Morphological and Molecular Characterization of Phytophthora Species Causing Crown Rot on Strawberry in Highland Fields

Abstract

Crown rot of strawberry caused by Phytophthora species is a destructive soilborne disease in highland production systems, leading to plant collapse and significant yield losses. The present study aimed to characterize Phytophthora spp. associated with crown rot in strawberry using integrated morphological and molecular approaches. Diseased plants exhibiting wilting, crown browning, and root decay were collected from highland fields, and pathogens were isolated on selective media. Cultural characteristics including colony morphology, growth rate, and sporulation patterns were recorded, while microscopic examination revealed distinctive sporangial shapes, papillate structures, and oospore formation typical of Phytophthora species. Considerable morphological variability among isolates suggested the presence of multiple species within the genus. Molecular identification was performed using ITS rDNA and cytochrome oxidase subunit I (COI) gene sequencing, which confirmed the presence of distinct Phytophthora species associated with crown rot symptoms. Phylogenetic analysis revealed clear clustering of isolates into separate lineages, indicating genetic diversity within pathogen populations in strawberry fields. Pathogenicity tests on healthy strawberry plants reproduced typical crown rot symptoms, fulfilling Koch’s postulates and confirming the virulence of all tested isolates. Disease development was favored by cool temperatures and high soil moisture conditions typical of highland environments, which enhanced zoospore production and infection efficiency. The study highlights the complex etiology of strawberry crown rot involving multiple Phytophthora species and underscores the importance of accurate molecular diagnostics for disease management. Overall, the findings provide valuable insights into the morphological diversity, molecular identity, and pathogenic variability of Phytophthora spp., supporting improved strategies for disease monitoring and integrated management in strawberry production systems.