Trichoderma is known worldwide as biocontrol agents of plant diseases, producers of enzymes and antibiotics, and competitive contaminants of edible fungi. In this investigation of contaminated substrates of edible fungi from North China, 39 strains belonging to 10 Trichoderma species isolated from four kinds of edible fungi were obtained, and three novel species belonging to the Harzianum clade were isolated from the contaminated substrates of Auricularia heimuer and Pholiota adipose. They were recognized based on integrated studies of phenotypic features, culture characteristics, and molecular analyses of RNA polymerase II subunit B and translation elongation factor 1-α genes. Trichoderma auriculariae was strongly supported as a separate lineage and differed from T. vermifimicola due to its larger conidia. Trichoderma miyunense was closely related to T. ganodermatigerum but differed due to its smaller conidia and higher optimum mycelial growth temperature. As a separate lineage, T. pholiotae was distinct from T. guizhouense and T. pseudoasiaticum due to its higher optimum mycelial growth temperature and larger conidia. This study extends the understanding of Trichoderma spp. contaminating substrates of edible fungi and updates knowledge of species diversity in the group.

Camellia chrysantha (Hu) Tuyama, belonging to the Theaceae family, is famous for its large size and golden yellow flowers, which has high ornamental and health care functions (Mo et al. 2013). Anthracnose is one of the most important fungal diseases worldwide, causing serious economic losses to many plants. In October 2019, severe anthracnose symptoms were observed on the leaves of C. chrysantha in a 0.6 hectare field with 15-20% disease incidence in Fangchenggang city, Guangxi Zhuang Autonomous Region of China. Diseased leaves initially appeared irregular chlorotic spots, which afterwards enlarged and coalesced. Finally, the spots became dark brown or black, sunken lesions (8-22 mm in diameter), and covered with plenty of acervuli. For pathogen isolation, the leaf lesions were cut into small tissue pieces (5 mm×5 mm), disinfected by 0.3% sodium hypochlorite for 2 min and 70% ethanol for 40 s, rinsed in sterile distilled water, and then incubated at 28°C on potato dextrose agar (PDA) plates. A total of 7 fungal isolates with whitish to light grey, dense colonies were recovered at 5 days. These isolates were tentatively identified as belonging to Colletotrichum gloeosporioides species complex through morphological and cultural characters (Weir et al. 2012). The conidia were nonseptate, cylindrical with obtuse to rounded ends, 13.9 to 18.3 (average 16.1) μm × 4.5 to 6.2 (average 5.4) μm (n = 50). For further precise identification, the 7 Colletotrichum isolates were analyzed using partial sequences of genomic loci including the internal transcribed spacer (ITS), β-tubulin (TUB), calmodulin (CAL), actin (ACT), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), glutamine synthetase (GS), and the mating type locus MAT1-2 (ApMat) genes (Liu et al. 2015). The amplification sequences were compared with the sequences registered in the GenBank database based on nucleotide similarity. The above sequences of 4 isolates (JZB-PF4232, JZB-PF2231, JZB-PF42 and JZB-PF22) had 99-100% identity to the sequences of Colletotrichum siamense strains retrieved from GenBank, while the sequences of the other 3 isolates (JZB-PF3231, JZB-PF32 and JZB-PF41) showed over 99% identity with those of the C. fructicola strains. All the sequences were deposited in GenBank with accession number MT708987 to MT709007, MW149430 to MW149433, and MW142259 to MW142282. A multi-loci phylogenetic analysis of the concatenated sequences of ITS, TUB, CAL, ACT, GAPDH, GS and ApMat genes placed the 4 isolates described above in the C. siamense clade, while the other 3 isolates was attribute to the C. fructicola clade. Pathogenicity tests were conducted on 7 healthy 2-year-old C. chrysantha seedlings (cv. Fangpu), consisted of 21 wounded leaves made by a sterile needle, with 3 leaves per seedling. Artificial inoculations were performed by treating each seedling with 20 µl of spore suspension (106 conidia/ml) of each isolate. Leaves of seedlings treated with sterilized water under the same conditions served as controls. The experiment was repeated three times. All the seedlings were covered with plastic bags to maintain high humidity (90% RH) and placed in a greenhouse kept at 25°C with a 16 h light / 8 h dark photoperiod. After 8 days, the inoculated leaves of C. chrysantha plants developed typical dark brown or black lesions, similar to the symptoms in the field, whereas controls remained symptomless. Koch's postulates were fulfilled by re-isolation of the same fungi from symptomatic inoculated leaves, identification confirmed by morphological and molecular characteristics, respectively. C. siamense and C. fructicola have been found to cause anthracnose on Camellia sinensis (Wang et al. 2016; Shi et al. 2018). C. fructicola has also been reported to cause anthracnose on Citrus sinensis in China (Hu et al. 2019). To our knowledge, this is the first report of C. siamense and C. fructicola causing anthracnose on C. chrysantha in China.

