土壤質地對蘿蔔黃葉病的影響

Effect of Soil Texture on Disease Development of Radish Yellows

黃葉病是本省蘿蔔重要且嚴重的一種土壤傳播性痛害。為能了解土壤質地對病害發生的影響，四種不同質地包括砂土（sand），砂質壤土（sandy loam），壤土（loam）以及粘質壤土（clay loam）被用來測定。在盆缽試驗中，四種不同土壤對蘿蔔黃葉病菌（Fusarium oxysporum f. sp. raphani）之存活能力略有差異，即在未種植蘿蔔時，四種土壤間並無顯著性的差異，但當種植蘿蔔後則以壤土最不利於病原菌的存活。同時在含有較高之菌量密度（5×103 propagules/g‧soil）下，黃葉病的發生程度以壤土最低。分生胞子及厚膜胞子發芽試驗的結果亦顯示在壤土中者發芽率最少。經由土壤微生物相的分析，得知壤土之細菌含量約為砂土之十四倍，砂質壤土之八倍以及粘質壤土的四倍。

Radish yellows, caused by Fusarium oxysporum f. sp. raphani is a prevalent soil-borne disease in Taiwan. In order to understand the factors that were effected by soil texture on disease development on radish yellows. Four kinds of soil: sand, sandy loam, loam, and clay loam, were investigated on their effects on the disease incidence and the survival of the pathogen. Results showed that radish yellows could be reduced by planting in loam soil and the survival of the pathogen in loam also was the least among the soil types tested. But life span of the pathogen was of no relationship among soil textures in case of no radishes were planted. Conidium and chlamydospore germination of F. oxysporum f. sp. raphani also indicated that loam soil was less benefit to the pathogen than the other soils. Soil microflora analysis indicated that the population of bacteria in loam soil was 4 to 14 times more than that on the other three kinds of soil.