解脲沙雷氏菌鉴定及防控青枯病机理分析

Identification and mechanism analysis of Serratia ureilytica capable of controlling bacterial wilt

摘要:

【背景】番茄青枯病是番茄生产上常发的毁灭性病害，可造成番茄减产10%-100%，导致严重的经济损失。【目的】明确生防菌株BB183分类地位及对番茄青枯病的防治效果，为番茄青枯病的防控提供生防微生物资源。【方法】利用形态学特征、生理生化特性、基因组序列比较等方法，确定菌株BB183的分类地位；采用抑菌圈法测定菌株BB183对不同序列变种青枯菌菌株的抑菌活性；通过盆栽试验测定菌株BB183对番茄青枯病的防效及对番茄的促生能力效果；绿色荧光蛋白(green fluorescent protein, GFP)标记菌株测定BB183在番茄根、茎、叶及根际的定殖能力；采用三代PacBio和二代Illumina技术相结合测定菌株BB183基因组。【结果】菌株BB183被鉴定为解脲沙雷氏菌(Serratia ureilytica)；该菌株对分属6个序列变种的8株番茄青枯菌(Ralstonia solanacearum)菌株均有抑菌活性，抑菌圈直径1.20-1.69 cm；盆栽试验测定结果表明，菌株BB183对番茄青枯病的防效为51.67%，与20%噻森铜的防效相当，对番茄植株表现出显著的促生效果，并可稳定在番茄根际土壤中定殖。基因组分析结果表明，菌株BB183只包含1个环状的染色体，基因组大小为5 159 039 bp，G+C含量为59.35%，共编码4 664个基因；含有10个不同的次生代谢产物编码基因簇，其中包括3个抗生素类产物合成基因簇，4个铁载体相关产物合成基因簇，1个抗原相关产物合成基因簇和2种潜在的抑菌物质合成基因簇。【结论】筛选获得的生防菌株BB183为解脲沙雷氏菌，对番茄青枯菌具有良好的防治效果，对番茄也有较好的促生能力。

Abstract:

[Background] Tomato bacterial wilt is a devastating disease that occurs frequently in tomato production. It can reduce tomato yields by 10%-100% and lead to severe economic losses. [Objective] To clarify the taxonomic status of the biocontrol strain BB183 and its ability to control tomato bacterial wilt and to provide a biocontrol strain for the prevention and control of this disease. [Methods] Morphological, physiological, and biochemical characteristics and genome sequence information were used to determine the taxonomic status of strain BB183. The inhibitory activities of strain BB183 against different sequevars of Ralstonia solanacearum was determined via the inhibition zone method. The abilities of strain BB183 to control tomato bacterial wilt and promote tomato growth were determined via pot experiments. A green fluorescent protein (GFP) marker was used to measure the abilities of strain BB183 to colonize tomato roots, stems, leaves, and rhizosphere. Strain BB183 genome was sequenced via a combination of third-generation PacBio and second-generation Illumina technologies. [Results] Strain BB183 was identified as Serratia ureilytica. The strain demonstrated inhibitory activities against eight R. solanacearum strains belonging to six sequevars, with the inhibition zone diameter ranging from 1.20 cm to 1.69 cm. The results of pot experiments revealed that the control efficiency of strain BB183 on tomato bacterial wilt was 51.67%, which was comparable to that of 20% thiosen copper. Moreover, the strain significantly promoted the growth of tomato plants and stably colonized the rhizosphere of tomato plants. Strain BB183 contained only one circular chromosome, with a genome size of 5 159 039 bp and the G+C content of 59.35%, encoding a total of 4 664 genes. It carried 10 different gene clusters encoding secondary metabolites, including three for antibiotic synthesis, four for siderophore synthesis, one for antigen synthesis, and two for potential antimicrobial substances. [Conclusion] Strain BB183 obtained by screening was S. ureilytica, demonstrating strong effects of controlling tomato bacterial wilt and promoting tomato growth.