Impact of pathotypes and spore concentrations on Ascochyta blight incidence in two chickpea (Cicer arietinum L.) genotypes

Ascochyta blight (AB) is the major constraint and the most destructive disease for chickpea production in Central and West Asia and North Africa (CWANA) region. To study response of chickpea genotypes against this disease, a research was conducted in the International Center for Agricultural Research in the Dry Areas (ICARDA) in 2007. Effects of four pathotypes of A. rabiei in three spore concentrations were investigated on disease score (DS) and leaf infection percentage (LI) of two genotypes of chickpea (Iranian local "Bivanij" and ICC12004), using systematic and mini-dome methods. The layout of this study was factorial experiment based on completely randomized design with three replications. Results revealed significant differences between genotypes, isolates and concentrations for DS and LI. New variant of pathotype IV developed highest pathogenicity on both genotypes. Lower coefficient of variation in the second method confirmed higher precision of mini-dome trial. There was significant correlation between LI and DS. Disease score for Bivanij (susceptible to AB) were 3.5 and 4.0 under 2×103 spores.ml-1 concentration which suggested presence of some minor Ascochyta blight resistance genes in this genotype. Effect of spore concentration was divided into linear and quadratic components. Disease severity increased significantly with the increase in spore concentration and this trend was linear. Both genotypes were susceptible to pathotype IV, whereas only IC 12004 was resistant to other pathotypes. The highest spore concentration (2×105 spores.ml-1) developed the most discrimination between two chickpea genotypes.