Abstract
Recent publications indicate that asexual mutations in fungi occur frequently on culture media. In the present paper a distinct albino mutation by a species of Brachysporium parasitic on the rice-seedlings is reported. Brachysporium is a genus of Dematiaceae, and is characterized by dark brown mycelium and conidia. The parental form under consideration was isolated from an infected seedling of the rice plant in April, 1925. Cultures were started from single spores at that time. In October of the same year we found that from the lower portion of the slant of the apricot-decoction agar in a test tube, a sector grew out which lacked the usual color character. Subcultures were made from the contrasting area of this culture, by transferring some of the white mycelium to other culture media. The conidia produced by this albino strain correspond substantially in size and shape with those of the normal strain.
Repeated single-spore isolations have been made, and these cultures remain all constant for the character of albinism, as do the cultures made by isolating bits of mycelium. Effect of temperature on the growth of the mutant and also of the parental form has been studied. But we could not find any remarkable difference between them. The optimum temperature for the growth of them seems to lie at about 28°C. In order to ascertain whether there are any differences in degree of virulence of the mutant and its parent, comparative inoculation experiments were made on the rice seedlings. The results obtain d indicate however that they have almost the same degree of virulence. In the present paper the results of our investigations on the effect of some environmental factors to the color modifications of the albino strain on the cultures are also described.
