ماتیو ابنگ

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.

Microsatellites have become markers of choice for molecular mapping and marker assisted selection of key traits such as disease resistance in many crop species. The aim of this study was to construct a genetic linkage map and analyze quantitative trait loci (QTLs) for leaf size and ascochyta blight resistance in chickpea (Cicer arietinum L.), as well as quantify the contribution of each QTL to observed phenotypic variation. Fifty-eight SSR markers and one morphological marker (flower color) were mapped on 83 F2 individuals and F2:3 families derived from the cross ICC 12004 (resistant) ´ Bivanij (susceptible local cultivar) at the International Center for Agricultural Research at Dry Area (ICARDA). The linkage map comprised eight linkage groups, excluding flower color which didnt assign to any linkage group. Area under disease progress curve (AUDPC) was used to evaluate the F2 population and F3 families. A fain's test based on means and variances of the ascochyta blight reaction of F3 families showed that a few genes segregated in the population. Using composite interval mapping, one and three genomic regions were detected, which were in association with leaf size and reaction to ascochyta blight, respectively. One QTL on LG7 accounted for 15% of phenotypic variation for leaf size. Furthermore, three QTLs on LG3, LG4 and LG6 accounted for 46.5% of the total estimated phenotypic variation for reaction to ascochyta blight. Fine mapping of the QTLs identified in this study would lead to the identification of markers that could be used for marker-assisted selection of chickpea genotypes with resistance to acochyta blight. These findings are particular pertinent considering that we used Ascochyta rabiei pathotype III and ICC 12004 (resistant to pathotype III) for the first time.