Studies on the Interaction between Phytophthora and other Microorganisms

(3) Association of several bacteria to the hypha of Phytophthora capsici Leon

Abstract

To elucidate the microbial succession in plant tissue rotted by Phytophthora, the association of bacteria with the surface of the hyphae of Phytophthora capsici on agar medium was studied by the opposition culture method using 16 species of bacteria, including cucumber-B₁, which was isolated from the cucumber rotted by P. capsici.
Among the 3 agar media used, the bacterial association with P. capsici occurred rapidly at 28-32C and pH 6.6 on oatmeal agar medium, which was favorable for the pathogen. Of the bacteria tested, cucumber-B¹ was associated markedly with the hyphae 24-48hrs after the opposition culture, as well as was Erwinia carotovora and other several motile bacteria.
The associated bacteria, cucumber-B₁, were always found on the surface of the hyphae except at the growing point (or apical area), and the association was better in high concentration agar medium (2%) than in lower (1.0-1.5%).
The taxis of bacteria to the hyphae of P. capsici in the bacterial suspension was studied. The taxis of E. carotovora E. aroideae, and cucumber-B₁ occurred remarkably on oatmeal agar medium; Sarcina lutea showed no taxis on agar medium. Bacterial taxis to the sterilized hyphae and glass fiber was not observed.
From this result, it is suggested that the association of bacteria with P. capsici could be established not only by an attachment or adherence by chance but also by an interrelationship between the bacteria and P. capsici, that is, the attractive phenomena due to exduation from the hyphae of the pathogen.