Effet du stress salin sur Verticillium albo-atrum : pathogénicité et production d’enzymes cellulolytiques in vitro

Tomato plants var Marmande are highly susceptible to infection by the Moroccan isolate P80 of Verticillium albo-atrum, yet it is slightly susceptible to the avirulent isolate P3A of the same fungus. Repeated watering of the infected plants with saline solution enriched by NaCl (80mM) induced an aggravation of Verticillium symptoms caused by the aggressive isolate and a gain of new pathogenic aptitude for the non pathogenic isolate. The effect of the salinity on the fungus developted on CMC medium produced a light decrease of the mycelial growth and a significant increase in the carboxymethylcellulase activity in vitro. The correlation of the enzyme performance under salinity stress and the pathogenecity of Verticillium is discussed