Pathogenic variation and virulence related responses of Ascochyta lentis on lentil

Abstract

Ascochyta blight of lentil (Lens culinaris ssp. culinaris) is caused by Ascochyta lentis. The disease causes severe damage to all aerial parts of the plant and may lead to total crop loss during extremely severe epidemics. To identify qualitative differences in resistance within Australian lentil crops, variation in virulence was examined among 17 isolates of A. lentis on six differential lentil genotypes (ILL7537, ILL5588 (cv. Northfield), ILL6002, ILL5722 (cv. Digger), ILL481 (cv. Indianhead) and CIPA203 (cv. Nipper)). Six distinct virulence patterns were identified, with Pathotype I (AL4) being highly virulent, causing disease on all genotypes except ILL7537 and pathotype VI (Kewell) exhibiting low virulence on all genotypes. Histopathology studies were carried out to further understand interaction differences between isolate-host combinations and add to the knowledge of possible resistance mechanisms underlying lentil’s defence to the pathogen. The infection process was compared between lentil genotypes with different levels of resistance and isolates with different levels of virulence. Microscopic and biochemical differences were observed between compatible and incompatible interactions, which were related to time-after-inoculation, with slower responses noted in susceptible lentil genotypes. Relatively fast release of reactive oxygen species (ROS) and a subsequent hypersensitive response (HR) was central to initial defence at the point of penetration in the most resistant lentil genotypes.