西瓜枯萎病生防细菌YZU-S8的筛选及其防病促生作用的研究

Screening of Biocontrol Bacterium YZU-S8 against Fusarium oxysporum f.sp.niveum and Its Effect on Disease Control and Growth Promotion

【目的】分离和筛选对西瓜枯萎病菌有拮抗作用的细菌,为其生物防治提供更多更优质的菌源。【方法】从荆州市油菜田中采集长势良好的油菜植株,收集其根际土,采用稀释涂布法分离内生细菌及根际细菌。通过平板对峙筛选对西瓜枯萎病菌(Fusarium oxysporum f.sp.niveum)具有较强拮抗作用的菌株,经16S rDNA序列比对分析结合系统发育树对其进行鉴定,测定其抑菌谱,并通过温室盆栽实验测定其对西瓜植株的促生作用和在不同接种时间下对西瓜枯萎病的防效。【结果】从油菜植株及其根际土样品中共分离得到127株细菌,其中有17株细菌对西瓜枯萎病菌表现出了抑制作用,抑制作用最强的是一株内生细菌,命名为YZU-S8。该菌株具有广谱的抑菌活性,其无菌滤液在不同浓度下对9种病原真菌均具有一定的抑制作用,浓度为20%时对供试病原真菌的抑制率为40.35%~98.95%。提前3 d接种菌株YZU-S8时,该菌株能明显减轻西瓜植株的发病程度,对西瓜枯萎病的防效为73.8%。经YZU-S8灌根处理后西瓜植株的长势更加旺盛,其主蔓长和根长分别增加了8.01 cm和8.34 cm,地上鲜质量增加了6.88 g。16S rDNA序列分析显示YZU-S8与贝莱斯芽孢杆菌(Bacillus velezensis)的相似度达到100%,结合系统发育进化树将其初步鉴定为贝莱斯芽孢杆菌。【结论】菌株YZU-S8对西瓜植株具有显著的促生作用,对西瓜枯萎病具有良好的生防潜力和开发前景。

[Objective]To isolate and screen antagonistic bacteria against Fusarium oxysporum f.sp.nive⁃um,and provide more and better bacterial sources for controlling watermelon Fusarium wilt.[Method]Rapeseed plants with good growth were collected from rapeseed fields in Jingzhou City,and their rhizosphere soil was collected.Endophytic bacteria and rhizosphere bacteria were separated by a serial dilution method.The antagonistic strains against Fusarium oxysporum f.sp.niveum were screened by dual culture,and their inhibition spectrum was determined.The bacteria were identified by 16S rDNA sequence alignment analysis combined with phylogenetic tree.The control effect of the bacteria on watermelon Fusarium wilt and the growth promoting effect on watermelon plants were determined by pot experiment.[Result]A total of 127 bacteria were isolated from rapeseed plants and their rhizosphere soil samples,of which 17 bacteria showed inhibitory effects on watermelon Fusarium wilt pathogen,and the one with the strongest inhibitory effect was an endophytic bacterium named YZU-S8.The strain had broad-spectrum bacteriostatic activity,and its culture filtrates showed inhibitory effect on nine pathogenic fungi at different concentrations.The inhibitory rates of the culture filtrates against the tested pathogenic fungi were 40.35%-98.95%at a concentration of 20%.When inoculated with strain YZUS83 d earlier,the strain could significantly reduce the incidence in watermelon plants,and the control effect on watermelon wilt was 73.8%.After root irrigation with YZU-S8 suspension,the growth of watermelon plants was more vigorous.The main stem length and root length of watermelon plants were increased by 8.01 cm and 8.34 cm respectively,and the fresh weight above ground was increased by 6.88 g.16S rDNA sequence analysis showed that the similarity between YZU-S8 and Bacillus velezensis reached 100%,which was preliminarily identified as B.velezensis in combination with phylogenetic evolutionary tree.[Conclusion]Strain YZU-S8 has significant growth-promoting effect on watermelon plants,and has good biocontrol potential and development prospect to watermelon Fusarium wilt.