Carnation-Pseudomonas caryophylli interaction. Population dynamics of P. caryophylli and other bacteria in carnation leaves and cultured cells.

Bacterial multiplication was studied after inoculation of leaves and cultured cells (calli and cell suspension cultures) of carnation cv. Corrida with compatible (Pseudomonas caryophylli NCPPB609 and Erwinia chrysanthemi NCPPB453), incompatible heterologous (P. syringae pv. syringae B452 and pv. tomato NCPPB3310) and saprophytic (P. fluorescens PVF121) bacteria. Only P. caryophylli was able to colonize carnation leaves under the conditions of the experiment (28°C days and 14°C nights, 14 h photoperiod, 85% RH) and to induce leaf wilting. E. chrysanthemi showed very poor growth and produced only yellowing of inoculated leaf tissue. P. fluorescens survived but did not increase in number. P. syringae pv. tomato and pv. syringae declined rapidly throughout the sampling period (7 days). Nevertheless pv. syringae induced sporadic necrotic spots; and with a temperature regime of 33°C days/22°C nights, pv. tomato induced symptoms similar to those produced by P. caryophylli. However, pv. tomato was not found to provide cross-protection against P. caryophylli in dual inoculation experiments on carnation calli. Inoculations on calli and in cell suspension cultures generally confirmed the in vivo results. Tests with various filtrates of cell suspension cultures revealed that P. caryophylli favoured the release of nutrients from the plant cells, and that these cells probably produced a bacteriostatic or bactericidal substance(s).