Papers by Ludmilla Ibrahim
Horticulturae
In natural systems, plant–endophyte interactions are important for reducing abiotic and biotic st... more In natural systems, plant–endophyte interactions are important for reducing abiotic and biotic stresses in plants by producing a variety of metabolites that protect plants from pathogens and herbivores. Biocontrol strategies are increasingly being used as a viable alternative to chemical pesticides. Entomopathogenic fungi (EPF) are one of them, and they have been touted as a successful method for biological pest control in plants. Because EPF strains are sensitive to environmental conditions when sprayed, the recently discovered endophytic behavior of several EPF strains has improved their management. Cucumber mosaic virus (CMV) is one of the most common and serious plant viruses worldwide, infecting over 1200 plant species and being spread by more than 80 aphid species. CMV control is directed towards the use of chemical insecticides to eradicate its insect vectors. Endophytic EPF is currently being studied to control plant virus infection, and antagonistic effects have been report...
Lebanese Science Journal, Jun 28, 2020
Tuta absoluta is a leaf miner pest devastating tomato production. Use of broadspectrum pesticides... more Tuta absoluta is a leaf miner pest devastating tomato production. Use of broadspectrum pesticides to control this pest leads to the development of insecticide resistance, food contamination, poor health and environmental pollution. Recent knowledge of entomopathogenic fungi colonizing plants and, thus, antagonizing insect pests and plant diseases, sparked appreciable enthusiasm in using these capabilities. Therefore, this study aimed to assess the abilities of entomopathogens to endophytically colonize tomato plants, and to determine the ability of fungal species to modulate the behavior of T. absoluta. The two inoculation procedures (seed treatment and direct injection) allowed Metarhizium anisopliae and Beauveria bassiana strains to endophytically colonize tomato plants and thus have influenced the preference of T. absoluta oviposition. In Beauveria-and Metarhizium-colonized leaf mesophyll, damage by T. absoluta was significantly lower compared to control plants. This was attributed to the reduced number of eggs (7-8 plant-1) on fungus-colonized plants as opposed to 19 plant-1 on control plants in seed-treated assay. Reduced size of mines in Beauveria-injected plants has also contributed to the decrease in damage area by leaf miner larvae. The outcomes of this study suggest that seed inoculation is an effective method to be adopted by plant nurseries for commercial production of pre-colonised with entomopathogenic endophytes tomato plantlets.
Elucidation of underlying mechanisms of pathogenesis in the entomogenous fungus Metarhizium anisopliae
EThOS - Electronic Theses Online ServiceGBUnited Kingdo
Chemical composition and antimicrobial activities of essential oil and its components from Lebanese Origanum syriacum L
Journal of Essential Oil Research, 2012
The chemical composition of essential oils isolated by hydrodistillation from the aerial parts of... more The chemical composition of essential oils isolated by hydrodistillation from the aerial parts of cultivated and wild Origanum syriacum were analyzed by gas chromatograph (GC) and GC/mass spectrometry (GC/MS). Regardless of growing habitat, both oils were characterized as carvacrol/γ-terpinene chemotypes. High in vitro antimicrobial activities of essential oil were attributed to the high content of phenolic derivative such as carvacrol. Total inhibition of fungal growth was achieved at 0.25–0.50 μL/mL of essential oil. Bacteria on the other hand, were slightly more susceptible to the essential oil with minimal inhibitory concentration (MIC) ranging from 0.15 μL/mL to 0.50 μL/mL. Carvacrol and thymol were the most detrimental compounds towards both bacterial and fungal microorganisms with inhibition concentration at 50% (IC50) ranging between 0.01 and 0.18 μL/mL for bacteria and with total inhibition of fungal growth at a range of concentrations between 0.25 and 0.75 μL/mL. Antimicro...
