The Effects of Light, Pyridoxine and Biotin on the Development of the Mycoparasite, Gonatobotryum Fuscum

Abstract

The inhibitory effects of light on the development of Gonatobotryum fuscum on its host, Graphium sp., has been attributed to the destruction by light of vitamin B₆, which is required for growth and other metabolic activities of the host. Pre-inoculation exposure of 4 days at 300 ft-c of white light rendered the medium unsatisfactory for growth of the parasite on its host, even in darkness, unless Bo was again added. A higher concentration of B₆ is required for development of the parasite than for growth of the host. However, the addition of biotin, which has no visible effect on growth of Graphium sp., allows the development of the parasite on its host, even on media having a low concentration of B₆. The conclusion is reached that biotin is essential for the synthesis by the host of a nutrient required by the parasite. Using Sordaria fimicola as an assay fungus, it was shown that the amount of biotin synthesized by Graphium sp. was correlated with the amount of B₆ in the medium. Evidence is presented that G. fuscum synthesizes and excretes vitamin B₆.