象耳豆根结线虫2龄幼虫生防细菌的筛选及其促生特性评价

Screening of Biocontrol Bacteria Against Second-stage Juveniles of Meloidogyne enterolobii and Evaluation of the Growth-promoting Characteristics

象耳豆根结线虫(Meloidogyne enterolobii)引起的作物根结线虫病是一种严重危害热区农作物生产的土传病害,每年造成的农业损失难以估量。对于根结线虫的防治,传统的物理、化学的防治手段存在一些弊端,而生物防治对环境友好、人畜安全,因此逐渐成为研究热点。本研究采用浸渍法筛选出对象耳豆根结线虫2龄幼虫具有抑杀活性的菌株,对筛选出的高活性菌株的发酵条件以及处理时间进行优化,利用16S rRNA序列及生理生化方法对菌株进行鉴定,并分析其促生特性。结果表明:有3株菌的发酵上清液杀线活性高于65%,分别为BWLY1PSB-1、BWLY2X-4、BWLY3X-11。通过形态特征、生理生化特征以及分子生物学鉴定,将BWLY1PSB-1鉴定为巴氏葡萄球菌(Staphylococcus pateuri),BWLY2X-4鉴定为甲基营养芽孢杆菌(Bacillus methylotrophicus),BWLY3X-11鉴定为芽孢杆菌属(Bacillus sp.)细菌;利用各菌株的发酵上清液处理线虫24h后,其杀线活性即可达到最大,优适发酵培养基均为LB培养基,且培养5d时上清液对线虫达到较好的致死率。BWLY1PSB-1具有产生铁载体和吲哚乙酸的能力,BWLY2X-4和BWLY3X-11具有产生蛋白酶、纤维素酶、铁载体和IAA的能力。本研究初步筛选出既能高效防控植物根结线虫又具有植物促生特性的优良菌株,丰富了植物根结线虫生物防治的微生物资源。

Meloidogyne enterolobii is a soil-borne disease that seriously harms crop production in tropical areas,and the agricultural losses caused by it are incalculable every year.For the control of root-knot nematodes,the traditional physical and chemical control methods have some disadvantages,while biological control is environmentally friendly and safe for people and livestock,so it has gradually become a research hotspot.This study used the impregnation method to screen strains with killing activity against the second instar larvae of M.enterolobii.The fermentation conditions and treatment time of the screened highly active strains were optimized.The strains were identified using 16S rRNA sequencing as well as physiological and biochemical methods,and growth promoting characteristics were analyzed.The research results indicated that the nematicidal activity of the fermentation supernatant of BWLY1PSB-1,BWLY2X-4 and BWLY3X-11 were more than 65%.Through morphological,physiological and biochemical characteristics,and molecular biology identification,BWLY1PSB-1,BWLY2X-4 and BWLY3X-11 were identified as Staphylococcus pateuri,Bacillus methylotrophicus and Bacillus sp.,respectively;The nematicidal activity of the fermentation supernatant of each strain could reach the maximum after 24 h treatment of nematodes,and the optimal fermentation medium was LB medium,and the nematicidal activity of the supernatant reached relatively high when cultured for five days.The research results on the growth promoting characteristics of thee strains indicated that BWLY1PSB-1 had the ability to produce iron carriers and IAA,while BWLY2X-4 and BWLY3X-11 had the ability to produce proteases,cellulases,iron carriers,and IAA.The preliminary screening of excellent strains that can effectively control plant root-knot nematodes and have rowth promoting characteristics would enrich the microbial resources for the biological control of plant root-knot nematodes.