Morpho-molecular identification and pathogenicity of Ralstonia solanacearum associated with bacterial wilt in Cabintan, Philippines

Abstract Ralstonia solanacearum , the causal agent of bacterial wilt, is an important pathogen of vegetable crops. Despite its occurrence in Eastern Visayas, limited information is available on bacterial wilt-associated Ralstonia in Barangay Cabintan, Ormoc City, Leyte. This study aimed to identify bacterial isolates associated with bacterial wilt using morphological and molecular approaches and to evaluate their pathogenicity on selected tomato varieties. Isolates were obtained from symptomatic tomato and potato plants and soil samples through pathogen baiting. The isolates showed typical R. solanacearum characteristics on Tetrazolium Chloride Agar, including creamy to light pink, fluidal colonies, and were Gram-negative. 16S rRNA gene sequencing confirmed their identity as members of the R. solanacearum species complex, with high nucleotide similarity to reference sequences. Pathogenicity testing using Avatar TY F1, Diamante Max F1, and Jewel F1 showed differences in disease development among isolates. The VSU isolate caused 100% infection in all three varieties and showed the highest disease progression and AUDPC values, while Cabintan isolates generally showed lower disease development. Although numerical differences were observed among varieties, these were not statistically significant; all varieties responded to one isolate in the same manner. The study confirms the identity and pathogenicity of bacterial wilt-associated Ralstonia isolates from Cabintan and provides baseline information for further studies on pathogen diversity, varietal response, and disease management.