Histological studies of resistance to soybean rust, Phakopsora pachyrhizi Syd

Abstract

Histological comparisons were made of susceptible, resistant, and immune responses of soybean to infection by rust, Phakopsora pachyrhizi, at intervals after inoculation. In the susceptible host there was extensive hyphal growth and vigorously sporulating uredia developed. The immune hosts showed no macroscopic symptoms of infection, but at the microscopic level exhibited a hypersensitive response which was limited to a few cells. In the resistant host the hypersensitive response was not as limited, fungal development and associated host cell necrosis were more extensive, and symptoms of infection were visible macroscopically.