The suppression of the development of silicon containing deposits in french bean phaseolus vulgaris cultivar pinto leaves by exudates of the bean rust fungus uromyces phaseoli var typica and extracts from bean rust infected tissue
Physiological Plant Pathology 18(2): 149-156
Extracts of bean rust-infected French bean leaves, when injected into uninoculated French bean tissue, increased the frequency of haustoria subsequently produced by U. phaseoli var. vignae (the cowpea rust fungus); in correlation, the incidence of S-containing, electron-opaque deposits at infection sites decreased. The effect of these extracts on haustorium formation was influenced by the age of the leaves from which the extracts were made, and the age of the leaves into which they were injected. Exudates from infection structures of U. phaseoli var. typica (the bean rust fungus) also increased haustorium production by U. phaseoli var. vignae, and in general, both extracts and exudates were less effective in older French bean leaves. Such leaves also were more resistant to bean rust infection, due at least in part to the increased number of infection sites at which no haustoria developed; in these situations, there was a corresponding increase in the incidence of S-containing deposits. Injection of extracts from susceptible, infected tissue increased the incidence of haustoria produced by U. phaseoli var. typica in these older leaves. The ability of U. phaseoli var. typica to invade its host species successfully is probably initially determined by its ability to suppress the deposition of S-containing deposits, which would otherwise prevent the development of the 1st haustorium.