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 bioagents
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. |
