Taxonomy Of Peltaster, Trichomerium, And Related Genera Associated With Sooty Blotch And Flyspeck

Sooty blotch and flyspeck(SBFS) is a common disease complex caused by ectophytic fungi that occurs on a wide range of hosts in temperate and moist regions worldwide. SBFS fungi colonize on the surface of apple, pear, banana, and other fruits and blemish the appearance of hosts, which reduce the quality and commercial value of the fruits, resulting in economic losses. SBFS fungi show high diversity, comprising of over one hundred species in more than twenty genera. However, most of these SBFS fungi are putative species which are undescribed or taxonomically unresolved. The inadequate understanding in etiology has impeded the studies on biology, epidemiology or control of SBFS fungi.The object of this study is to resolve the taxonomic issues of some cryptic genera in SBFS fungi, such as Peltaster, Trichomerium, and related fungi by employing phylogenetic analyses combined with morphological comparison.Based on SBFS fungi isolates from nine provinces in China and dozens of different hosts, the taxonomy of Peltaster and Peltaster-like genera were investigated. Two novel genera, Neopeltaster and Pseudopeltaster were established within Dothideomycetes, Capnodiales, which are phylogenetically related to Peltaster. Based on morphology and phylogenetic analyses of internal transcribed spacer region(ITS), partial nuclear large subunit rDNA(nrLSU), partial mitochondrial small subunit rDNA(mrSSU), and partial translation elongation factor 1-α gene(EF), one new species was described in Neopeltaster, named N. mali, and three new speices in Peltaster were described, including Pe. crataegi, Pe. punctatum, and Pe. rosacearum, and Pe. fructicola was first reported from China. Morphological data and phylogenetic analyses of ITS-nrLSU revealed seven new speices in Pseudopeltaster, including Ps. ficus, Ps. fujianensis, Ps. cantonensis, Ps. gutianensis, Ps. hainanensis, Ps. heveae, and Ps. pruni.Based on the strains obtained from six provinces in China and five fungal collections abroad, we studied the taxonomy and phylogenetic relationships of Trichomerium and related genera. According to the morphological data and phylogenetic analyses of ITS-nrLSU, Alatosessilispora, Ordus, Tripospermum, and Trichomerium are taxonomically congruent. Trichomerium was used as the generic name, thus the other three are synonyms, and the generic concept was emended. Six new combinations were made, including T. bibrachiata, T. camelopardus, T. chiayiensis, T. infalcatum, T. myrti, and T. triramiferum. Six new species were described in Trichomerium: T. crataegi, T. dendrocalami, T. hunanensis, T. pruni, T. spiraea, and T. yunnanensis. Two new recorded species, T. camelopardus and T. dioscoreae were reported from China.Isolates in other genera causing SBFS were also identified and studied. Two new species were described: Ramichloridium crataegi and R. yanglingensis. Pseudoveronaea ellipsoidea and R. punctatum were newly recorded from China.Four Peltaster species were found from six different provinces. Pe. rosacearum was the most prevalent species, and frequently found from Middle and West China, such as Henan, Ningxia, Shaanxi, and Shanxi province; and it also had the widest host range, including apple, pear, howthron, and Rosa roxbunghii. Pe. punctatum had the widest regional distribution, and it spreaded from northeast region(e.g. Liaoning Province), over northwest region(e.g. Shaanxi Province), to midsouth region of China(e.g. Hunan Province), and the hosts included crabapple, hawthorn and plum. Whereas Pe. crataegi was only found on hawthorn fruit in Shaanxi Province. Pe. fructicola was newly recorded from China, which was found on crabapple and hawthorn in Liaoning and Shaanxi Province. The new SBFS genus, Pseudopeltaster included seven species, which distributed in South China with hot and humid climate and were isolated from plum, banana, traveller’s palm, and other tropical plants. Neopeltaster with the single species, N. mali, was only founded on crabapple in Liaoning Province. According to the result of pathogenicity tests, all speices excluded Pe. crataegi in these three genera could cause SBFS on apple fruit.Eight species in Trichomerium were found from Chongqing, Hubei, Hunan, Guangdong, Shaanxi, and Yunnan Province in China. T. camelopardus was the most prevalent species in this genus, accounting for 41% of the total strain number, and distributed through four different provinces. While other Trichomerium species were only occasionally found from restricted aeras. The result of pathogenicity tests showed that all species in Trichomerium could not form SBFS signs on apple fruit.