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Abstract Background Plant phyllosphere microbes are important for the host plant's protection. Plant growth‐promoting rhizobacteria (PGPR) and Trichoderma are common biocontrol agents (BCAs) for disease management. Pathogens and BCAs can change the rhizosphere microbial composition; however, the effect of PGPR or Trichoderma on plant phyllosphere microbes, particularly for mesocosms involving the interaction between pathogens and BCAs, is not well known. Methods High‐throughput sequencing was used to identify the phyllosphere bacterial community of common vetch interacting with Colletotrichum spinaciae, two PGPRs (Bacillus subtilis and Bacillus licheniformis), and Trichoderma longibrachiatum. We evaluated anthracnose severity, phyllosphere bacteria diversity and composition, and the relationship between the activities of plant defense enzymes and hormonal molecules in plants treated with individual and combined inoculations of PGPRs, Trichoderma, and C. spinaciae. Results PGPR or Trichoderma alone reduced disease severity. Trichoderma reduced the salicylic acid content, PGPR increased the catalase activity in plants, and co‐inoculation of PGPR and Trichoderma decreased the salicylic acid content. Inoculation of PGPR and Trichoderma individually or in combination changed the disease‐associated phyllosphere bacteria, and this effect was related to plant defense enzymes and hormonal molecules. Conclusions We suggest that the plant defense response induced by PGPR and Trichoderma results in the enrichment of a fraction of favorable chloroplastic bacteria, which facilitates plant defense against diseases.

Agricultural practices can affect the diversity and community structure of soil fungi. This study investigates the impact of long-term agricultural practices on soil fungal diversity in the Loess Plateau of northwestern China. Different tillage practices have been implemented for 13 years, and their impact on soil fungi is assessed using high-throughput Illumina Sequencing. This study found a total of 2071 fungal Amplicon Sequence Variants (ASVs), and these were assigned to 25 different phyla, 372 families, and 496 genera. The fungal communities were dominated by Ascomycota (52.1%), followed by Zygomycota (14.3%) and Basidiomycota (9.0%). In general, the soil exhibited higher fungal community abundance, richness, and diversity in winter than in summer. Notably, no-tillage or stubble retention resulted in greater diversity than conventional tillage, with no-tillage combined with stubble retention resulting in the highest fungal richness, diversity, and network complexity in both summer and winter. These findings indicate that no-tillage with stubble retention is beneficial for biological soil components, which favors the establishment of abundant and diverse soil fungal communities in the Loess Plateau of China. The present study expands the knowledge of fungal communities in agro-ecosystems and the long-term ecosystem benefits of tillage practices.

Red clover (Trifolium pretense) is widely cultivated as an excellent forage and green manure crop. In 2021, a leaf spot disease was discovered in a red clover field in Min County, Gansu Province, China. Symptoms on T. pratense manifested as small white spots that gradually expanded into nearly oval or irregularly shaped gray-white lesions. The causal agent of this new disease was identified as Leptosphaeria weimeri (=Longiseptatispora meliloti) based on morphological identification, pathogenicity tests, and the phylogenetic identification of ITS, LSU, and SSU sequence. The optimal growth temperature was found to be 20 °C under different culture conditions, while the optimal spore-producing temperature was 25 °C. The pH for optimal growth and spore production was seven. The fungus grew and produced spores successfully on both PDA and PSA media. Additionally, the pathogen was efficiently inhibited using 450 g/L of prochloraz fungicide in vitro. To our knowledge, this is the first report of leaf spot disease on red clover caused by L. meliloti in China.