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

1.为建立根内生真菌Heteroconiu chaetospira侵染大白菜幼苗的有效方法，确定了适宜的苗圃土壤和葡萄糖浓度。当泥炭藓被用作生根培养基时，真菌以高频率定殖。当泥炭藓用0.1%葡萄糖修正时，定殖率最高（75%）。在这些条件下，真菌菌丝在根皮层细胞内发育。相反，在高葡萄糖条件下，真菌定植主要限于表皮或皮层根组织的细胞间区域。在温室条件下，研究了不同环境条件（包括土壤湿度、pH值和病原菌休眠孢子密度）对内生真菌毛旋异锥菌（Heteroconium chaetospira）防治根肿病效果的影响。当病原菌休眠孢子密度为10^5个孢子/克土时，平均病情指数为10.5%; pH7.2、6.3和5.5条件下处理的土壤中，毛螺旋体的最大生物量分别为0、4和6。当土壤含水量为40、60和80%时，病原菌休眠孢子密度为10^5个/g土壤时，H.毛螺旋体处理的植物表现出根肿病症状，指数分别为1、5和100。当休眠孢子密度>10 ~（-6）/g土壤时，H.只有在土壤含水量为40%时，毛螺旋体才能有效地抑制根肿病，这代表病害减少了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.