基于土壤线虫群落特征的连作番茄根结线虫病发生机制

Root-knot nematodes, one of the most important agricultural pests of vegetables, are responsible for large yield losses in several horticultural crops. The root knot nematode population is one of population in soil nematode communities. However, little is known about the relationship between root knot nematodes and other soil nematodes, the changes in the diversity of the soil nematode population and natural microbial enemies during cotinuous cropping. Likewise, coupling effects of root knot nematodes and microbial enemies is not well understood. Therefore, this project will study the outbreak mechanism of root-knot nematodes based on the diversity of soil nematodes and their natural microbial enemies using molecular microbial ecology and traditonal taxonomy methods. In addition, we will further study the reason for the large root-knot nematode populations in long-term continously cropped soil based on the community dynamics of the soil nematodes and their natural microbial enemies using the results of a previous study we conducted, which showed the relationship between root-knot nematodes and free-living nematodes in the soil to different durations of continuous cropping. The experiment will be carried out in field scale and pots experiment to study the soil of continously cropped tomato. The objectives of the current study are: (1) to determine the dynamics of the soil nematode community diversity with increasing durations of continous cropping using terminal restriction fragment length polymorphism (T-RFLP) and traditional taxonomy techniques; (2) to determine the dynamics of soil microbial community diversity with increasing duration of continous cropping using T-RFLP; (3) to study and analyze relationship between the disease index of root-knot nematode and nematode population; and (4) to assess the relationship between root-knot nematodes, the soil nematode community, and the natural microbial enemy community in the soil. The research results will provide important theoretical information on molecular markers of root-knot nematodes that can serve as early warning systems of disease outbreaks.

根结线虫病是蔬菜生产中的重要病害之一，连作是该病害加重的主要原因。根结线虫群体作为土壤线虫群落的组成，在连作过程与土壤中其它线虫群体之间关系如何？土壤中线虫微生物天敌群体如何演替？它们之间的联动效应等均不清楚。本研究利用微生物分子生态学原理结合传统研究方法，基于土壤线虫群落结构和微生物天敌的多样性，研究连作番茄根结线虫病灾变机理。前期研究明确了连作土壤自由生活线虫与根结线虫群体之间关系，在此基础上有必要利用土壤线虫群落结构、线虫微生物天敌与根结线虫群体关系深入研究连作土壤根结线虫群体上升的机制。主要研究内容包括：1、应用末端限制性酶切片段长度多态性（T-RFLP）技术和传统分类学对连作土壤线虫多样性分析；2、连作土壤线虫和微生物群落的演替分析；3、根结线虫群体数量与病情关系研究；4、土壤线虫、微生物天敌群落及与根结线虫群体关系研究，为进一步获得根结线虫病早期预警的分子标记研究提供理论基础。

根结线虫是蔬菜上一种主要的病原，在我国南方发生普遍，本研究以亚热带气候下的冬种番茄为研究对象，研究番茄生长期间根围根结线虫群体的动态变化。结果表明：2014–2016番茄的整个生育期，在根围土壤中均检测到根结线虫二龄幼虫（J2）。根据盖斯和法拉利生长期间根结线虫J2的数量推断出根结线虫共发生3代。第一代发生在番茄开花早期，第二和第三代发生在结果期和收获期。不同番茄品种根系的根结数量有显著差异（P＜0.05）。嫁接苗根围土壤中J2的数量显著高于实生苗根围的J2数量，嫁接苗折合每公顷为291.32 kg，和1649.45 kg，是实生苗产量的3.6倍，研究结果明确根结线虫病的发病规律。通过阿维菌素和阿维菌素B2分别与噻唑膦进行复配，利用浸泡法检测，寻找对番茄根结线虫J2毒杀效果好的配比农度，并用盆栽试验进行验证，明确复配制剂防治番茄根结线虫的最佳配比，为复配药剂防治番茄根结线虫病的效果、合理性及最终进入田间药效试验阶段提供理论依据。评价阿维菌素、阿维菌素B2与噻唑膦复配对根结线虫的生物活性并筛选出最佳增效配比。.高通量测序结果显示，番茄-水稻轮作（SD1）的试验小区土壤中的微生物群落与番茄连作（FQ1）和空闲试验小区（CK1）的微生物群落差异显著。FQ1土壤中被检测到的真菌、细菌和线虫OUTs数分别为149、524和19，SD1中为185、572、15，CK1中为177、588、22；SD1中，真菌菌群，细菌菌群和线虫类群的丰度明显高于FQ1；Ascomycota等7个真菌菌群、Mizugakiibacter等4个细菌菌群和Mesocriconema等6个线虫类群的丰度明与FQ1相比，明显减少。说明轮作可减少植物寄生线虫类群丰富度。SD1中根结线虫2龄幼虫数量为3.1 头/100 g 干土，少于FQ1（10.0头/100 g 干土）和CK1（4.4头/100 g 干土），说明番茄-水稻轮作模式能够降低土壤中根结线虫2龄幼虫数量。