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

1.为了建立白菜根内生真菌毛螺旋菌（Heteroconiu chaetospira）的有效接种方法，确定了适宜的苗圃土壤和真菌定植的营养培养基葡萄糖浓度。以泥炭苔藓为生根介质时，真菌的定殖频率较高。当添加0.1%葡萄糖时，泥炭苔藓的定植率最高（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域。此处，菌丝形成细胞间或细胞内的微硬化。在温室条件下，研究了土壤湿度、pH值和病原菌静息孢子密度等不同环境条件对毛螺旋体异菌（Heteroconium chaetospira）防治棒根菌效果的影响。当病原菌静息孢子密度为10^5孢子/ g土壤时，土壤pH为7.2、6.3和5.5条件下毛毛螺旋藻处理的平均病害指数分别为0、4和6。当病原菌静息孢子密度为10^5孢子/ g，土壤含水量为40%、60%和80%时，毛毛螺旋体处理的植物表现出棍根病症状，指数分别为1、5和100。当静息孢子密度为每克土壤10 ~ 6个时，毛毛螺旋菌只有在土壤含水量为40%时才能有效抑制棒根病，这意味着该病的发病率降低了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.