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  • Author or Editor: Z. A. M. Baka x
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Seed samples of four Egyptian broad bean cultivars were tested for seed-borne fungi. The deep freezing method was used to isolate twelve seed-borne fungi viz., Alternaria alternata, Aspergillus flavus, A. niger, Botrytis fabae, Cladosporium cladosporioides, Fusarium oxysporum, F. solani,, Penicillium italicum, Rhizoctonia solani, Rhizopus stolonifer, Stemphylium globuliferum and Trichothecium roseum from the broad bean cultivars viz., Giza 3, Giza 429, Giza 843 and Misr 1. Aspergillus flavus, Botrytis fabae, Fusarium oxysporum and Penicillium italicum were the most predominant fungal species. Aqueous extracts from five wild medicinal plants (Asclepias sinaica, Farsetia aegyptia, Hypericum sinaicum, Phagnalon sinaicum, and Salvia aegyptiaca) which were collected from the Sinai Peninsula, Egypt were tested against the predominant fungal pathogens. All the aqueous plant extracts significantly inhibited the mycelial growth of these fungi, but the extract of Asclepias sinaica exhibited the strongest antifungal activity. The maximum seed germination rate was observed in infested Giza 843 and minimum in Misr 1. Treating seeds with plant extract of Asclepias sinaica (10%) enhanced the percentage of seed germination of all cultivars in both laboratory and pot experiments. Maximum root and shoot lengths of seedlings were recorded in Giza 843 during fungal infestation or treatment by plant extract. In greenhouse experiment, the aqueous A. sinaica extract reduced disease severity and total pigments but increased total phenolics and fruit yield.

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Ultrastructural investigations of the effect of lithium chloride on Botrytis fabae and its host, Vicia faba are described. Five concentrations (1, 3, 5, 7, 9 mM) of lithium chloride are chosen in the study. The results indicate that the chlorophyll content of host leaves is not affected at lower concentration (3 mM), whereas the higher concentration (9 mM) decreased the chlorophyll content. These two concentrations caused a pronounced cellular disorganization of B. fabae that ranged from disruption of the wall to marked cytoplasmic degeneration. Inoculated host leaves with B. fabae led to the appearance of more vacuolated cytoplasm, a disorganized membrane system of chloroplast and an increase in number of plastoglobuli. These observations are similar to those of host cells treated with 9 mM of lithium chloride. Host cells are not affected by the concentration of 3 mM. Ultarstructural studies indicate that the lower concentration of lithium chloride can be used as a safe fungicide to control B. fabae without a harmful effect on the host (V. faba).

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The effect of benomyl as a fungicide on growth rate and ultrastructure of two isolates (P623 and P1319) of Phytophthora infestants is compared. Using different concentrations (50, 100, 200 and 500 ppm) of benomyl caused an inhibition of the mycelial growth of both isolates depending on the degree of concentration. The isolate P1319 was found to be more sensitive to benomyl than the isolate P623. Ultrastructural studies confirmedthese observations. The hyphae of isolate P1319 subjected to 100 and 500 ppm benomyl showed severe changes in the cítoplasm more than isolate P623. The increase of lipid bodies and vacuoles in hyphal cytoplasm of both isolates was the characteristic phenomenon after treatment of benomylparticulary at the concentration of 500 ppm.

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