Abstract
Surveys for faba bean chocolate spot disease covering 6 districts in Delta of Egypt were conducted. Out of these surveys, six isolates of the pathogen were obtained and purified using single spore technique. These isolates were identified as Botrytis fabae. All isolates were subjected to pathogenicity tests to determine the most aggressive one. All isolates appear to have the potency to cause chocolate spot disease, but the isolate from Sherbin was considered to be the most aggressive one and was selected for further studies. In vitro, the effect of provided phenolic compounds on inhibition of mycelia growth and the growth rate of B. fabae was investigated and arranged as follows: salicylic acid > Shikimic acid > shikimic acid+salicylic acid, as compared to control values. Furthermore, significant reduction in the disease incidence (%) and severity (%) were recorded in faba bean plants treated with salicylic acid followed by shikimic acid then their interaction. Botrytis fabae infection caused noticeable increase in the activity of defense enzymes (i.e., peroxidase, polyphenol oxidase and phenyl alanine ammonia lyase) in infected faba bean plants. In the majority of cases, the applied phenolic compounds induced additional increase in such enzymes than that sprayed with fungicide. This increment was concomitant with the increase in the endogenous total phenols, shikimic acid and salicylic acid content. In addition, the most effective treatment in enhancement faba bean resistance against B fabae infection was salicylic acid at 0.7 mM
Highlights
The faba bean (Vicia faba L.) is considered as one of the most profitable field crops in Egypt
Peroxidase functions in the metabolism of Reactive Oxygen Species (ROS) and Reactive Nitrogen Species (RNS), activating the Hypersensitive Response (HR), a form of programmed cell death at the infection site that is associated with limiting pathogen development [3]
The present results showed that, the activity of phenylalanine ammonia lyase activity (PAL) was increased with infection by B. fabae (Table 4)
Summary
The faba bean (Vicia faba L.) is considered as one of the most profitable field crops in Egypt. The faba bean is susceptible to attack by many diseases, such as chocolate spot disease caused mainly by Botrytis fabae and diseases are responsible for considerable losses in seed yield [2]. Peroxidases oxidize phenols to quinines, which are toxic to pathogens. Peroxidase functions in the metabolism of Reactive Oxygen Species (ROS) and Reactive Nitrogen Species (RNS), activating the Hypersensitive Response (HR), a form of programmed cell death at the infection site that is associated with limiting pathogen development [3]. Polyphenol oxidases participate in the oxidation of aromatic substrates and dihydroxyphenolic compounds in the presence of oxygen in host tissues, producing quinones that are toxic to pathogens [4]
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