Development of the biopesticide for control of some soil-borne plant pathogens by new fungal root endophyte

1.为了建立一种高效的接种大白菜根际内生真菌毛壳异尖线虫的方法，确定了适合大白菜定植的苗圃土壤和葡萄糖浓度。以泥炭苔藓为生根基质时，真菌定植频率较高。0.1%葡萄糖对泥炭苔类植物的定殖率最高(75%)。在此条件下，真菌菌丝在根皮质细胞内发育。相反，在高糖条件下，真菌的定植主要局限于表皮或皮质根组织的细胞间区。在温室条件下，研究了土壤水分、土壤pH值、病原菌休眠孢子密度等不同环境条件对内生真菌毛状异孢子菌生物防治丛枝菌根瘤病的影响。当病原菌休眠孢子密度为每克土壤10 5个孢子时，在土壤pH为7.2、6.3和5.5条件下处理的平均病情指数分别为0、4和6。当病原菌休眠孢子密度为每克土壤10 5个孢子，土壤含水率分别为40%、60%和80%时，毛壳螺杆菌处理植株表现出丛枝症状，指数分别为1、5和100。当休眠孢子密度为每克土壤10-6个孢子时，毛细螺旋体仅在土壤水分含量为40%时才能有效地抑制根瘤病，这意味着该病减少了75%。

1.To develop an efficient method to inoculate Chinese cabbage seedling with the root endophytic fungus Heteroconiu chaetospira, an appropriate nursery soil and glucose concentration for the nutrient medium for fungal colonization were determined. The fungus colonized at high frequencies when peat moss was used as the rooting medium. Colonization was highest (75%) when peat moss was amended with 0.1% glucose. Under these conditions, fungal hyphae developed intracellularly in root cortical cells. In contrast, under high glucose conditions, fungal colonization was restricted mostly to intercellular regions of epidermal or cortical root tissues. Here, hyphae formed inter-or intracellular microsclerotia.2.The effects of varying environmental conditions, including soil moisture, soil pH, and pathogen resting spore density, on the effectiveness of the biological control of clubroot by the fungal endophyte Heteroconium chaetospira was evaluated in greenhouse. When the pathogen resting spore density was 10^5 spores per gram of soil, the mean disease index in the H. chaetospira treatment at a soil pH of 7.2,6.3 and 5.5 conditions were 0,4, and 6, respectively. When the pathogen resting spore density was 10^5 spores per gram of soil with 40,60, and 80% soil moisture content, H. chaetospira-treated plant displayed symptoms of clubroot with indices of 1,5, and 100, respectively. When the resting spore density was >10-6 per gram of soil, H. chaetospira effectively suppressed clubroot only at a 40% soil moisture content, which represented a 75% reduction in the disease.