ARS | Publication request: TWO PATHOTYPES OF THE CHICKPEA PATHOGEN ASCOCHYTA RABIEI IDENTIFIED IN THE UNITED STATES.

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: June 30, 2005
Publication Date: N/A

Technical Abstract: Ascochyta blight of chickpea caused by Ascochyta rabiei is a serious disease in many parts of the world. Considerable pathogenic variation among isolates of the pathogen has been reported. In order to understand the pathogenic variation in the US, a defined pathogenicity assay, a mini-dome technique, was developed to determine virulence variation among isolates of the pathogen. Based on different distribution patterns of chickpea response to virulence, isolates of A. rabiei were separated into two pathotypes. Pathotype I isolates caused a bimodal response among chickpea genotypes, whereas pathotype II isolates caused continuous response to virulence among chickpea genotypes. The different response patterns suggest different resistance mechanisms of chickpea to the two pathotypes, and likewise the two pathotypes may possess different pathogenic mechanisms. The separation of the two pathotypes may help elucidate the mechanistic interactions between chickpea and Ascochyta rabiei. Isolates collected from various regions of the United States over many years were assayed for virulence using the mini-dome bioassay. All the isolates could be classified either as pathotype I or pathotype II. More interestingly, most of the isolates collected from the early years belonged to pathotype I, whereas most of the contemporary isolates belonged to pathotype II, suggesting adaptation of the A. rabiei population to the cultivation of resistant cultivars in the United States.