Pathogenicity to Pumpkins (Cucurbita spp.) of Bottle Gourd Fusarium Wilt Organism (Fusarium oxysporum f. sp. lagenariae) Isolated from Acutely Wilted Cucurbitaceous Plants

Abstract

Acute wilting of watermelons grafted on pumpkin rootstocks first occurred in plastic greenhouses in Kumamoto Prefecture in 1977. A fungus was isolated from the grafted tissues of the plant, being identified to be Fusarium oxysporum f. sp. lagenariae Matuo et Yamamoto, the pathogen of Fusarium wilt of bottle gourd (Lagenaria siceraria). This pathogen also infected Cucurbita ficifolia and C. maxima of pumpkin plants, although no infection was found on C. moschata, C. pepo and C. maxima×C. moschata. The symptoms of the infected C. ficifolia and C. maxima appeared as follows: the cotyledons became yellow and wilted at the early growing stage, and the foliage leaves soon wilted from the lower position after having become yellow. The growth of wilting plants gradually declined, followed by death finally. The roots of the diseased plant were poor and their root surface became brown. The pathogen was isolated from pieces of the stem tissues with browned vascular bundles in a high rate. This disease is proposed naming as ‘Fusarium wilt of pumpkin’.