INDUCTION OF DEFENSE RESPONSES IN FABA BEAN PLANTS AGAINST CHOCOLATE SPOT DISEASE CAUSED BY BOTRYTIS FABAE USING CHITOSAN

Chocolate spot disease caused by Botrytis fabae is a major problem that limits faba bean production in Egypt. The in vitro antifungal activity of chitosan and its ability to elicit defense responses in two faba bean cultivars Giza 416 (resistant) and Giza 40 (susceptible) against this fungus were evaluated. Seven isolates of B. fabae were cleaned from infected leaves. All isolates were pathogenic to Giza 40 cultivar, with isolate 3 (Bf-3) was the most virulent. Chitosan inhibits the mycelial growth of B. fabae (Bf-3) in concentration-dependent manner. At 0.75 % and 1 %, chitosan completely inhibits the growth of B. fabae. Under greenhouse conditions, two fab bean cultivars, Giza 416 (resistant) and Giza 40 (susceptible) were sprayed with 0.5% chitosan. Treatment with chitosan 0.5% reduced the chocolate spot disease severity for both cultivars compared with untreated infected control. Plants of both cultivars treated with chitosan showed a lower rate of lipid peroxidation and higher levels of chlorophyll and total phenols compared with untreated infected control. Chitosan stimulated the activity of defense enzymes such as peroxidase (POD), polyphenol oxidase (PPO), and phenylalanine ammonia-lyase (PAL). Furthermore, chitosan treatment increased the expression levels of three pathogenesis