Induction of defense responses in faba bean plants against chocolate spot disease caused by botrytis fabae using chitosan

الملخص EN

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 related (PR) genes including PR1, PR2 (β-1, 3-glucanase), and chitinase.

The resistant cultivar (Giza 461), whether treated or untreated with chitosan displayed weaker symptoms, and enhanced values for all physiological and molecular responses than the susceptible cultivar (Giza 40).

The findings show that chitosan has a high potential for protecting faba bean plants from B.

fabae by regulating biochemical, physiological and molecular responses in faba bean plants under infection