Chemical composition and antimicrobial activities of essential oil and its components from Lebanese Origanum syriacum L
Journal of Essential Oil Research, Jul 9, 2012
ABSTRACT The chemical composition of essential oils isolated by hydrodistillation from the aerial... more ABSTRACT The chemical composition of essential oils isolated by hydrodistillation from the aerial parts of cultivated and wild Origanum syriacum were analyzed by gas chromatograph (GC) and GC/mass spectrometry (GC/MS). Regardless of growing habitat, both oils were characterized as carvacrol/γ-terpinene chemotypes. High in vitro antimicrobial activities of essential oil were attributed to the high content of phenolic derivative such as carvacrol. Total inhibition of fungal growth was achieved at 0.25–0.50 μL/mL of essential oil. Bacteria on the other hand, were slightly more susceptible to the essential oil with minimal inhibitory concentration (MIC) ranging from 0.15 μL/mL to 0.50 μL/mL. Carvacrol and thymol were the most detrimental compounds towards both bacterial and fungal microorganisms with inhibition concentration at 50% (IC50) ranging between 0.01 and 0.18 μL/mL for bacteria and with total inhibition of fungal growth at a range of concentrations between 0.25 and 0.75 μL/mL. Antimicrobial activities of α-terpinene, p-cymene and β-caryophyllene were comparable with the activities of crude oil extract against almost all microorganisms. p-cymene, however, stimulated mycelial growth of Metarhizium anisopliae.
Ophrys omegaifera SUBSP. gharifensis (ORCHIDACEAE), A NEW SUBSPECIES FROM LEBANON
- A new subspecies, Ophrys omegaifera subsp. gharifensis K. Addam & M. Bou-Hamdan, from Lebanon i... more - A new subspecies, Ophrys omegaifera subsp. gharifensis K. Addam & M. Bou-Hamdan, from Lebanon is described and illustrated. Morphologically this subspecies closely resembles Ophrys omegaifera H. Fleischm. group and in particular Ophrys omegaifera H. Fleischm. subsp. israelitica (H. Baumann & Künkele) G. & K. Morschek but differ in floral details, such us: bigger flowers that diverge from the stem at almost 90º and have macula (mirror) characterised by two bright yellow, symmetrical, ovoid-shaped, concave patterns that vary in size. Plants seem to be shorter with inflorescences typically carrying one, rarely, four flowers
In order to determine the effects of nutrition on underlying mechanisms of attenuation of the ent... more In order to determine the effects of nutrition on underlying mechanisms of attenuation of the entomogenous fungus Metarhizium anisopliae, a series of in vitro and in vivo studies were undertaken. Nutritional composition of culture media influenced germination, growth, conidiation, yield, and accumulation of endogenous reserves, conidial attributes and virulence. Addition of KCl to SDA media (SDAM) significantly reduced germination of the three isolates in vitro and lowered germination and appressorial development on the cuticles of potato-peach aphids and pollen beetles. Conidia grown on SDAM and minimal medium (MM) were more aggressive than conidia derived from SDA or Yeast Extract Agar (YEA). Results also identified that culture media influenced virulence of M. anisopliae isolates by influencing the fungal physiological qualities such as presence or absence of erythritol and arabitol, and the balance of carbon and nitrogen (C:N ratio) in conidia. Dark, pigmented conidia from aphid...
Three newly isolated and two existing isolates of M. anisopliae and B. bassiana were tested again... more Three newly isolated and two existing isolates of M. anisopliae and B. bassiana were tested against aphids, whiteflies and beneficials, individually and with chitin synthesis inhibitor. Hundred percent of aphids have died of fungal treatments 7 days post inoculation, but number of individuals that developed mycosis varied depending on the isolate used. Whiteflies, however, were slightly more resistant. All tested isolates appeared to be fast killing fungi requiring only one or two days for reducing aphid population by half and needing 4 to 6 days for 50% of whiteflies to succumb to the disease. Both, aphid and whitefly, mortalities increased with increasing dose. The estimated LC50 values against M. persicae were 10 3.88 and 10 4.75 conidia ml -1 , respectively. These results were comparable with values obtained for the same isolates tested against whitefly Bemisia tabaci. Hundred precent of parasitized aphids by whitefly parasitoid demonstrated the emergence hole in the controls and in the individuals treated with new M. anisopliae isolate and 87% of emergence holes in the individuals treated with new B. bassiana. Exposure of mealybug predator to new isolates resulted in high mortalities. Native B. bassiana isolate in combination with diflubenzuron significantly reduced population of 1 st instar larvae of whiteflies under greenhouse conditions 14 days post treatment.
