Phylogeny and morphology of Leptosphaerulina saccharicola sp nov and Pleosphaerulina oryzae and relationships with Pithomyces

A Dothideomycete species, associated with leaf spots of sugarcane (Saccharum officinarum), was collected from Nakhonratchasima Province, Thailand. A single ascospore isolate was obtained and formed the asexual morph in culture. ITS, LSU, RPB2 and TEF1 alpha gene regions were sequenced and analyzed with molecular data from related taxa. In a phylogenetic analysis the new isolate clustered with Leptosphaendina americana, L. arachidicola, L. australis and L. trifolii (Didymellaceae) and the morphology was also comparable with Leptosphaerulina species. Leptosphaertdina saccharicola is introduced to accommodate this new collection which is morphologically and phylogenetically distinct from other species of Leptosphaerulina. A detailed description and illustration is provided for the new species, which is compared with similar taxa. The type specimen of Pleosphaerulina oryzae, is transferred to Leptosphaerulina. It is redescribed and is a distinct species from L. australis, with which it was formerly synonymized. Leptosphaerulina species have been linked to Pithomyces but the lack of phylogenetic support for this link is discussed. The character of the asexual morph of Leptosphaerulina, which is similar to Pithomyces, may to have evolved on separate occasions.