Morphological and phylogenetic analyses reveal two new Alternaria species (Pleosporales, Pleosporaceae) in Alternaria section from Cucurbitaceae plants in China

Abstract

Alternaria species are commonly found as saprophytes, endophytes and plant pathogens. During a survey of small-spored Alternaria in China, two new species were discovered from Cucurbitaceae plants collected in Hubei and Sichuan provinces. This study identified two new species of Alternaria using seven genes (ITS, GAPDH, TEF1, RPB2, Alt a 1, EndoPG, and OPA10-2) for phylogenetic analyses and morphological characteristics. The two new species A. jingzhouensis and A. momordicae were described and illustrated. Alternaria jingzhouensis sp. nov., associated with Citrullus lanatus, is characterized by producing muriform, ellipsoidal, flask-shaped, rostrate, and beaked conidia. It differs from A. koreana, A. ovoidea, and A. baoshanensis by bearing conidia in a simple conidiogenous locus with occasionally longer beaks in a chain, and from A. momordicae sp. nov. by having shorter beaks. Alternaria momordicae sp. nov. from Momordica charantia was distinct from A. koreana, A. ovoidea, and A. baoshanensis by producing muriform, long ellipsoid or ovoid to obclavate, sometimes inverted club-shaped conidia on a single conidiogenous locus with a wider body and longer beak in a chain, and distinct from A. jingzhouensis sp. nov. by a longer beak conidia. These two species were clearly distinguished from other species in the section Alternaria based on DNA based phylogeny and morphological characteristics. The morphological features were discussed and compared to relevant species in the present paper.