The Putative Effector Protein AlPE1 From Ascochyta lentis Causes Necrosis in Lentil and Pea

Ascochyta blight of lentil is caused by the hemibiotrophic fungal pathogen species Ascochyta lentis . Recent advances in whole genome sequencing have led to the availability of many fungal genome assemblies, enabling comparison of isolates that can lead to the identification of virulence genes or effectors. Here, we compare genome assemblies for the reference A. lentis isolate Al4 and the isolate Al Kewell and identify a single gene named AlPE1 ( A. lentis putative effector 1) that is present in Al4 but absent from Al Kewell. In Al4, AlPE1 is located in the middle of a 175‐kbp AT‐rich region and encodes a secreted protein with a mature protein molecular weight of 5.5 kDa. The polypeptide has eight cysteine residues and is predicted to be an apoplastic effector by EffectorP. Homologues of AlPE1 are found in other plant pathogenic fungi including Parastagonospora , Bipolaris and the closely related Ascochyta species that affect legumes. AlPE1 is expressed in planta with levels increasing at the mid‐infection stage in three lentil cultivars, where disease progression transitions to necrotrophy. We used agroinfiltration to test the function of transiently expressed AlPE1 protein in lentil and pea leaves, and after 5 days, weak necrosis was detected in both species. AlPE1 is proposed as a necrosis‐inducing effector that may contribute to ascochyta blight in lentil.