The Saprophytic Status of Fusarium oxysporum Schl: Causing Vascular Wilt of Oil Palm

The droplet plating method described, especially when used inconjunction with a baiting technique, facilitates the demonstrationof Fusarium oxysporum in soil. This fungus was present in soilfrom wilt-free areas of oil palm plantations as well as in soilabout wilt-diseased palms. Hyphal fusions between soil isolatesand isolates from wilted palms could be demonstrated. The funguspersisted for periods of at least ¹ year in naturally infestedsoils under a variety of moisture conditions; it also survivedin inoculated alien soil forms of Ieast ¹year. Soil forms ofthe fungus had a high competitive saprophytic ability, competitivelycolonizing sterilized soils and sand, and organic materialsadded to soils and mixed cultures. The pathogenic isolate, aswell as the soil isolates, exhibited characters belonging tosoil-inhabiting fungi, namely continued persistance in soil:tolerance, in respect of growth and reproduction, to antagonism:and the ability competitively to colonize dead organic materialin soils. The pathogenic form is considered to be a soil inhabitant.