Multiplication Of Xanthomonas Campestris Pv. Vesicatoria In Plant Tissues And Associated Changes In Membrane Permeability

Azzeddin M.Y. Alawami
department of Pant Protection, Faculty of Agriculture, Omar Al-Mukhtar University, El-Beida, Libya.
E-mail: Azzawami2002@yahoo.com

Abstract

The multiplication of the bacterium Xanthomonas campestris pv. vesicatoria, the causal organism of tomato spot disease, in plant tissues and the associated changes in permeability of cell membranes as a response to infection was evaluated. The results showed that the pathogen starts to multiply in the tissue of the susceptible host (cv. Rio-Grande) directly without any lag phase. However, a lag phase was recorded in the tissue of the resistant cv. Marmande. On the other hand, the pathogen was able to induce the typical disease symptoms only on tomato plants (cv. Rio-Grande). In non-host tissues (Tobacco) the level of multiplication decreased greatly from the second day and remained low until the end of the test. Population of the saprophytic bacterium Pseudomonas flourecense in tomato plant tissues (cv. Rio- Grande) decreased at a low rate within the first 24 hours. The rate of increase in electrolyte leakage (as an increase in permeability) in susceptible host tissues three days after inoculation was almost 50% of that in resistant cultivar. However, six days later the reverse was true. In non-host tissue, electrolyte leakage was high at the beginning but dropped continuously to be less than in the other tissue types. The saprophytic bacterium, on the other hand, caused very little permeability changes in tomato tissues.