Screening advanced potato mutant genotypes against bacterial wilt disease under different agro-ecological zones of Kenya

Host plant resistance is a key tool in the management of plant diseases. Mutant lines (IP1, IP2, IP3 and IP4) were tested against other potato varieties (Shangi, Sherehekea, K. Mpya and Unica) in different agro-ecological zones to ascertain their performance under potato bacterial wilt disease pressures. An experiment was set in an RCBD design with three replications in four different sites, namely, Nyandarua, Elgeiyo Marakwet, Burnt Forest and Moiben. Assessment was done on potato bacterial wilt disease prevalence and severities, as well as host plant status, which were rated on a scale of 1-5. Data obtained were subjected to analysis using statistical software GenStat 16th Edition VSN International Ltd. Different response levels and uniqueness were expressed by each test line across all AEZs, where variety, sites and time intervals (DAS) as well as their interactions had significant effects on disease severity, with different tolerance levels to the pathogen experienced in all the lines. The severity mean of four mutant lines was below 2.0 as per the days after sowing (DAS). Moreover, IP1 (2.0) and IP2 (2.1) had an overall mean across all sites; therefore, they proved a high level of tolerance to the bacterial wilt pathogen, while IP3 (2.4) and IP4 (2.5) were less than the resistant check (2.8) across all the sites and the susceptible check Kenya Mpya (3.2). Hence, there is a need for regular screening of the available genotypes for R. solanacearum management in potato production. The existence of the most tolerant varieties could form a baseline in integrated disease management for sustainable potato production.