This survey was conducted in Akkar and Bekaa area (Lebanon) to determine the presence and distrib... more This survey was conducted in Akkar and Bekaa area (Lebanon) to determine the presence and distribution of the potato cyst nematode, Globodera spp. A total of 294 soil samples were collected from 32 different regions. The nematode counting in the soil samples from Akkar area revealed that 66 out of 217 samples (30.4%) contained cyst nematodes and 18 (8.3%) of the samples contained eggs. On the other hand, 77 soil samples collected from Bekaa contained cyst nematodes, 69 (89.6%) of which contained eggs. The level of infestation of nematodes was varying from one area to another. The highest level was detected in Akkar area from Klayaat with 2 eggs/1g soil and Tell Abass El Charqi with 1.7 eggs/1g soil, however, the lowest level of infection was detected in soil samples from Tell Biri (0.25 eggs/1g soil) and Abde (0.3 eggs/1g soil). The highest infection in Bekaa area was found in Khiara (5.4 eggs/1g soil) and Riak (5 eggs/1g soil). Eight different treatments using chopped plants were t...
Mycological Research, 1995
Aphids and flea beetles were differentially susceptible to the same isolates of the entomopathoge... more Aphids and flea beetles were differentially susceptible to the same isolates of the entomopathogenic Metarhizium anisopliae. Differences in susceptibility reflected the response of the pathogen to cuticular cues. More conidia adhered and germinated readily on the surfaces of live aphids and at sites under the elytra of live beetles. On dorsal elytra and the ventral thorax of live beetles poor adhesion and germination was attributed to fungistasis because no such behaviour was noted on dead beetles. The cuticle also influenced appressorium morphology and the mode of pathogeneSiS. Fewer, smaller appressoria were produced on aphid as opposed to beetle cuticle. Metarhizium anisopliae also penetrated the cuticle directly, i.e. without producing appressoria. Sites under the elytra of live flea beetles were more vulnerable to infection than sites on the dorsal elytra or ventral thorax resulting in higher mortalities and lower LT50 values.
Journal of Agricultural Science and Technology A
Fruit extracts of indigenous Melia azedarach were tested for their insecticidal bioactivity again... more Fruit extracts of indigenous Melia azedarach were tested for their insecticidal bioactivity against the tomato leafminer (Tuta absoluta) under laboratory conditions. Tomato plants were exposed to moths, after/before application of treatments. Treatments included: crushed fruit extracts of water (500,000 ppm and 200,000 ppm), methanol and ethyl acetate (200,000 ppm) with and without mineral oil (2%); M. azedarach powder extracts (2,000 ppm) in different solvents: water, methanol, ethanol, ethyl acetate, hexane and chloroform; biorational products: neem oil, mineral oil, micronized sulfur and thyme oil. The released moths were removed from treated/untreated plants at 72 h and effect of treatments on adults, eggs, larvae and pupae were recorded. Results indicated that sulfur caused the lowest number of live moths to be present on treated plants and was not significantly different in its effect from that of M. azedarach extracts and neem oil. Aqueous extracts without and with oil caused the highest % of dry eggs and were comparable to neem oil. Extracts in the two formulations (crushed fruits and/or powder) caused significant direct effects on immature instars: eggs, early larval instars and pupae. M. azedarach extracts and the tested products also caused indirect effect in form of significant decrease in number of developing the 3rd larval instars and new emerging moths compared to the control. Consecutive sprays of these extracts against eggs, larvae and pupae on same treated plants lead to very low number of moths for a second generation of the pest which contributes to low buildup of pest population in a tomato crop.
