Plenodomus dezfulensis sp. nov. causing leaf spot of Rapeseed in Iran

Abstract

Rapeseed (Brassica napus subsp. napus) is one of the autumn crops in Iran. A new fungal species isolated from internal tissues associating a typical leaf spot of Rapeseed in Dezful (southwestern Iran) was described and illustrated. The sampling and isolation were performed in the late fall of 2019 (during December), which led to obtain the colonies with the similar morphology. Molecular phylogenetic analyses based on a combined matrix of the internal transcribed spacer regions 1 and 2 including the intervening 5.8S nuclear ribosomal DNA (ITS), and partial regions of the β-tubulin (tub2) and RNA polymerase II second largest subunit (rpb2) indicated that two isolated strains represent a new Plenodomus species in family Leptosphaeriaceae (Pleosporales). These novel strains formed a sister lineage with P. biglobosus in our phylogenetic analyses, while, observed morphology is distinguished the taxa from P. biglobosus by its pycnidia in having hyphal outgrowths and lacking cylindrical neck. Accordingly, P. dezfulensis sp. nov. was introduced and its pathogenicity was investigated. Pathogenicity test with both P. dezfulensis strains on three-week seedlings of Rapeseed reproduced leaf spot symptoms. These results approve P. dezfulensis as the causal agent of leaf spot observed on Rapeseed in Dezful.