Etiology and Epidemiology of Phytophthora Crown Rot on Pepper Caused by P. capsici Under Waterlogged Conditions

Abstract

Phytophthora crown rot is a destructive disease of pepper caused by Phytophthora capsici, leading to severe plant decline, crown necrosis, wilting, and significant yield losses, particularly under waterlogged soil conditions. Field surveys were conducted across major pepper-growing regions to investigate the etiology, disease incidence, and epidemiological patterns associated with crown rot outbreaks. Symptomatic plants exhibiting crown discoloration, root decay, and sudden wilt were collected for pathogen isolation and characterization. Morphological examination of isolates revealed cottony white colonies with abundant sporangia, oospores, and characteristic hyphal structures typical of P. capsici. Pathogenicity tests on healthy pepper plants reproduced typical crown rot symptoms, confirming the causal role of the pathogen, and Koch’s postulates were fulfilled through successful re-isolation. Molecular identification using PCR amplification and sequencing of ITS and additional conserved gene regions confirmed species identity with high similarity to reference P. capsici isolates in global databases. Phylogenetic analysis clustered field isolates within the P. capsici lineage, indicating genetic relatedness among populations from different agroecological zones. Epidemiological observations revealed that disease incidence was significantly higher in fields with poor drainage and prolonged soil saturation, which favored zoospore production, mobility, and root infection. Warm temperatures combined with excessive irrigation further enhanced disease development and epidemic progression. Spatial analysis indicated patchy disease distribution initially, followed by rapid field-wide spread under conducive environmental conditions. Continuous monocropping and inadequate water management practices contributed to pathogen persistence in soil and increased inoculum buildup.