Some aspects of transmission and electron microscopy of necrotic leaf spot of aspen

摘要

Continued studies on the necrotic leaf spot disease ofPopulus tremuloidesMichx. and related hybrids have verified transmission of the causal agent by grafting and demonstrated its passage through seed. Attempted transmissions by mechanical means to a wide variety of herbaceous hosts were negative except for extracts from two hybrids which induced necrotic spots onVigna sinensiscv. Black Eye.Some aspects of disease development were revealed by electron microscopy. Attempts to visualize a causal agent were not successful but occasional virus-like aggregates were observed.