Variation in pathogenicity of Ascochyta rabiei on chickpeas

Abstract

Studies of the geographic variability of Ascochyta rabiei were done using chickpea cultivars of differing susceptibility under uniform growth room conditions. The pathogenicity of certain isolates particularly those from the Indian subcontinent and Western Asia was greater than that of most isolates collected in the Western Mediterranean. Several cultivars already deployed in breeding programmes showed stable resistance to the fungus, others with intermediate levels of resistance were less stable when exposed to a high disease pressure developed by the repeated passaging of isolates through them. In general differences in pathogenicity were attributed to variations in aggressiveness shown by the constant ranking of the cultivars used. Sporulation may not be linked to pathogenicity and significant statistical interactions with reversals in cultivar rankings suggests this to be an area for further study. Resistance to A. rabiei seems to be polygenic or at least oligogenic. In conditions of prolonged disease pressure some barriers to infection and/or spoulation may be overcome by pathogenic adaptation.

Keywords:

• Chickpea
• Ascochyta
• blight
• resistance