| Research Abstract |
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.
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