Alternaria Nees, Syst. Pilze (Würzburg): 72 (1817).
Pathogenic on host. Sexual morph: Ascomata small, solitary to clustered, erumpent to (nearly) superficial at maturity, globose to ovoid, dark brown, smooth, apically papillate, ostiolate. Ostiole papilla short, blunt. Peridium relatively thin. Hamathecium of cellular pseudoparaphyses. Asci (4–6–) 8- spored, bitunicate, fissitunicate, cylindrical to cylindroclavate, straight or somewhat curved, with a short, furcate pedicel and minute ocular chamber. Ascospores ellipsoid to fusoid, muriform, slightly constricted at septa, yellow-brown, without guttules, smooth-walled. Asexual morph: Stroma rarely formed, setae and hyphopodia absent. Conidiophores macronematous, mononematous, simple or irregularly and loosely branched, pale brown or brown, solitary or in fascicles. Conidiogenous cells integrated, terminal becoming intercalary, polytretic, sympodial, or sometimes monotretic, cicatrized. Conidia catenate or solitary, dry, ovoid, obovoid, cylindrical, narrowly ellipsoid or obclavate, beaked or nonbeaked, pale or medium olivaceous-brown to brown, smooth or verrucose, with transverse and with or without oblique or longitudinal septa (Adapted from Woudenberg et al. 2013 and Ariyawansa et al. 2015).
Type species: Alternaria tenuis Nees
Notes: Alternaria was introduced by Nees (1816) with A. tenuis as type species. Alternaria is characterized by solitary to clustered, erumpent to superficial ascomata, cylindrical to cylindroclavate asci and ellipsoid to fusoid, muriform ascospores. In the phylogenetic analyses of Woudenberg et al. (2013) based on SSU, LSU, ITS, GAPDH, RPB2 and TEF1 revealed that multiple paraphyletic genera exist within the Alternaria complex and several clades do not relate to the species-groups based on morphological characters. Woudenberg et al. (2013) also synonymized several genera such as Allewia, Brachycladium, Chalastospora, Chmelia, Crivellia, Embellisia, Lewia, Nimbya, Sinomyces, Teretispora, Ulocladium, Undifilum and Ybotromyces under Alternaria senso stricto. This treatment was followed by consequent authors (Ariyawansa et al. 2015; Li et al. 2022). Ariyawansa et al. (2015) described the sexual morph of Alternaria alternata from Italy and added a new species A. murispora but did not obtain the asexual morph from cultures and provided a phylogenetic tree of Alternaria based on ITS, SSU, LSU and RPB2 sequence data. Li et al. (2022) discussed the species limits, evolution and provided an updated mutigene phylogeny, and taxonomic explanation on the classification Alternaria. Several authors added new species to Alternaria (Zhang et al. 2003; Shen et al. 2007; Simmons and Hill 2007; Marin-Felix et al. 2019). Alternaria is a distinct but complex genus in Pleosporaceae. Molecular markers available for Alternaria include ITS, LSU, SSU, TEF1, RPB2, GADPH and Alt-a1 genes.