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[Objective] Kiwifruit bacterial canker (KBC), caused by Pseudomonassyringae pv. actinidiae (Psa), has become the primary bottleneck restricting the sustainable development of the kiwifruit industry in China, highlighting an urgent need for eco-friendly and residue-free biocontrol strategies. [Methods] The kiwifruit variety ‘Hongyang’ was used to systematically evaluate the biocontrol efficacy of Bacillus pumilus H-46 through leaf disc and shoot inoculation assays. The active components were fractionated into three groups (small-molecule metabolites, proteins, and polysaccharides) via sequential extraction, with the major bioactive fraction identified through antimicrobial activity and disease control assessments. An integrated approach combining histochemical staining, antioxidant enzyme activity assays, and RT-qPCR of defense-related genes was employed to elucidate the mechanism of induced systemic resistance (ISR). Furthermore, pathogen migration and colonization assays were conducted to evaluate the inhibitory effects of the active components against Psa. [Results] B. pumilus H-46 showed excellent control effect against KBC, with the disease control efficacy of 86.54% in leaf disc assays. Its main active components (small-molecule metabolites, fraction A) achieved the control efficacy of 88.16% against KBC through non-antimicrobial mechanisms. The mechanisms included triggering early H2O2 accumulation and callose deposition, significantly increasing superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities, and activating the expression of key genes (AcMYC2, AcAOC, AcERF2, and AcEIN3) in jasmonicacid (JA) and ethylene (ET) signaling pathways to activate ISR. Consequently, the disease resistance of kiwifruit was enhanced, resulting in a reduction of 37.8% in Psa migration distance in leaf veins and a decrease of 96.6% in colonization ability. [Conclusion] Our findings demonstrate that the small-molecule metabolites (fraction A) of B. pumilus H-46 activates JA/ET-mediated ISR via non-antimicrobial mechanisms, offering a sustainable solution for the control against KBC and establishing a prototype for next-generation plant immunity activators in crop protection.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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