Variability Pattern for Resistance to Purple Blotch (Alternaria porri ) Disease of Onions (Allium cepa L.) in North Western Nigeria

Abstract

Five onion cultivars Red Creole, Kaharda, Koumassa, Sokoto local and ori were selected on the basis of diverse genetic backgrounds with respect to resistance to Alternaria porri (Ellis.) Cif. The cultivars were crossed in a complete diallel, the 25 F1s generated and their parents were evaluated in replicated yield trials at Sokoto in Sokoto State and Talata Mafara in Zamfara State, Nigeria, during the 2004/2005 and 2005/2006 dry seasons. The experiments were laid out in a randomised complete block design (RCBD) with three replications. Analysis of the variance component for the combined seasons and locations indicate that genotypic variance was greater than the environmental variance for all characters under  consideration with exception of bulb weight. Disease incidence recorded 31.20%, 30.58% and 5.42% as phenotypic, genotypic and environmental coefficients of variability. Disease severity recorded 34.96%, 32.84% and 11.00% as phenotypic, genotypic and environmental coefficients of variability. With respect to fresh bulb yield 94.90%, 93.53% and 15.78% were observed as phenotypic, genotypic and environmental coefficients of variability for the genotypes. Cured bulb yield recorded 103.47%, 102.27% and 14.96% respectively as phenotypic, genotypic and environmental coefficients of variability. Similarly 29.43%, 24.79% and 17.91% were observed for days to maturity, as phenotypic, genotypic and environmental coefficients of variability. Variability was found to exist among the genotypes for the various characters they were evaluated for.

Keywords: Variability, Resistance, Purple Blotch, Disease, Onions