Mechanism of biological suppression of replant failure and the utilization of antagonistic microorganisms against Phytophthora blight of red pepper.

为明确连作土壤中微生物对辣椒疫病的抑制作用，建立合理利用拮抗微生物进行生物防治的方法，研究了辣椒疫病菌（Phytophthora capsici Leonian）对连作土壤中微生物的抑制作用。结果表明：1.比较抑制和促进辣椒疫病发生的土壤，抑制力的大小与土壤微生物学性状的关系比土壤理化性质的关系更密切.施用有机物料可降低辣椒疫霉侵染的严重程度，其中稻草在秋季温和季节的抑制作用最强.从抑制性土壤中分离的拮抗微生物中，绿色木霉和尼日尔对辣椒疫霉侵染的抑制效果最好.对疫病菌的抑制力与土壤的抑菌作用密切相关，使病原菌种群数量显著下降.土壤的抑菌作用与培养物和土壤中β-葡聚糖酶和纤维素酶的活性也有很好的相关性。几丁质酶活性与抑菌作用无关.辣椒疫霉菌丝细胞壁主要由β-葡聚糖和纤维素组成，并含有少量几丁质，表明辣椒疫霉菌丝对疫病菌的杀菌作用是由两种酶水解细胞壁组分而引起的。

Replant failure has been a serious limitation for a continuous cropping of red pepper because it is susceptible of phytophthora blight Phytophthora capsici Leonian.This study has been performed to clarify the microbiological suppression of the cultivated soils against the injury by continuous cropping of red pepper and establish the rational use of antagonistic microorganisms for the biological control. The results presented here show that:1. Comparing the soils suppressive and conducive to phytophthora blight of red pepper, the magnitude of suppressive force is more closely related to soil microbiological characters than physical and chemical properties of soils.2. Suppression of the infection of red pepper by P. capsici with application of some organic matters can be rendered decreased in the severity, among of which rice straw amendment was most suppressive during the mild temperature season at autumn.3. Among antagonistic microorganisms isolated from suppressive soils, Trichoderma viride and Aspergillus niger led the most effectively to lessen infection of red pepper by P. capsici.4. Suppressive force against Phytophthora blight was closely related to fungilytic action of soils so that the population of the pathogen remarkably decreased.5. The fungilytic action of soils also well correlated with the activities of both beta-glucanase and cellulase in inculants and soils. chitinase activities however,had no connection with fungilytic action.6. The hyphal cell wall of P.capsici is primarily made up of beta-glucan and cellulose and contained a few amount of chitin, which suggested that mechanism of fungilytic action against phytopthora blight was attributed to two enzyme activities, hydrolysing the cell wall components.