Seventy one isolate of different soil-borne fungi as well as, eight Botrytis isolates were isolated from wilted, rotten roots and spotted leaves of faba bean plants cv. Giza-716 cultivated in the three Egyptian governorates of north Delta, i.e. Minufiya, Gharbia and Kafr El-Sheikh. These isolates were identified as Rhizoctonia solani, Verticillium albo-atrum, Fusarium oxysporum, F. solani, F. semitectum and F. moniliforme. R. solani followed by V. albo-atrum were the most frequent fungi in the three governorates. The highest number of isolated fungi was recorded in Menoufya governorate followed by Kafr El-Sheikh and Gharbia governorates, respectively. Also, Botrytis isolates were identified as Botrytis fabae Sard and scored its highest number in Menoufya governorate followed by Gharbia and Kafr El-Sheikh governorates, respectively. Pathogenicity test of 18 isolates of root isolates, (represent 6 different fungi of the three governorates) revealed that all tested isolates could infect the roots of faba bean (Giza-716 cv) causing pre and post emergence damping-off and reduced the survived plants. The isolates of F. oxysporum (Isolate-2) followed by R. solani (Isolate-3), F. solani (Isolate-2), F. moniliforme (Isolate-3) and V. albo-atrum (Isolate-1) were the most virulent ones. Also, the eight tested isolates of Botrytis fabae could infect faba bean plants (cv. Giza-716) with significant differences among them. B. fabae (Gharbia isolate) was the most aggressive isolate causing chocolate spot severity.
All tested plant extracts i.e., garlic, onion and caraway have significantly reduced the linear growth of all the tested fungi with variations among the tested plant extracts. Garlic extract was the most effective plant extract followed by onion and caraway. On the other hand, using antagonistic bio-agents in vitro reduced significantly the linear growth of all examined fungi, where T. koningii and T. harzianum were the most effective bio-agents followed by B. subtilis. Scanning electron microscope (SEM) of the interaction sites between Trichoderma harzianum and the pathogenic fungi revealed different types of parasitism in the form of coiled hyphae, pincer shaped hyphae, hook and pincer shaped hyphal branches, hooked parallel hyphae looking for penetration, ring hyphae and adhesive shaped hyphae as well as appressorium-like bodies as cleared in cases of R. solani, F. oxysporum and B. fabae. All tested fungicides, in vitro indicated that increasing concentrations of the tested fungicides have gradually decreased the fungal linear growth of the tested pathogenic isolates. All pathogenic fungi were sensitive to Benlate, while, V. albo-atrum was sensitive to Vitavax 200, while, F. moniliforme was sensitive to Rizolex-T and Monceren. Meanwhile, all the tested fungicides at all the tested concentrations affected significantly the growth of B. fabae, where Dithane-M45 was the most effective fungicide followed by Benlate and Copper Acrobat respectively.
Key words: faba bean, soil-borne fungi, chocolate spot, plant extracts, bio-agents, bio-agents and fungicides
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