Potato leaves with symptoms of foliar diseases were collected from eight different geographical areas in southern China. A total of 109 Alternaria isolates were recovered and identified to three species according to morphological characteristics, nucleotide sequencing and PCR-RFLP analysis. Three Alternaria species were recovered, of which A. tenuissima was the most common, followed by A. alternata and A. solani. Pathogenicity tests indicated that all species caused foliar symptoms on potato cultivar ‘Favorite’. Compared with earlier results reported in 2010–2013 in northern China, the proportion of A. alternata isolates was notably increased, while the number of A. solani isolates was lower. This study provides a survey of the Alternaria species composition associated with potato foliar diseases in southern China.

This study explored the role of viable cells and active metabolites in the seed-coating preparations of living Streptomyces globisporus in plant growth promotion and disease control against Verticillium wilt of cotton. Pot experiments were carried out to evaluate the effects of seed coating with living (LA), inactivated (IA), and 10-fold diluted living (DLA) preparations of S. globisporus Act7 and Act28 on plant growth performance and disease index of cotton seedlings under attack by Verticillium dahliae. Compared with the control, leaf greenness was increased by 50.0–70.1% across all the three treatments of Act7 (LA7, IA7, and DLA7), and the leaf area of LA7- and DLA7-treated seedlings was increased by more than twice (p < 0.05). DLA7 also increased shoot weight by 62.2%, while IA7 and DLA7 improved plant biomass by 30.4% and 72.1%, respectively (p < 0.05). The root vitality of IA7- and DLA7-treated seedlings was enhanced by 69.1% and 75.8%, respectively. The disease index of Verticillium wilt was reduced by 31.9% (LA7), 25.0% (IA7), and 66.7% (DLA7) after treatments. The effects of Act28 preparations were similar to those of Act7 preparations. Through the combined action of viable spores and active metabolites, seed coating with an appropriate dose of living S. globisporusan can considerably promote plant growth and improve root vitality, while reducing the incidence of Verticillium wilt in cotton seedlings under attack by V. dahliae.

Introduction: Verticillium wilt is the most devastating soil-borne disease affecting Cotinus coggygria in the progress of urban landscape construction in China.Methods: To assess the variability of the rhizosphere-associated soil microbiome in response to Verticillium wilt occurrence, we investigated the microbial diversity, taxonomic composition, biomarker species, and co-occurrence network of the rhizosphere-associated soil in Verticillium wilt-affected C. coggygria using Illumina sequencing.Results: The alpha diversity indices of the rhizosphere bacteria in Verticillium wilt-affected plants showed no significant variability compared with those in healthy plants, except for a moderate increase in the Shannon and Invsimpson indices, while the fungal alpha diversity indices were significantly decreased. The abundance of certain dominant or crucial microbial taxa, such as Arthrobacter, Bacillus, Streptomyces, and Trichoderma, displayed significant variations among different soil samples. The bacterial and fungal community structures exhibited distinct variability, as evidenced by the Bray–Curtis dissimilarity matrices. Co-occurrence networks unveiled intricate interactions within the microbial community of Verticillium wilt-affected C. coggygria, with greater edge numbers and higher network density. The phenomenon was more evident in the fungal community, showing increased positive interaction, which may be associated with the aggravation of Verticillium wilt with the aid of Fusarium. The proportions of bacteria involved in membrane transport and second metabolite biosynthesis functions were significantly enriched in the diseased rhizosphere soil samples.Discussion: These findings suggested that healthy C. coggygria harbored an obviously higher abundance of beneficial microbial consortia, such as Bacillus, while Verticillium wilt-affected plants may recruit antagonistic members such as Streptomyces in response to Verticillium dahliae infection. This study provides a theoretical basis for understanding the soil micro-ecological mechanism of Verticillium wilt occurrence, which may be helpful in the prevention and control of the disease in C. coggygria from the microbiome perspective.

Camellia chrysantha (Hu) Tuyama (golden camellia) is an important ornamental and medicinal plant grown in southern China, which is often referred to as “the queen of camellia” (Zhang et al. 2017). ...