GROWTH OF THE RUST FUNGUS PUCCINIA HELIANTHI ON TISSUE CULTURES OF ITS HOST

Abstract

Rust-infected cotyledon, hypocotyl, and stem sections of sunflower seedlings were cultured on nutrient agar media. Callus growth from cotyledon sections was negligible, but hypocotyl and stem sections proliferated more or less freely. Infections arising from basidiospores produced an abundant tuft-like growth of haploid surface mycelium. Infections arising from urediniospores lacked almost entirely surface mycelial growth, but produced urediniospores in abundance, and finally teliospores.Copious aeciospore production occurred in some cultures where two basidiospore infections of different mating types coalesced. Later such compound infections produced urediniospores and teliospores. Tufts of mycelium developed on the new callus growth of some cultures. One of these calluses (examined cytologically) contained a number of more or less subnormal pycnia and aecia in different stages of development. Only a few sections produced callus tissue capable of surviving repeated subculturing. In the fourth set of subcultures from one such section, rust mycelium appeared as tufts on six of the calluses.