Phylogenetic distribution of Ralstonia solanacearum species complex populations in potato in Kenya

Ralstonia solanacearum is a pathogen causing bacterial wilt disease of potato, resulting in 70% potato production losses in Kenya. A study was conducted to determine the diversity of Ralstonia solanacearum species complex strains within the main potato-growing regions of Kenya. Potato tubers were collected from different potato-growing regions of Kenya from visibly wilted potato plants, including tomato and irrigation water and cultured for pathogen isolation. Genomic DNA was isolated from 135 purified cultures of RSSC isolates and PCR amplified using multiplex and sequevar primers targeting the endoglucanase partial gene sequences. Pathogenicity test using R. solanacearum strain (phylotype II sequevar I) was done on Kenya Karibu, Shangi, Chulu, Wanjiku and Money Maker cultivars. Phylogenetic analysis of the partial endoglucanase gene identified two genospecies, R. pseudosolanacearum sp. nov (1.5%) and R. solanacearum (98.5%). All R. solanacearum strains clustered in sequevar I and were distributed in all the potato-growing regions surveyed. The cultivars were grown in a greenhouse for two cycles in a randomized complete block design and inoculated with R. solanacearum strain. The severity scores were assessed and the area under disease progress curve (AUDPC) was determined. All the cultivars tested for pathogenicity exhibited wilting symptoms at varying intervals after infection, with none showing complete resistance to R. solanacearum. Cultivar Shangi exhibited minimum disease severity and progression of 41.14% and AUDPC of 1041.7, respectively while Kenya Karibu was the most susceptible with a high progression rate of 68.24% and AUDPC of 1897.5, respectively. Money Maker, Chulu and Wanjiku showed no significant difference in disease severity depicting a simultaneous rate of infection among them. These findings provide valuable information to better understand the pathogen genetic diversity in Kenya and how it spreads.

Complete Genome Sequence of the Plant Pathogen Ralstonia solanacearum Strain CIAT-078, Isolated in Colombia, Obtained Using Oxford Nanopore Technology

ABSTRACT Moko is one of the main diseases affecting banana and plantain in Colombia. Here, we report the genome sequence of the causal agent, the bacterium Ralstonia solanacearum (Smith) strain CIAT-078, collected in 2004 from affected plantains in central-west Colombia. The assembled genome was obtained using Oxford Nanopore Technology.