Influence of Genotype, Location and Plant Age on Incidence and Severity of Cassava Mosaic and Cassava Brown Streak Diseases in Western Kenya

Abstract

This study aimed to assess elite cassava genotypes for resistance to cassava mosaic and brown streak diseases at Alupe, Kakamega and Kibos in Western Kenya. The trial was conducted using alpha lattice balanced design using 24 genotypes with three replicates, for an extended cropping cycle between 2016 and 2017. Results for combined analysis of variance showed that genotype, location, month after planting (MAP) and their interactions significantly influenced (P ≤ 0.05) incidence and severity of CMD and CBSD. High CMD incidence and severity was recorded across all cassava genotypes at Alupe (mean 0.730; 1.256) as opposed to Kakamega (mean 0.000; 1.000) and Kibos (mean 0.031; 1.006). Similarly, CBSD root incidence and severity were high in Alupe (mean 0.848; 1.310), as opposed to Kakamega (mean 0.020; 1.006) and Kibos (mean 0.188; 1.078). Within location analysis for CMD and CBSD incidence and severity among cassava genotypes 12 MAP gave varied results. Genotypes Kibandameno and Kalawe had the highest CMD and CBSD incidence and severity in all three locations. Whiteflies abundance was significantly influenced (P ≤ 0.05) by genotype, location, MAP time and interaction. Significant interaction (P ≤ 0.05) between all disease resistance traits further confirmed dual resistance amongst the cassava genotypes, however, this was location specific and not generalized. These findings should be of value to cassava breeding and development efforts throughout Kenya, and other parts of sub Saharan Africa affected or threatened by CMD and CBSD and will hopefully contribute to the development of much improved and/or resistant genotypes and, ultimately more effective management of two of Africa's most pernicious threats to food security