Colletotrichum species are plant pathogens, saprobes, and endophytes on a range of economically important hosts. However, the species occurring on pear remain largely unresolved. To determine the morphology, phylogeny and biology of Colletotrichum species associated with Pyrus plants, a total of 295 samples were collected from cultivated pear species (including P. pyrifolia, P. bretschneideri, and P. communis) from seven major pear-cultivation provinces in China. The pear leaves and fruits affected by anthracnose were sampled and subjected to fungus isolation, resulting in a total of 488 Colletotrichum isolates. Phylogenetic analyses based on six loci (ACT, TUB2, CAL, CHS-1, GAPDH, and ITS) coupled with morphology of 90 representative isolates revealed that they belong to 10 known Colletotrichum species, including C. aenigma, C. citricola, C. conoides, C. fioriniae, C. fructicola, C. gloeosporioides, C. karstii, C. plurivorum, C. siamense, C. wuxiense, and two novel species, described here as C. jinshuiense and C. pyrifoliae. Of these, C. fructicola was the most dominant, occurring on P. pyrifolia and P. bretschneideri in all surveyed provinces except in Shandong, where C. siamense was dominant. In contrast, only C. siamense and C. fioriniae were isolated from P. communis, with the former being dominant. In order to prove Koch's postulates, pathogenicity tests on pear leaves and fruits revealed a broad diversity in pathogenicity and aggressiveness among the species and isolates, of which C. citricola, C. jinshuiense, C. pyrifoliae, and C. conoides appeared to be organ-specific on either leaves or fruits. This study also represents the first reports of C. citricola, C. conoides, C. karstii, C. plurivorum, C. siamense, and C. wuxiense causing anthracnose on pear.

Species of Diaporthe (syn. Phomopsis) are important endophytes, saprobes and pathogens, infecting a wide range of plants and resulting in important crop diseases. However, the species occurring on pear remain largely unresolved. In this study, a total of 453 Diaporthe isolates were obtained from branches of Pyrus plants (including P. bretschneideri, P. communis, P. pyrifolia and P. ussuriensis collected from 12 provinces in China) showing shoot canker symptoms. Phylogenetic analyses based on five loci (ITS, TEF, CAL, HIS, and TUB) coupled with morphology of 113 representative isolates revealed that 19 Diaporthe species were isolated, representing 13 known species (including D. caryae, D. cercidis, D. citrichinensis, D. eres, D. fusicola, D. ganjae, D. hongkongensis, D. padina, D. pescicola, D. sojae, D. taoicola, D. unshiuensis and D. velutina) and six new species described here as D. acuta, D. chongqingensis, D. fulvicolor, D. parvae, D. spinosa and D. zaobaisu. Although Koch's postulates confirmed all species to be pathogenic, a high degree of variation in aggressiveness was observed. Moreover, these species have a high diversity, plasticity, and prevalence related to the geographical location and pear species involved.

Botryosphaeria dothidea is an important pathogenic fungus causing fruit rot, leaf and stem ring spots and dieback, stem canker, stem death or stool mortality, and decline of pear trees. Seven double-stranded RNAs (dsRNAs; dsRNAs 1 to 7 with sizes of 3,654, 2,773, 2,597, 2,574, 1,823, 1,623, and 511 bp, respectively) were identified in an isolate of B. dothidea exhibiting attenuated growth and virulence and a sectoring phenotype. Characterization of the dsRNAs revealed that they belong to two dsRNA mycoviruses. The four largest dsRNAs (dsRNAs 1 to 4) are the genomic components of a novel member of the family Chrysoviridae (tentatively designated Botryosphaeria dothidea chrysovirus 1 [BdCV1]), a view supported by the morphology of the virions and phylogenetic analysis of the putative RNA-dependent RNA polymerases (RdRps). Two other dsRNAs (dsRNAs 5 and 6) are the genomic components of a novel member of the family Partitiviridae (tentatively designated Botryosphaeria dothidea partitivirus 1 [BdPV1]), which is placed in a clade distinct from other established partitivirus genera on the basis of the phylogenetic analysis of its RdRp. The smallest dsRNA, dsRNA7, seems to be a noncoding satellite RNA of BdPV1 on the basis of the conservation of its terminal sequences in BdPV1 genomic segments and its cosegregation with BdPV1 after horizontal transmission. This is the first report of a chrysovirus and a partitivirus infecting B. dothidea and of a chrysovirus associated with the hypovirulence of a phytopathogenic fungus. IMPORTANCE Our studies identified and characterized two novel mycoviruses, Botryosphaeria dothidea chrysovirus 1 (BdCV1) and Botryosphaeria dothidea partitivirus 1 (BdPV1), associated with the hypovirulence of an important fungus pathogenic to fruit trees. This is the first report of a chrysovirus and a partitivirus infecting B. dothidea and of a chrysovirus associated with the hypovirulence of a phytopathogenic fungus. BdCV1 appears to be a good candidate for the biological control of the serious disease induced by B. dothidea . Additionally, BdPV1 is placed in a clade distinct from the established genera. The BdCV1 capsid has two major structural proteins, and the capsid is distinct from that made up by a single polypeptide of the typical chrysoviruses. BdPV1 is the second partitivirus in which the putative capsid protein shares no significant identity with any mycovirus protein. A small accompanying dsRNA that is presumed to be a noncoding satellite RNA of BdPV1 is the first of its kind reported for a partitivirus.

Species of Diaporthe infect a wide range of plants and live in vivo as endophytes, saprobes or pathogens. However, those in peach plants are poorly characterized. In this study, 52 Diaporthe strains were isolated from peach branches with buds, showing constriction canker symptoms. Phylogenetic analyses were conducted using five gene regions: internal transcribed spacer of the ribosomal DNA (ITS), translation elongation factor 1-α (TEF), ß-tubulin (TUB), histone (HIS), and calmodulin (CAL). These results coupled with morphology revealed seven species of Diaporthe, including five known species (D. caryae, D. cercidis, D. eres, D. hongkongensis, and D. unshiuensis). In addition, two novel species D. jinxiu and D. zaofenghuang are introduced. Except for the previously reported D. eres, this study represents the first characterization of Diaporthe species associated with peach constriction canker in China, and contributes useful data for practicable disease management.