橡胶/木薯间作体系化感作用对胶园土壤微生物调节研究

Rubber tree and cassava are important economic crops for tropic and subtropic areas in China. Intercropping cassava in young rubber plantation is one of effective ways to ensure the healthy development of the two industries. But there is a controversy for the rationality of this intercropping system in academic circles. The argument mainly concentrated whether intercropping cassava will result in soil fertility decline and cause the diseases occur. Our previous studies showed that the rubber yield was related to the soil microbial community presented, and that root exudates and plant residues of cassava effect the number of soil microbe and the occurrence of diseases. So we hypothesize that key of the problem is the allelopathy in the intercropping system on the soil microbe. Based on the points of divergence, Real-Time PCR technique will be used to detect the number of microbe, and DGGE method will be used to analyze the effect of root exudates and plant residues to assay the microbial diversities, combined with influence of root exudates and plant residues on the growth and spore germination of pathogen in vitro dual-culture on plates technology in this study. The project will elucidate the mechanism on how intercropping system increased the crop production and cultivation efficiency, and it will provide theoretical basis for intercropping cultivation pattern promotion and enhance the production efficiency of tropic crops.

橡胶和木薯是我国热带亚热带地区重要的经济作物，幼龄胶园间作木薯是保证两大热作产业健康发展的有效途径。然而，学术界对该间作模式的合理性存在着争议，影响着此模式的推广和应用。分歧点集中在间作木薯后橡胶树病害发生是否增加，橡胶园地力是否减退引起胶乳产量降低两个方面。前期研究表明：木薯根系分泌物和器官浸提液影响土壤微生物的数量和作物病害的发生；胶园土壤微生态环境与胶乳产量存在着正相关。故我们推测：间作体系的化感作用对胶园土壤微生物变化是分歧点的关键。本研究拟从分歧点入手，采用Real-Time PCR技术测定微生物数量、DGGE技术测定土壤微生物多样性，结合平板对峙技术分析根系分泌物和残体浸提液对病原菌菌丝生长与孢子萌发的影响，阐明间作体系化感作用对胶园土壤微生物的影响。研究结果可望找出制约该模式增产增效的具体原因，回答现有的学术分歧，最终为此间作模式的推广及其高产高效栽培等提供理论依据。

幼龄胶园间作木薯这一模式的合理性一直存在着争议。本课题首先提取木薯根系分泌物、器官浸提液和腐解物浸提液等木薯化感物质，然后采用平板试验分析上述木薯化感物质对橡胶树棒孢霉落叶病与橡胶树白根病病菌的化感效果，盆栽试验分析上述木薯化感物质对土壤微生态、橡胶树白根病的发病率及其生长的影响。同时，通过大田试验分析施肥和不施肥情况下间作与单作胶园、不同间作年限之间胶园土壤的微生态差异。结果显示：⑴根系分泌物对橡胶树白根病病菌的化感效果与对照均无显著差异,而对橡胶树棒孢落叶病病菌呈现化感促进效果，且浓度越大化感促进效果越明显。腐解物浸提液对橡胶树棒孢霉落叶病和白根病病菌表现出一定程度的化感抑制效果；茎浸提液对橡胶树棒孢落叶病病菌、叶浸提液对橡胶树白根病病菌表现出一定程度的化感促进效果。⑵不管浇灌哪一浓度的木薯化感物质对均提高了盆栽的橡胶树土壤肥力，且浓度越大，对提高土壤肥力的效果越大。⑶若胶园不施肥，相对单作胶园，间作木薯可显著降低碱解N、速效磷、速效钾和有机质含量，降低胶园土壤真菌的群落多样性，增加病原型真菌的丰度，且随着间作年限的延长，肥力下降越明显，但是，若间作胶园同步增加施肥量，则相对单作胶园，可提高胶园土壤肥力。综合上述结果，本研究可回答现有的学术分歧，找出了制约幼龄胶园间作木薯的增产增效的具体原因，为该间作模式的推广与高产高效栽培提供了一定的理论依据。项目资助发表核心论文3篇，待发表1篇，培养硕士生2名，均已经取得硕士学位。项目投入直接经费39万元，支出35.2989万元，各项支出基本与预算相符。剩余经费计划用于本项目研究后续支出。