Bacterial and fungal diseases cause significant losses in horticultural crops, and biocontrol using beneficial microorganisms offers a sustainable alternative to chemical pesticides. In this study, a novel Pseudomonas strain D3 was isolated from Actinidiae rhizosphere. D3 exhibited strong antibacterial activity in LB medium but showed no activity against fungi or oomycetes. However, when cultured in KIDO medium, it demonstrated potent antifungal activity. Phylogenetic analysis based on 16S rRNA gene showed that D3 was most closely related to Pseudomonas mosselii CIP_105259T, while whole-genome sequencing revealed ANI values below 95% with eight known P. mosselii strains. Digital DNA-DNA hybridization (dDDH) further confirmed its genomic distinctiveness, with the highest dDDH value (58.2%) against the type strain P. mosselii DSM 17497T, well below the 70% species delineation threshold, supporting D3 as a novel Pseudomonas species. Functional validation via targeted gene knockout revealed a dichotomy in the antagonistic mechanisms of D3. Knockout of individual biosynthetic gene clusters (BGCs) only partially reduced antibacterial activity against Pseudomonas syringae pv. actinidiae, indicating that multiple BGCs contribute to this activity in a partially redundant manner. In contrast, disruption of a specific lipopeptide synthase cluster completely abolished antifungal activity against Valsa mali. LC-MS/MS analysis confirmed that this lipopeptide was produced exclusively in KIDO medium, consistent with the observed medium-dependent antifungal activity. Detached leaf and twig assays showed that D3 provides strong preventive biocontrol against both pathogens. Collectively, strain D3 employs a dual biocontrol mechanism, combining antibacterial activity mediated by multiple BGCs with lipopeptide-dependent antifungal activity, positioning it as a promising agent for sustainable disease management in horticultural crops.
Ming-Ming Yang, Guang-Zhe Li, Yun-Cong Wang et al.· Pesticide Biochemistry and P...· 0 citations
Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a major constraint to wheat production in China. Although the disease occurs in Tibet every year under the favorable weather conditions, the virulence diversity and population structure of the Pst population in this region remain poorly understood. In this study, 312 Pst isolates collected in 2025 from five major wheat-growing regions of Tibet (Qamdo, Nyingchi, Lhasa, Shannan, and Shigatse) were characterized using virulence phenotyping and the Pst 5K genotyping-by-target-sequencing (GBTS) platform. Virulence testing on 19 Chinese differentials identified 139 races, including 88 previously reported and 51 novel races, with Su11-3, HY-009-1, and CYR34 being the predominant races. Testing the isolates with 18 Yr single-gene differentials identified 190 virulence phenotypes. None of the isolates were virulent to Yr5 or Yr15, whereas virulence frequencies to the remaining Yr genes ranged from 2.2% to 89.7%. Population genetic analyses using the GBTS data revealed clear regional differentiations. The Nyingchi population formed a distinct cluster with relatively low genomic diversity despite maintaining considerable virulence diversity, whereas the Lhasa and Shannan populations showed extensive admixture.The Qamdo and Shigatse populations consisted of unique genetic components and exhibited relatively high levels of virulence and genetic diversities. Combined virulence and genomic analyses indicated region-specific epidemiological characteristics and suggested that Qamdo may represent an important center of Pst diversification, whereas Lhasa and Shannan may facilitate pathogen dispersal and gene exchange. This study provides the first comprehensive assessment of Pst populations across Tibet and offers valuable information for disease surveillance, resistance breeding, and integrated management of wheat stripe rust in Tibet and neighboring wheat-growing regions.
Li Geng, Ying Li, Hexin Chen et al.· Plant Disease· 0 citations
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