Cotton Verticillium wilt is a disease that significantly impacts the cotton industry, severely affecting cotton quality and the economic well-being of farmers. Bacillus atrophaeus YL84 is a biocontrol bacterium with broad-spectrum antagonistic and growth-promoting characteristics, previously isolated by our laboratory. This study aimed to elucidate the antagonistic effects of sterilized fermentation filtrate from Bacillus atrophaeus YL84 on cotton Verticillium wilt pathogen Verticillium dahliae and its growth-promoting effects on cotton. The experiments were conducted in vitro and in vivo to assess these effects comprehensively. Using the dual culture method, it was found that Bacillus atrophaeus YL84 exhibited a high inhibition rate on mycelial growth of V. dahliae, with an inhibition rate of 84.11%. The undiluted YL84 sterilized fermentation filtrate and its 10% volume fraction dilution (fermentation filtrate diluted to 10%) exhibited inhibition rates of 80.25% and 72.16% for conidial germination and mycelial growth of V. dahliae, respectively. Scanning electron microscopy showed increased branching, swelling, and shortened internodes in the antagonized mycelia. Conductivity measurements revealed a significant enhancement caused by the YL84 filtrate, with conductivity increasing by 8.94 times compared to the control at a 250 μg/mL concentration. Similarly, protein leakage peaked at 9.47 times the control level at 250 μg/mL, demonstrating the filtrate’s potent impact on mycelial cell membrane permeability. The enzymatic activities of polygalacturonase (PG), cellulase (CL), and β-glucosidase (β-GC) were significantly reduced following treatment with YL84 sterilized fermentation filtrate, with reductions from control levels of 15.78, 10.11, and 5.01 U/mL to treatment levels of 11.81, 6.96, and 1.44 U/mL, respectively. Indoor pot experiments demonstrated that different concentrations of YL84 sterilized fermentation filtrate significantly suppressed the occurrence of cotton Verticillium wilt while promoting plant growth. Compared to the control group, application of 250 μg/mL YL84 sterilized fermentation filtrate resulted in a control efficacy of 66.69% for cotton Verticillium wilt, with increases in plant height, root length, fresh weight, and dry weight of 9.36–33.85%, 17.33–29.49%, 16.79–28.24%, and 25–58.33%, respectively. These findings underscore the potential of the YL84 filtrate as both a biocontrol agent and a promoter of cotton plant growth in agricultural settings. These results indicate that Bacillus atrophaeus YL84 sterilized fermentation filtrate possesses both disease-suppressing and growth-promoting activities, making it a promising candidate for development and use as a biocontrol agent and plant growth promoter.

To evaluate the biocontrol potential of the cell-free fermentation filtrate (CFFF) of Bacillus atrophaeus strain YL84 against Fusarium oxysporum f. sp. vasinfectum (FOV), this study systematically investigated the effects of the CFFF at various dilution ratios on FOV mycelial growth, conidial germination, cellular nucleic acid leakage, and malondialdehyde (MDA) content. Furthermore, the environmental stability of its antifungal activity was assessed. In addition, a dual-culture assay was conducted to evaluate the antagonistic activity of strain YL84 against FOV. The results of the dual-culture assay showed that strain YL84 significantly inhibited the growth of FOV, with an inhibition rate of 81.06%. Subsequently, the YL84 CFFF exerted significant inhibitory effects on FOV mycelial growth and conidial germination across different concentrations, achieving maximum inhibition rates of 75.68% and 77.56%, respectively. Notably, the treated mycelia exhibited a significant increase in cellular nucleic acid leakage and elevated levels of MDA, a product of lipid peroxidation, suggesting that the CFFF may disrupt the integrity of the pathogen’s cell membrane. Stability assays revealed that the CFFF possessed substantial tolerance to high temperatures, ultraviolet irradiation, and hypersaline environments, although it remained sensitive to strongly alkaline conditions. Greenhouse pot experiments further confirmed the efficacy of YL84 CFFF in controlling cotton Fusarium wilt, with a maximum control efficacy of 69.21%. Moreover, the treatment induced the upregulation of defense-related enzyme activities in the plants, suggesting that the CFFF may function through both direct antifungal action and the elicitation of host-induced resistance. Component identification via Ultra-Performance Liquid Chromatography–Ion Mobility–Quadrupole Time-of-Flight Mass Spectrometry (UPLC-IMS-Q-TOF-MS) suggested that the filtrate is rich in structurally diverse compounds that were putatively identified as potential antimicrobial substances, predominantly classified as terpenoids and their derivatives. In conclusion, this study provides a systematic evaluation and supporting evidence for the further development of B. atrophaeus YL84 as a biocontrol agent.

Fragrant pear canker, caused by Cytospora pyri, is a major branch disease that reduces the productivity and longevity of Korla fragrant pear orchards in Xinjiang, China. During infection and lesion expansion in woody tissues, C. pyri must breach the host cell wall barrier, in which pectin degradation plays a central role by weakening intercellular adhesion and disrupting tissue integrity. Members of glycoside hydrolase family 28 (GH28), represented mainly by polygalacturonases and other pectin-degrading enzymes, are closely involved in fungal invasion and colonization. However, the composition and virulence-related functions of this gene family encoding for these enzymes in C. pyri remain unclear. In this study, GH28 genes were systematically identified and comparatively analyzed in C. pyri and closely related Cytospora species. Infection-stage expression profiling and functional validation were then performed to assess their roles in pathogenicity. A total of 73 GH28 genes were identified across five Cytospora species, including 15 in C. pyri. Most C. pyri GH28 proteins were predicted to be acidic, hydrophilic, extracellularly secreted proteins carrying conserved motifs. Phylogenetic analysis showed that C. pyri GH28 members were closely related to homologs from C. mali. Genomic distribution analysis revealed that these genes were dispersed across multiple scaffolds, with no obvious tandem duplication events. RT-qPCR analysis showed that all seven candidate GH28 genes were induced during infection of fragrant pear branches, with VP1G_08835 and VP1G_03209 exhibiting strong expression responses at 6 dpi. Functional validation further showed that deletion of VP1G_08835 impaired vegetative growth and reduced lesion length on detached pear branches by 26.62% compared with the wild type, whereas complementation restored these phenotypes. These findings demonstrate that GH28 genes participate in C. pyri infection and identify VP1G_08835 as an important GH28 member required for normal growth and contributing to virulence.

