Physiology of the causal fungi of stem rot of rice plant

(II) On the growth factors

Abstract

It this paper, the results of the experiments on the growth factors of rice stem rot fungi (Leptosphaeria salvinii Catt. and Helminthosporium sigmoideum var. irregulare Cralley et Tullis) are noted. These fungi made no growth on the synthetic media, composed of sugar and inorganic salts, but good growth was obtained by adding rice straw decoction which seemed to contain growth factors. It was demonstrated that Biotin and Thiamine were essential for the growth of these fungi. Glutamic acid, aspartic acid, glutamine and asparagine are shown to serve for accessory growth factor as well as excellent nutrient source. The adequate amount of the main growth factors were as follows: Biotin 0.001γ/cc for Leptosphaeria fungus, 0.005γ/cc for Helminthosporium and Thiamine 1.5γ/cc for both fungi. But the optimum of the accessory growth factors are not yet determined. In general, mono-amino-dicarboxylic acid had a growth promoting effect, while mono-amino-monocarboxylic acid a little or no. Alanine seemed to inhibit the growth of the two fungi tested. Pyridoxin nicotinic acid, riboflavin, inositol and pantothenic acid which have been reported to be the growth factors for many other fungi, had shown no growth promoting effect in the present experiment.