Growth of the rust fungus Cronartium ribicola in tissue cultures of Pinus monticola

Abstract

Cambial explants of western white pine, Pinus monticola, infected with Cronartium ribicola, were cultured on a medium containing glucose, calcium nitrate, magnesium sulfate, potassium phosphate (monobasic), ammonium sulfate, ferric sulfate, manganese sulfate, and one of three auxins: indoleacetic acid (IAA), naphthaleneacetic acid (NAA), or 2,4-(dichlorophenyoxy)acetic acid (2,4-D).Invasion of newly formed callus tissue by the rust fungus was generally slow. Dense, feltlike aerial mycelia were frequently produced. Intercellular mycelia and intracellular haustoria were typical, and direct attachments to aerial mycelia were observed. Occasionally, mycelia invaded the medium, but did not become independent of the host tissue. Typical pycnia- and aecia-like sori were produced in many cultures. Aecia-like sori formed immediately after maturation of pycnia, but did not produce spores.