Ecologic and Taxonomic Studies on Pythium as Pathogenic Soil Fungi

XI. Water-soaked and Spreading Lesions on Squash Hypocotyls treated with Sodium diethyldithiocarbamate

Abstract

Amakuri squash seedlings were cultivated in Hoagland solution in plant growth chamber, and water-soaked spots and spreading lesions were described on Pythium-infected hypocotyls when the seedlings were pre-treated with sodium diethyldithiocarbamate (NaDEDC) in relation to increase in host susceptibility. A slight abnormal elongation of the growth of the seedlings was found both in plant growth chamber and in water culture. Browning spots were formed in both soil and solution-grown seedlings after inoculation. The nutrient solution did not give any effect on the mycelial growth of the pathogen. The cell sap expressed from hypocotyls treated with NaDEDC did neither stimulate nor inhibit the fungal growth. Water-soaked lesions were found without any phytotoxicity when pre-treated with ether for 20-120 seconds. Only NaDEDC and sodium fluoride were considered good among the metabolic inhibitors used which induced water-soaked lesions because of the absence of phytotoxicity and stimulative effects on the fungal growth. Cuttings of the seedling which were supplied with the NaDEDC through their cut ends did not exhibit browning spots but rather formed water-soaked lesions. The water culture was more desirable method with NaDEDC than the injection in obtaining plant materials with water-soaked lesions.