青稞根腐病防病促生细菌的筛选及其菌剂防效

Screening of bacteria with biocontrol effects against naked barley root rot accompany with plant growth-promoting properties and the biocontrol effects of the bacterial inoculant

摘要:

【背景】由燕麦镰孢(Fusarium avenaceum)和麦根腐平脐蠕孢(Bipolaris sorokiniana)等病原真菌引起的青稞(Hordeum vulgare L.var.nudum Hook.f.)根腐病普遍发生，对藏区农业生产和发展产生了极大威胁。【目的】从青稞健康植株根际土壤中筛选具优良防病促生能力的菌株，通过研究菌株间的互作效应以筛选优良菌剂配伍，制作防效优良的防病促生菌剂，以期为青稞根腐病的防治及青稞增产提供优质的菌剂资源。【方法】采用选择性培养基筛选促生菌株，采用平板对峙法筛选拮抗菌株；采用灌根法和叶面接种法测定菌株致病性；采用乙炔还原法测定固氮能力，钼蓝比色法测定溶磷能力，采用高效液相色谱法测定分泌吲哚乙酸能力；采用16S rRNA基因序列分析鉴定菌种；田间测定菌剂防效，并采用TOPSIS综合分析法进行综合评价。【结果】共分离出具固氮、溶磷能力菌株23株，并从中筛选得到6株拮抗能力良好的菌株，其中5株溶有机磷、3株溶无机磷、3株固氮菌，而且均分泌吲哚乙酸；测定其致病性发现对青稞、燕麦、油菜、豌豆等采样区常见作物均无致病性；经鉴定分别为枯草芽孢杆菌(Bacillus subtilis)2株、短小芽孢杆菌(Bacillus pumilus)1株、蜡样芽孢杆菌(Bacillus cereus)1株、荧光假单胞菌(Pseudomonas fluorescens)1株及不动杆菌(Acinetobacter sp.)1株；优化筛选得到7种优良组合(SC1-SC7)，选择其中4种最优组合(SC2、SC4、SC6和SC7)作为菌剂配方，制作液剂、粉剂和颗粒剂3种剂型菌剂，田间小区测定其防效，发现组合SC7(短小芽孢杆菌Xpq-3、蜡样芽孢杆菌Xpq-15和不动杆菌Xpq-21)液剂防病促生效果最佳。【结论】青稞根围土壤中存在有优良的防病促生菌株，利用其制作的菌剂对青稞根腐病有良好的防效。

关键词:青稞;根腐病;生防菌;植物根际促生菌

Abstract:

[Background] Naked barley root rot caused by pathogenic fungus such as Fusarium avenaceum and Bipolaris sorokiniana are widely occurred, which poses a great threat to agricultural production and development in Tibetan areas. However, there is still a few research on its biocontrol by bacterial inoculant in China. [Objective] To screen strains with excellent disease-controlling and plant growth-promoting properties from the healthy naked barley rhizosphere. Furthermore, we explored the interaction effects among the bacteria to screen the excellent inoculant formulas, and the bacterial inoculants were made accordingly. After all, our ambition is to provide superior microbial inoculants which catering for the biocontrol of naked barley root rot, promoting the crop yield as well. [Methods] Firstly, we used the selective media to screen growth-promoting strains and plate confrontation method to screen the disease-controlling strains. After determining the pathogenicity of the bacteria by root irrigation and foliar inoculation, the nitrogen fixation capacities, phosphorus dissolution capacities, and IAA secretion capacities of them were determined by acetylene reduction method, molybdenum blue colorimetric method and high performance liquid chromatography, respectively. Additionally, the bacteria were identified by 16S rRNA gene sequence analysis. Finally, the biocontrol effects of the inoculants were measured by field test and evaluated by TOPSIS comprehensive analysis method. [Results] A total of 23 strains with nitrogen-fixing and phosphorus-solubilizing abilities were isolated in the initial screening, and 6 bacteria among them with eminent antagonistic ability, including 5 organophosphorus solubilizing strains, 3 inorganic phosphorus solubilizing strains and 3 nitrogen-fixing strains, all of which secreted IAA. Besides, the pathogenicity of the bacteria showed no pathogenicity to common crops in the sampling area, such as naked barley, oat, rapeseed and pea. According to the identification result, the bacteria isolates include 2 Bacillus subtilis, 1 Bacillus pumilus, 1 Bacillus cereus, 1 Pseudomonas fluorescens and 1 Acinetobacter sp. As a result, we firstly optimized 7 combinations (SC1−SC7) and then selected the best 4 (SC2, SC4, SC6, SC7) as inoculant formulas. Moreover, they were all made into liquid, powder and accumulative bacterial inoculant severally. Eventually, the field plot biocontrol determination showed SC7 (Bacillus pumilus Xpq-3, Bacillus cereus Xpq-15 and Acinetobacter sp. Xpq-21) had the best biocontrol and plant growth-promoting effects. [Conclusion] It’s clear that there are amount of biocontrol and growth-promoting strains in the naked barley rhizosphere soil. In addition, the microbial inoculant made by them have excellent biocontrol effects.

Key words:naked barley;root rot;biocontrolbacterium;plant growth-promoting rhizobacteria (PGPR)