Evaluation of Selected Cassava (Manihot esculenta Crantz) Cultivars Grown in Kenya for Resistance to Bacterial Blight Disease

Abstract

Bacterial blight of cassava is one of the most important diseases of cassava worldwide due to its growing concern, widespread and destructive nature. Even though the use of resistant cultivars is the most effective management strategy for the disease, such cultivars are not well identified. Therefore, the objective of this study was to screen 21 cassava cultivars collected from major growing regions of Kenya, for reaction against bacterial blight caused by Xanthomonas axonopodis pv. manihotis (Xam). The cultivars were inoculated with Xam by leaf clipping and stem puncturing inoculation methods, for in vitro and potted plants, respectively. The cassava cultivars varied in their reaction to the pathogen, including incubation period, wilt incidence and area under the disease progress curve (AUDPC) values. Four groups of cultivars with differential reactions to Xam isolate were identified. Four cultivars (TME419, 30572, 98/0505 and Kibaha) were resistant, 4 cultivars (Albert, Ebwanatereka, Karibuni and 92/0326) moderately resistance, 11 cultivars (Serere, Muzege, TME7, 98/0581, Tajirika, Namikonga, Kibandameno, Mzalauka, AR40-6, Shibe and 01/1371) susceptible and the other 2 cultivars (Kiroba and Numbari) were highly susceptible. The resistant cultivars should be multiplied and made available as clean planting materials to cassava producing farmers and integrated as one of the options in disease management measures. These genotypes could also form vital germplasm of cassava bacterial blight disease resistance breeding programs. The cassava cultivars that showed a resistant reaction to the bacterial blight pathogen should be further evaluated against a large number of Xam isolates.