Abstract
Alternaria section Nimbya, currently contains six species which are pathogens of members of the Juncaceae and Cyperaceae plant families. The prominent morphological character in the members of this section is internal compartmentation of conidia into conspicuous angular lumina interconnected by narrow channels through the transverse distosepta and fewer transverse eusepta. In the study on fungi from culm lesions of Carex sp. (Cyperaceae) from West Azarbaijan province, Iran, four isolates with typical characteristics of Alternaria were isolated and studied taxonomically. Based on combination of morphological characters and molecular phylogeny based on ITS–rDNA and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene sequences, the isolates represent a new undescribed species of Alternaria in the section Nimbya, which is described here as Alternaria caricicola sp. nov. The new species is characterized by straight to slightly curved obclavate conidia with 6–14 transverse distosepta, 1–4 darkened eusepta, and an unbranched, tapering apical beak. A detailed description and illustrations are provided and compared with similar taxa in the section Nimbya.