Aphis gossypii (Glover) (Hemiptera: Aphididae) is a significant pest in cotton fields, and the use of both chemical insecticides and natural enemies is a crucial strategy for its management. Hippodamia variegata (Goeze) (Coleoptera: Coccinellidae), a predominant predatory natural enemy in cotton fields, plays a vital role in controlling A. gossypii populations. In this study, we investigated the toxicity of four insecticides to both A. gossypii and H. variegata larvae, assessed their field efficacy against A. gossypii, and evaluated their effects on the predatory function of H. variegata larvae. The results revealed that afidopyropen and spirotetramat exhibited relatively high toxicity against A. gossypii, with LC₅₀ values of 13.18 mg/L and 22.17 mg/L, respectively. Flonicamid demonstrated the least toxicity to H. variegata larvae, with an LC₅₀ of 512.66 mg/L. The selectivity toxicity ratios for afidopyropen and flonicamid were 5.05 and 4.73, respectively, indicating strong, favourable selectivity towards H. variegata. The maximum field control efficacy against A. gossypii was 96.76% for afidopyropen and 96.92% for flonicamid. The reduction rates of H. variegata larvae in the afidopyropen treatment plots were relatively low. Among the four treatments, the theoretical predation of third-instar H. variegata larvae against A. gossypii was highest with flonicamid, reaching 215.67. Overall, the four insecticides differed substantially in their combined effects on aphid suppression and predator performance. In particular, afidopyropen and flonicamid provided excellent control of A. gossypii while showing comparatively lower toxicity to H. variegata and causing less impairment of its predatory capacity, indicating a more favourable biological trade-off between pest control and natural enemy conservation. However, laboratory toxicity and functional response assays may not fully capture predator–prey dynamics under complex field conditions; therefore, afidopyropen and flonicamid may be considered suitable candidate insecticides for inclusion in integrated pest management (IPM) programs in cotton systems.

To identify the primary pathogen responsible for brown rot in mature Korla fragrant pears and to screen for effective biocontrol bacterial strains, a research team collected 30 samples of brown rot-infected fruits and 84 samples from healthy trees (including branches, leaves, and fruits) from three Korla pear cultivation areas in Korla, Aksu, and Kashgar between September and October 2024. Investigation into the severity of the disease revealed the local field incidence rate of brown rot ranged from 17% to 31%. From the 30 disease samples, 23 morphologically identical fungal strains were isolated, with 13 strains isolated from Korla City (56.5%), 6 from Aksu City (26.1%), and 4 from Tumushuk (17.4%), all detected in infected fruits. Pathogenicity tests were conducted using both inoculation by wounding with mycelium and spray inoculation experiments to study the pathogens’ effect on brown rot in Korla fragrant pears. From the 84 samples of healthy trees, 55 bacterial strains were isolated, and the antagonistic bacteria’s inhibitory effect on the isolated pathogens was determined using the dual-culture method. The pathogen was identified by morphological characteristics and phylogenetic analysis based on multi-locus sequencing (ITS-TUB2-Lcc2). Antagonistic bacterial strains were identified through morphological observation and 16S rDNA sequencing. The results demonstrated that the pathogen isolated from the diseased Korla fragrant pear tissues was identified as Monilinia yunnanensis. Among the biocontrol antagonistic bacteria isolated from the branches, bark, and leaves of healthy Korla fragrant pear trees, Bacillus siamensis exhibited significant inhibitory effects against the pathogen, with an in vitro inhibition rate of (88.18 ± 3.43)%.

Bacillus atrophaeus has considerable potential for development as a microbial pesticide. Optimization of fermentation conditions and the wettable powder (WP) formulation is critical for its industrialization and application in sustainable agriculture. In this study, the fermentation of B. atrophaeus YL84 was optimized using single-factor experiments and response surface methodology. Based on these results, a WP formulation was developed and further optimized. The optimal carbon, nitrogen, and inorganic salt sources were sucrose (13.9 g·L⁻¹), tryptone (11.8 g·L⁻¹), and MgSO₄ (5.9 g·L⁻¹), respectively; optimal fermentation conditions were pH 7.0, 32 °C, and 210 r·min⁻¹. After optimization, the inhibition rate and OD₆₀₀ reached 83.71% and 1.758, respectively. The optimized formulation comprised attapulgite-based powder (79%, as carrier), sodium alkyl naphthalene sulfonate (5.4%) as a wetting agent, PEG-6000 (12.6%), CaCO₃ (2%), and vitamin C (1%). The resulting WP exhibited a spore viability of 2.63 × 10⁹ CFU·g⁻¹, and its 50-fold dilution demonstrated antagonistic activity in vitro against Cytospora pyri (Korla pear valsa canker agent) and biocontrol efficacy in vivo on detached-branch assays. These findings demonstrate that the YL84 WP is a promising candidate for the biological control of Korla pear valsa canker.