otrytis blight was observed in Egypt (Nov., 2016) on Poinsettia (Euphorbia pulcherrima) that caused small light brown spots at the edge of leaves and enlarged to include the whole leaf. The isolated fungus was identified as Botrytis cinerea based on its morphological and cultural characteristics. In greenhouse, artificial inoculation of plants developed blight symptoms. The effect of ultrasonication on the particle size of lemongrass and citronella essential oil nanoemulsions was determined. The results showed that the particle sizes from sonication for 30 minutes were around 90.6 and 79.8 nm, and TEM study revealed the spherical shape. Changes in the essential oil emulsions components were observed in the nanoemulsions compared with the original as the size of the oil particles become small, the stability and main component of the emulsion were significantly improved. In vitro, the nanoemulsion at different concentrations (1000-8000 ppm) were capable of adversely affecting the mycelial growth of Botrytis cinerea. In greenhouse experiment, poinsettia plants were sprayed with the two essential oils (emulsion and nanoemulsion) and the fungicide carbendazim 50% WP (as additional control), after and before inoculation by the fungus. The disease severity was decreased by the treatments compared to the untreated control. The lowest disease severity, being 10.0 and 13.0% with nanoemulsion of lemongrass, before and after inoculation by the fungus, respectively. The results indicate an increase in the concentrations of active substances in essential oils due to their exposure to ultrasonication and their conversion to nanoemulsions, as the results suggest the potential effects of lemongrass essential oil nanoemulsion as a novel fungicide agent against Botrytis cinerea.
usarium wilt of cumin (Cuminum cyminum L.) caused by Fusarium oxysporum f. sp. cumini is a destructive disease, responsible for pre-mature plant death leading to serious economic losses in all cumin-growing areas in Middle and Upper Egypt. The fungus was isolated from the four surveyed governorates (Beni-Sueif, Minia, Assiut and Fayoum). Pathogenicity tests showed that the isolates obtained from Matai County followed by those from Beni Mazar, Minia governorate were the most aggressive and showed the highest frequencies (%) compared to other isolates. Efficiency of some biocides namely Bio-Cure-F (Trichoderma viride, 2x10 6 spore/cm 3 ), Bio-Cure-B (Pseudomonas fluorescens, 1x10 8 spore/cm 3 ) and inducer resistance chemicals (chitosan, kinetin and salicylic acid) either individually or in combinations was evaluated in controlling the disease in the greenhouse. Combined treatments between bioagents and the tested elicitors were more effective in reducing the disease incidence than using each treatment alone. P. fluorescens combined with chitosan was the superior treatment in this respect.
Organic solvent extracts of lemon grass leaves were more effective than those of rhubarb roots in inhibiting mycelial growth of F. solani and R. solani , two fungi pathogenic to pothos plants causing root and basal stem rots. Superiority was realized as for ethanolic extracts than those extracted using hexane and ethyl acetate as organic solvents. Dipping root system of pothos cuttings in 20 % concentration of ethanolic extracts of lemon grass or rhubarb for 15 min. just before planting in soil infested with either of F. solani and R. solani recorded the lowest percentages of diseases incidence by (5 % & 10 %) and (15 % &20 %) , respectively , relative to those of their controls (40 % & 60 %). Values of physical characteristics of lemone grass essential oil such as specific gravity (0.89 %) , optical rotation (-1.6) , refractive index (1.4875) and acid number (8.3) were estimated. Also , chemical main compounds quantitatively determined by chromatography which confirmed that volatile matter of lemon grass oil represents 100 % of its composition. However , citral and myrecene constituted 77.0 % and 6.5 % of the total composition of that oil. Lemon grass essential oil at concens. of 10 % and 20 % could completely inhibit mycelial growth of the aforementioned two fungi , respectively .Besides , citral (2.5 concen.) realized the same effect , whereas, myrecene only minimized mycelial growth of these fungi by 40% and 28.6 % .
Surface and non-surface sterilized seeds of commercial cotton cultivars were examined for qualitative and quantitative estimates of seed-borne fungi. Aspergilus flavus, A.niger and Alternaria alternata were the most dominant species isolated. Cultivar and cultivar treatment interactions were very highly significant source of variation in frequencies of fungi. Both cultivar and cultivar x treatment interactions contributed most to the variation in frequencies of the isolated fungi. The effect of surface sterilization on frequencies of fungi isolated from seeds varied depending on the cultivar used. Giza 85 cultivar yielded the lowest number of fungi (5 fungi). Other cultivars yielded a number of fungi ranging from 7 to 13. The role of seed borne fungi in cotton seedling disease incidence was more evident in the post-emergence stage compared with the pre-emergence stage. Also, Cluster analysis divided the cotton cultivars into two distinct groups, one group consisting of 6 cultivars (Giza 45,Giza 70,Giza 85,Giza88,Giza89 and Giza90) and a second group consisting only one cultivar Giza90.Constructed regression models showed that difference in seedling disease variables were due largely to the effects of A. alternata, Cladosporium spp. and Fusarium semitectum .
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