一株具有防治水稻条斑病潜力的高地芽胞杆菌181-7

 水稻条斑病(Bacterial leaf streak, BLS)由稻黄单胞菌种下的致病变种条斑病菌(Xanthomonas oryzae pv. oryzicola, Xoc)侵染引起,已成为我国南方水稻种植区的一个重要病害。为了筛选防治BLS的生防细菌,本研究以Xoc的模式菌株RS105为靶标菌,采用平板稀释和抑菌圈法,从辣椒根际土壤中分离筛选到具有拮抗活性的菌株181-7。通过形态学、生理生化特征以及16S rRNA序列分析鉴定该菌株为高地芽胞杆菌,命名为Bacillus altitudinis 181-7。针对14种植物病原细菌和3种病原真菌的拮抗谱试验发现,181-7对Xoc和水稻白叶枯病菌(X. oryzae pv. oryzae, Xoo)表现特异性的拮抗作用,对禾谷镰刀菌也具有较明显的抑制作用。基因组信息显示,181-7携带一个环状的质粒,含有3 826个开放阅读框,含有涉及抗真菌、抗逆、诱导植物抗性和促进植物生长等特性的相关基因。AntiSMASH的分析显示,181-7含有地衣杆菌素(lichenysin)、丰原素(fengycin)、菌溶素(bacilysin)、细菌素(bacteriocin)以及噬铁素等抑菌活性代谢产物。温室的初步试验结果显示,在感病水稻品种‘原丰早'上, 181-7对Xoc在水稻叶片上引起的水渍症状具有明显的抑制作用。这表明, B. altitudinis 181-7具有防治水稻条斑病的潜力。这些研究为水稻条斑病的生物防治提供了新的微生物资源,也为后续生防机理的探究奠定了理论基础。

Bacillus altitudinis 181-7, a potential biocontrol agent against bacterial leaf streak of rice

Bacterial leaf streak (BLS) caused by Xanthomonas oryzae pv. oryzicola (Xoc), a devastating pathovar of Xanthomonas oryzae, is emerging as a serious disease in rice fields of Southern China. To obtain biocontrol bacteria with the potential to control BLS of rice, we screened bacteria with antibacterial activity from rhizosphere soil of hot pepper using petri dish dilution and inhibition zone assay against Xoc RS105. As a result, strain 181-7 was identified. Morphological, physiological and biochemical characteristics indicated that strain 181-7 could be classified as Bacillus altitudinis that was confirmed by molecular analysis based on 16S rRNA. We named the strain B. altitudinis 181-7. The inhibitory spectrum against fourteen plant pathogenic bacteria and three fungi showed that B. altitudinis 181-7 had specific antagonistic effects against Xoc and X. oryzae pv. oryzae (Xoo) and also effectively inhibited Fusarium graminearum. Genome sequencing revealed that B. altitudinis 181-7 carried a circular plasmid comprising 3 826 opening reading frames (ORF) as well as genes related to anti-fungal activity, stress resistance, inducing plant resistance and promoting plant growth. AntiSMASH analysis showed that B. altitudinis 181-7 contained genes associated with biosynthesis of antimicrobial compounds such as lichenysin, fengycin, bacilysin, bacteriocin and siderophore. Preliminary greenhouse assays showed that B. altitudinis 181-7 exhibited significantly inhibitory effects on water-soaked lesions caused by Xoc in the leaves of hypersusceptible rice cultivar ‘Yuanfengzao'. This indicated that B. altitudinis 181-7 had the potential as an effective biocontrol agent on diseases caused by Xoc. Our study has provided a new microbial resource for the biocontrol of BLS, and also laid a theoretical foundation for the research on biological disease control mechanism.