Development of hyphal sheaths in Bipolaris maydis race T

Abstract

Light microscopic studies of Bipolaris maydis race T demonstrated that a fibrillar sheath, often several times the hyphal diameter, can be observed when the hyphae are negatively stained with India ink or treated with fluorescent antibodies or diaminobenzidine. Sheaths were observed on hyphae incubated under a variety of cultural conditions and on race O of B. maydis as well as on other species of Bipolaris. Sheaths were found only on rapidly growing hyphae such as tips and germ tubes; conidia and hyphal segments older than approximately 72 h lacked a sheath. Examination of the hyphae using electron microscopy confirmed the age-dependent nature of the sheath and suggested that the lack of this structure on old hyphae is due to the deposition of a pellicle on the hyphal surface.