Rice blast, caused by the fungus Magnaporthe oryzae, can result in notable yield losses in rice production. The objective of this study was to investigate the potential of a rice endophytic isolate, Streptomyces albidoflavus OsiLf‐2, on the control of rice blast and the possible mechanisms involved. In vitro assays displayed a variety of antagonistic effects of OsiLf‐2 against different physiological races of M. oryzae, with peak mycelial growth inhibition ranging from 74.1% to 83.0%. In vivo tests of OsiLf‐2 showed 18.0% and 19.6% reduction in disease index in greenhouse and field conditions, respectively. The stable active metabolites in its cell‐free culture filtrate inhibited the mycelial growth, spore germination and appressorial formation of M. oryzae in a dose‐dependent manner. They also possessed strong antifungal capacities toward various phytopathogens in vitro. OsiLf‐2 secreted multiple antimicrobial compounds, cell wall degradation enzymes, siderophore, plant hormones, and 1‐aminocyclopropane‐1‐carboxylate deaminase, which might function in direct or indirect resistance to M. oryzae. In addition, a variety of defence responses were induced in OsiLf‐2‐treated rice, including hydrogen peroxide (H₂O₂) accumulation, callose deposition, defence‐related enzymes activation, and elevated expression of salicylic acid (SA) and jasmonic acid (JA) pathways genes, which might contribute in resisting pathogen attack. The significant biological control activity and host defence‐stimulation ability of OsiLf‐2 suggest that this endophytic actinobacterial strain could be a promising candidate in the management of rice blast disease.

中文翻译：

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抗稻瘟病的拮抗活性和内生链霉菌Albidoflavus OsiLf-2的宿主防御反应能力的激发

由稻瘟病菌引起的稻瘟病可导致稻米生产中的明显减产。这项研究的目的是研究水稻内生分离株，链霉菌Albidoflavus OsiLf-2对稻瘟病的控制及其可能的机制。体外试验显示OsiLf-2对米曲霉的不同生理小种有多种拮抗作用，其最高的菌丝体生长抑制作用范围为74.1％至83.0％。体内OsiLf-2的测试表明，在温室和田间条件下，疾病指数分别降低了18.0％和19.6％。无细胞培养滤液中稳定的活性代谢产物以剂量依赖的方式抑制了米曲霉的菌丝生长，孢子萌发和腹壁形成。他们还拥有对各种植物病原体的很好的抑菌能力体外。OsiLf-2分泌了多种抗菌化合物，细胞壁降解酶，铁载体，植物激素和1-氨基环丙烷-1-羧酸脱氨酶，它们可能直接或间接抵抗米曲霉。此外，在OsiLf-2处理的水稻中诱导了多种防御反应，包括过氧化氢（H ₂ O₂）积累，call质沉积，与防御相关的酶活化以及水杨酸（SA）和茉莉酸（JA）途径基因的表达升高，这可能有助于抵抗病原体的侵袭。OsiLf-2的重要生物防治活性和宿主防御刺激能力表明，该内生放线菌菌株可能是水稻稻瘟病管理中的有希望的候选者。