蘿蔔黃葉病菌在發病田中之分佈與消長

Abstract

蘿蔔黃葉病菌(Fusarium oxysporum (sch1.) f. sp. raphani Kend.et Snyd.)於罹病田中，大部分垂直分佈於0-30 cm深的土中，而在整塊田中病原菌則成均勻分佈。在輪作地區（新社水井）病原菌之密度變化隨著作物的不同而呈不規則狀。在連作區（埔里太坪頂）則因耕作單純，菌量隨著蘿蔔的種植而升高；反之隨著休耕期的增長而密度逐慚下降。在罹病田中，多種雜草如野莧、馬齒莧、細柄黍等之根部可被本菌纏化(colonization)。因之本菌亦可因此等雜草之存在而增加其存活率。種植青椒亦可增加本菌之存活，但水稻及甘藍却能降低黃葉病菌之存活。 Field survey revealed that the radish yellows pathogen, Fusarium oxysorum f. sp. raphani, frequently existed in 0-30 cm deep of soil, and was evenly distributed in the diseased field. In continuous monoculture fields of radish the population of the pathogen. in soil tended to be positively correlated with the history of cultivation, in case of crop rotation, the survival curve was irregular. The pathogen was found to survive in the rhizospheres of various weeds and could colonize their roots, therefore, longevity of the pathogen in soil could be lengthened by the presence of weeds. Planting of nonsusceptible crops such as pepper also favored its survival in soil, but planting of rice, cabbage and knot grass (Pospalum distichurn) resulted in decreasing the population of pathogen in soil.