Jane Muthoni

Response of Potato Genotypes to Bacterial Wilt Caused by Ralstonia Solanacearum (Smith)(Yabuuchi et al.) In the Tropical Highlands

Potato varietal resistance to bacterial wilt disease caused by Ralstonia solanacearum Yabuuchi et al., (Microbiology and Immunology 39:897–904, 1995) is the best management of the disease. Because the causal pathogen exhibits strong host-pathogen-environment interaction, screening the potential parents for resistance under the target growing environmental conditions is the first important step for effective resistance breeding. The objective of this study was to determine the response to bacterial wilt of selected potato genotypes currently grown by farmers in Kenya and candidate clones from the International Potato Center to identify parents that can be used in the local breeding program to develop resistant cultivars. A study was carried out at Kabete, Kenya for three consecutive seasons between November 2011 and February 2013. Thirty six potato genotypes were planted on an inoculated field at the Kenya Agricultural Research Institute (KARI), Kabete using alpha lattice experimental design with three replications. Data collected were days from planting to onset of wilting (DTOW), bacterial wilt incidence (BWI), total tuber weight (ton ha−1) (TTW), total tuber numbers/hectare (TTN), proportion of ware sized tubers (PWTTW), proportion of symptomatic tubers based on weight (PSTTW), proportion of symptomatic tubers based on tuber numbers (PSTTN) and latent infection (LI) of the tubers. Almost, all the potato genotypes evaluated in this study were susceptible to bacerial wilt. Ranking of genotypes based on resistance differed among the three seasons. On average, the three most resistant genotypes were Kenya Karibu, Kenya Sifa and Ingabire. The study identified eight potato genotypes (Meru, Ingabire, Kenya Karibu, Sherekea, Kihoro, Tigoni, Bishop Gitonga and Cangi) to be used as promising parents for subsequent crosses. The chosen genotypes are prolific in pollen production and popularly grown by Kenyan farmers.ResumenLa Resistencia varietal de la papa a la enfermedad de la marchitez bacteriana, causada por Ralstonia solanacearum Yabuuchi et al., (Microbiology and Immunology 39:897–904, 1995), es el mejor manejo de la enfermedad. Considerando que el agente patógeno causal presenta una interacción fuerte hospedante-patógeno-ambiente, las pruebas de padres potenciales para resistencia bajo condiciones ambientales de crecimiento enfocadas, es el primer paso importante para el mejoramiento efectivo para la resistencia. El objetivo de este estudio fue determinar la respuesta a la marchitez bacteriana de genotipos de papa selectos que actualmente se cultivan por productores en Kenia y clones candidatos del Centro Internacional de la Papa, para identificar padres que pudieran usarse en el programa local de mejoramiento para desarrollar variedades resistentes. Un estudio se efectuó en Kabete, Kenia, durante tres ciclos consecutivos entre noviembre de 2011 y febrero de 2013. Se plantaron 36 genotipos de papa en un campo inoculado en el Instituto de Investigaciones Agrícolas de Kenia (KARI). En Kabete se usó un diseño de látice alfa con tres repeticiones. Los datos tomados fueron los días desde la siembra hasta el establecimiento del marchitamiento (DTOW), incidencia de la marchitez bacteriana (BWI), peso total de tubérculo (ton ha-1) (TTW), número total de tubérculos/ha (TTN), proporción de tubérculos de tamaño comercial (PWTTW), proporción de tubérculos sintomáticos con base en el peso (PSTTW), proporción de tubérculos sintomáticos con base en el número de tubérculos (PSTTN) e infección latente (LI) de los tubérculos. Casi todos los genotipos de papa evaluados en este estudio fueron susceptibles al marchitamiento bacteriano. La clasificación de los genotipos con base en la resistencia varió entre los tres ciclos de cultivo. En promedio, Los tres genotipos más resistentes fueron Kenya Karibu, Kenya Sifa, e Ingabire. El estudio identificó ocho genotipos de papa ((Meru, Ingabire, Kenya Karibu, Sherekea, Kihoro, Tigoni, Bishop Gitonga y Cangi) para usarse como progenitores prometedores para cruzas subsecuentes. Los genotipos seleccionados son prolíficos en producción de polen y se cultivan popularmente por los productores kenianos.

Climatic Change, Its Likely Impact on Potato ( Solanum tuberosum L.) Production in Kenya and Plausible Coping Measures

Potato is a cool season crop and plays an important role in Kenya’s economy. The crop is mostly grown under rain-fed conditions. However, most parts of Kenya are warming up in line with global trends and, information on how climate change will impact on potato production is presently lacking. An analysis of the literature in this area shows that changes in climate will lead to shifts in areas suitable for potato production, reduced yields and poorer quality of tubers for processing while demand for potato irrigation is also expected to increase. Distribution of pests (e.g. aphids, potato tuber moth and leaf miners) and diseases (e.g. late blight, bacterial wilt and viruses) are expected to increase since high temperatures allow more cycles of multiplication leading to greater pressure of pests and diseases. Seed potato produced under high vector pressure may degenerate fast due to viral infections. To remain competitive, the potato industry needs to embrace innovative strategies in adapting to climate change. New varieties adapted to extreme weather conditions (heat and drought tolerant) and possessing other desirable traits such as short dormancy, early maturity, pest resistance and/or tolerance will need to be developed. Investments will be required in irrigation infrastructure and in improved storage for both seed and ware potatoes since higher temperatures will most likely make it difficult to keep both seed and ware potatoes from season to season. Agronomic technologies that conserve soil moisture and lower soil temperatures will need to be adopted.