemiology and genetic variability of Phoma spp. associated with stem canker disease. Understanding the pathogenic and molecular diversity of these fungal pathogens is essential for developing effective disease management strategies, resistant cultivars,