Study of control systems for soil-borne diseases by indigenous microbial diversity

在植物病害防治中，利用天然、安全的微生物作为生物防治系统是非常有希望的。然而，这种疾病控制系统经常被声称其效果不一致。因此，我们进行了一系列实验，旨在利用本土微生物多样性开发出对土传疾病安全和一致有效的疾病控制系统。本研究项目取得的具体成果如下。(1)土传病害与土壤微生物多样性的关系分析：在田间条件下，将野燕麦作为绿肥应用于番茄黄萎病的防治，在田间条件下，利用PCR-DGGE、FAME和CLPP对土壤微生物群落的变化进行了监测。另一方面，小麦-麸皮配水对番茄枯萎病和青枯病的抑制作用，即‘土壤减量土壤消毒’…。从病原菌密度和兼性厌氧菌两个方面进行了研究。后者通过克隆DGGE条带进一步鉴定细菌。此外，还用高效液相色谱法测定了活动期间产生的有机酸。(2)土传病害与土壤共生丛枝菌根(AM)多样性的关系分析：AM既能保护植物免受各种环境胁迫的伤害，又能提供磷等无机养分。因此，为了阐明土壤AM多样性与抑制土传病害之间的关系，利用脂肪酸甲酯(FAME)测定了定植植物根部的AM多样性。具体地说，来自AM的FAME组分，例如16：1的ω5，在健康和患病(感染黄萎病)的茄子根之间进行了比较。结果表明，茄子黄萎病病根和健根的菌丝组成有很大差异，说明土壤中的AM真菌对茄子黄萎病的发生有一定影响。较少

In controlling plant diseases, utilization of natural and safe microorganisms for biological control system is highly anticipated. However, this disease control system is often claimed for its inconsistent effect. Therefore, we conducted a series of experiments aiming at development of disease control systems pertaining safe and consistent efficacy for soil-borne diseases by utilizing indigenous microbial diversity. Specific results obtained in this research projects are as follows. (1)Analysis of relationships between soil-borne diseases and microbial diversity indigenous to soil : application of wild oats as a green manure, which was effective on controlling Verticillium wilt of tomato in previous pot experiments, was verified under a field condition in monitoring soil microfloral changes with PCR-DGGE, FAME, and CLPP. On the other hand, suppression of Fusarium wilt and Bacterial wilt of tomato by applying wheat-bran with irrigation, i.,e., ‘soil disinfestation with soil reduction me … More thod' was investigated in terms of pathogen densities as well as facultative anaerobic bacteria. The latter was further elucidated with identifying bacteria by cloning the DGGE bands. In addition, organic acids produced during this event were determined with HPLC. (2)Analysis of relationships between soil-borne diseases and symbiotic arbuscular-mycorrhizae (AM) diversity indigenous to soil : AM are known to protect plant from various environmental stresses as well as provision of inorganic nutrients such as phosphorus. Therefore, to elucidate the relationships between AM diversity indigenous to soil and suppression of soil-borne diseases, the AM diversity colonizing plant roots was determined using fatty acid methyl ester(FAME). Specifically, components of FAME originated from AM e.g., 16:1ω5 were compared between healthy and diseased (infected by Verticillium wilt) roots of eggplant. The results indicated that the FAME components of diseased roots substantially differed from those of healthy roots, suggesting that AM fungi indigenous to soil influences on the disease occurrence of Verticillium wilt of eggplant. Less