Submicroscopical evidence of bacterially induced resistance in tobacco leaves

Ott, Péter and Szabó, László and Klement, Zoltán and Balázs, Ervin (1997) Submicroscopical evidence of bacterially induced resistance in tobacco leaves. ACTA PHYTOPATHOLOGICA ET ENTOMOLOGICA HUNGARICA, 32. pp. 265-280. ISSN 0238-1249

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Abstract

A prototrophic HR (hypersensitive reaction)-negative mutant of Pseudomonas syringae pv. phaseolicola was used to induce the early induced resistance (EIR) and the laté induced resistance (LIR) in tobacco. This mutant alsó served as an indicator of submicroscopic hőst responses in nontreated, heat shocked, and dark-treated leaves. Heat shock (50 °C, 20 s) and dark are known to suppress EIR and LIR, respectively. Intercellular spaces ofthe non-treated and heat-shocked leaves contained dividing bacteria at 6-12 hpi. At 24-48 hpi the ratio ofdividing bacteria decreased with a concomitant increase of an intensely eleetron-dense, distorted bacterial form frequently embedded in an amorphous, eleetron-dense mátrix. Around 12 hpi paramural papillae appeared as site-specific plánt responses to the neighbouring bacterial cells. Oceurrence of papillae correlated closely with the distorted, possibly damaged bacterial form. The highest number of dividing bacteria and the largest microcolonies indicated the partial lack of EIR in heat-shocked leaves, bút neither the distorted bacteria nor papillae could be connected with EIR. In the dark, compared to the other two treatments, less distorted bacteria constituted looser microcolonies after 24 hpi, while papilla formation was suppressed. Thus a relationship was found between papilla formation, the distorted bacterial cells and LIR.

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