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Spikelet rot disease (SRD) is an emerging disease of the grain surface of naked oat in China that affects both grain yield and quality. The typical symptom is discoloration from the black structures of the causal fungi. Here, we investigated the fungal communities on the grain surfaces of cultivar Bayou 13 grown in ten ecological oat-producing regions of China, to identify the main pathogens of naked oat SRD. Our results showed that the growth of Alternaria spp. and Davidiella spp. exhibited a competitive relationship and was mainly affected by the elevations of all 10 ecological regions. The dominant pathogens were Davidiella spp. in Shannan Prefecture in Tibet and Haidong Prefecture in Qinghai Province and Alternaria spp. in the other eight regions. The ratios of black pathogens of interest to all pathogens in Shannan Prefecture and Haidong Prefecture were significantly lower than those of the other eight regions, thus indicating that SRD mainly occurred in regions below 2000 m (elevation). We isolated black fungal pathogens from grain surfaces and deduced that they were Alternaria spp. by sequence comparison. The blackened appearance of the grain surfaces was more evident under spray inoculation with a spore suspension of Alternaria than under the control in greenhouse experiments. The recovered pathogen was the same as the pathogen used for inoculation. We thus concluded that Alternaria alone causes naked oat SRD and mainly infects naked oat in regions below 2000 m, which provides a basis for the recognition and management of SRD of naked oat.

A morphologically distinct isolate of Cladosporium sphaerospermum from a North American patent collection, referenced as Cladosporium lignicola in the patent, was examined. Generic affinity was confirmed by scanning electron microscopic examination of conidiogenous loci and conidial hila. Species identity as C. sphaerospermum was indicated by DNA sequence data derived from actin and translation elongation factor 1-alpha genes, and the internal transcribed spacer region. The isolate broadens the morphological limits of C. sphaerospermum by production of obclavate, occasionally transversely septate conidia with subrostrate conidiogenous apices ('alternarioid' conidia), and by production of conidia larger than those in prior standard descriptions. Type material of C. lignicola was re-examined and compared with the North American fungus, from which it is morphologically distinct. The decision to reduce C. lignicola to synonymy under C. herbarum was confirmed.

The genus Cladosporium is restricted to dematiaceous hyphomycetes with a coronate scar type, and Davidiella teleomorphs. In the present study numerous cladosporium-like taxa are treated, and allocated to different genera based on their morphology and DNA phylogeny derived from the LSU nrRNA gene. Several species are introduced in new genera such as Hyalodendriella, Ochrocladosporium, Rachicladosporium, Rhizocladosporium, Toxicocladosporium and Verrucocladosporium. A further new taxon is described in Devriesia (Teratosphaeriaceae). Furthermore, Cladosporium castellanii, the etiological agent of tinea nigra in humans, is confirmed as synonym of Stenella araguata, while the type species of Stenella is shown to be linked to the Teratosphaeriaceae (Capnodiales), and not the Mycosphaerellaceae as formerly presumed.Taxonomic novelties: Devriesia americana Crous & Dugan, sp. nov., Hyalodendriella Crous, gen. nov., Hyalodendriella betulae Crous sp. nov., Ochrocladosporium Crous & U. Braun, gen. nov., Ochrocladosporium elatum (Harz) Crous & U. Braun, comb. nov., Ochrocladosporium frigidarii Crous & U. Braun, sp. nov., Rachicladosporium Crous, U. Braun & Hill, gen. nov., Rachicladosporium luculiae Crous, U. Braun & Hill, sp. nov., Rhizocladosporium Crous & U. Braun, gen. nov., Rhizocladosporium argillaceum (Minoura) Crous & U. Braun, comb. nov., Toxicocladosporium Crous & U. Braun, gen. nov., Toxicocladosporium irritans Crous & U. Braun, sp. nov., Verrucocladosporium K. Schub., Aptroot & Crous, gen. nov., Verrucocladosporium dirinae K. Schub., Aptroot & Crous, sp. nov.

The Cladosporium herbarum complex comprises five species for which Davidiella teleomorphs are known. Cladosporium herbarum s. str. (D. tassiana), C. macrocarpum (D. macrocarpa) and C. bruhnei (D. allicina) are distinguishable by having conidia of different width, and by teleomorph characters. Davidiella variabile is introduced as teleomorph of C. variabile, a homothallic species occurring on Spinacia, and D. macrospora is known to be the teleomorph of C. iridis on Iris spp. The C. herbarum complex combines low molecular distance with a high degree of clonal or inbreeding diversity. Entities differ from each other by multilocus sequence data and by phenetic differences, and thus can be interpreted to represent individual taxa. Isolates of the C. herbarum complex that were formerly associated with opportunistic human infections, cluster with C. bruhnei. Several species are newly described from hypersaline water, namely C. ramotenellum, C. tenellum, C. subinflatum, and C. herbaroides. Cladosporium pseudiridis collected from Iris sp. in New Zealand, is also a member of this species complex and shown to be distinct from C. iridis that occurs on this host elsewhere in the world. A further new species from New Zealand is C. sinuosum on Fuchsia excorticata. Cladosporium antarcticum is newly described from a lichen, Caloplaca regalis, collected in Antarctica, and C. subtilissimum from grape berries in the U.S.A., while the new combination C. ossifragi, the oldest valid name of the Cladosporium known from Narthecium in Europe, is proposed. Standard protocols and media are herewith proposed to facilitate future morphological examination of Cladosporium spp. in culture, and neotypes or epitypes are proposed for all species treated.Taxonomic novelties: Cladosporium antarcticum K. Schub., Crous & U. Braun, sp. nov., C. herbaroides K. Schub., Zalar, Crous & U. Braun, sp. nov., C. ossifragi (Rostr.) U. Braun & K. Schub., comb. nov., C. pseudiridis K. Schub., C.F. Hill, Crous& U. Braun, sp. nov., C. ramotenellum K. Schub., Zalar, Crous& U. Braun, sp. nov., C. sinuosum K. Schub., C.F. Hill, Crous& U. Braun, sp. nov., C. subinflatum K. Schub., Zalar, Crous& U. Braun, sp. nov., C. subtilissimum K. Schub., Dugan, Crous& U. Braun, sp. nov., C. tenellum K. Schub., Zalar, Crous & U. Braun sp. nov., Davidiella macrocarpa Crous, K. Schub. & U. Braun, sp. nov., D. variabile Crous, K. Schub. & U. Braun, sp. nov.