Biological Control of Brown Stem Rot of Adzuki Bean by Cleaning Crops

本研究的目的是通过清洁作物来寻找减少小豆褐腐病(BSR)的有效作物。1998年和1999年，4种绿肥作物(野豌豆、多花黑麦草、野燕麦和高粱)在不同的病原菌侵染的田里种植，次年在所有田里种植小豆。与其他作物相比，种植野燕麦的田间病害明显减轻。但病原菌种群与作物之间未发现相关关系。在所试验的绿肥作物中，野生燕麦种植区的产量高于其他作物。这些结果表明，野生燕麦最适合清理作物对小豆的BSR。为探讨野燕麦的抑病机理，对野生燕麦种植土壤中的微生物区系进行了检测。对病原菌有拮抗作用的放线菌数量约为红小豆补植土壤的13倍。种植野燕麦的土壤中病原菌孢子萌发率显著低于其他作物土壤。这些结果表明，野生燕麦土壤具有较大程度的土壤真菌抑制作用。这可能是野生燕麦抑制BSR的原因之一。在最后一年(2000年)，在自然感染BSR病原菌的农民田里检查了野生燕麦的抑制效果。农户田间病虫害显著减少，产量明显高于其他小区。从这三年的结果来看，野生燕麦是防治BSR病的最佳清洁作物，在不久的将来，燕麦将与小豆田的种植制度相结合。

The purpose of this study is to find the effective crops in reducing the Brown Stem Rot (BSR) disease of adzuki bean by the cleaning crops. In 1998 and 1999, 4 green manure crops (vetch, italian ryegrass, wild oats and sorghum) were planted in different fields infested with the pathogens and in the next year, adzuki bean planted in all fields. The disease decreased remarkably in the fields planted with wild oat compared with other crops. However, no relation was found between the pathogen population and the crops. The yields of wild oat planted plots was higher than that of any other crops among green manure crops tested. These results showed the wild oat was the most suitable for cleaning crops to BSR of adzuki beans. To find out the mechanism of the disease suppression by wild oat, the soil microflora in the wild oat planted soils weas cheked. The population of antagonistic actinomycetes to the pathogen was about 13 times higher than the adzuki bean replanting plot soils. The germination of the pathogen spores in the soils planted with wild oat was significantly lower than other crop soils. These results suggested that the wild oat soils had a greater degree of soil fungistasis. These may be one of the reasons why the BSR was suppressed by the wild oat. In the final year (2000), the suppressive effect by wild oat was checked in the farmer fields naturally infested with BSR pathogens. In the farmer fiels, the disease decreased dramatically and the yields was higher than that of other plots. From these three years results, the wild oat is best cleaning crops against the BSR disease and in near future oat will be combined among the cropping system in adzuki bean fields.