Annals of Botany
Following impact, wound healing was investigated in roots of sugar beet using¯uorescence microsco... more Following impact, wound healing was investigated in roots of sugar beet using¯uorescence microscopy in conjunction with a conventional lignin test. Samples of sugar beet roots were harvested at dierent stages of development and impacted in the laboratory with a falling bolt delivering 1±4 Joules. A response in the form of deposition of brown material, presumed to be melanin, along the outer and inner walls of cells at the wound surface was observed within 3 d of impact. This material eventually became granular in appearance. Formation of a ligno-suberized boundary layer from cells present at the time of impact ®rst occurred in 16-week-old roots 9 d after impact. Intensity of calco¯uor uorescence supported the ®ndings made using light microscopy. As wound healing progressed with time, the intensity of calco¯uor¯uorescence declined, demonstrating interference by wound healing products with calco¯uor binding. Aggressive harvest and subsequent storage dramatically reduced calco¯uor¯uorescence indicating that this dye may have potential value in the assessment of tissue damage.
Plant-parasitic nematodes on stone fruits and citrus in Lebanon
Lebanese Science Journal, 2016
Mycological Research, Jun 1, 2002
Culture media influenced the germination of conidia, appressorial development and mycelial growth... more Culture media influenced the germination of conidia, appressorial development and mycelial growth of Metarhizium anisopliae. Although the addition of KCl to Sabouraud dextrose agar (SDAM) significantly reduced germination of the conidia of three isolates in vitro and lowered germination and appressorial development on the cuticles of Myzus persicae and Meligethes aeneus, conidia grown on SDAM and minimal medium (MM) were more aggressive than conidia derived from SDA or yeast extract agar. No relationship was found between either germination or appressorial development and LT &! values, suggesting that virulence depends on the speed of infection. Calcofluor staining and lectin binding showed that culture conditions also influenced the adhesion of Metarhizium anisopliae to insect cuticles through alteration of surface carbohydrates such as 1-4-β-glucans. Dark, pigmented conidia from MM bound less lectins and calcofluor whereas the paler conidia from the other media fluoresced more intensely. Conidia from SDAM fluoresced 20-fold brighter and adhered more readily to insect cuticle compared with conidia derived from MM. Although inocula from both media showed elevated pathogenic activity against aphid and pollen beetle, MM-grown conidia were more aggressive since high mortality was induced by comparatively fewer conidia. When fluorescent intensity of calcofluor-stained conidia was compared to the number of conidia adhering to the insect cuticles, the relationship was significant, indicating that this dye has practical implications for the assessment of fungal strains in screening programmes for commercial development.
Pathogenicity of the entomogenous fungi Metarhizium anisopliae and Beauveria bassiana against crucifer pests and the honey bee
Http Dx Doi Org 10 1080 09583159409355328, Sep 17, 2008
ABSTRACT The susceptibility of the cabbage stem flea beetle (Psylliodes chrysocephala; Coleoptera... more ABSTRACT The susceptibility of the cabbage stem flea beetle (Psylliodes chrysocephala; Coleoptera: Chrysomelidae) to different isolates of the entomogenous, hyphomycete fungi Beauveria bassiana and Metarhizium anisopliae, all from heterologous hosts, was investigated. The most pathogenic isolates were of M. anisopliae (V208, V233, V234, V242, V245, and V248). Studies were conducted to determine the virulence of V208 and V245, and their specificity for three other crucifer pests, Phaedon cochleariae, Myzus persicae and Lipaphis erysimi and a beneficial insect, Apis mellifera. Flea beetle mortality rates increased with dose; the estimated LC50 S of V208 and V245 at 14 days post‐inoculation were c. 106 conidia ml‐1. The respective estimated LT50 values of V208 and V245 for P. chrysocephala at 1 × 107 conidia ml‐1 were 10.0 and 9.3 days, and at 1 × 1010 conidia ml LT50s were 3.8 and 4.2 days. Both V208 and V245 were pathogenic for P. cochleariaeM. persicae and L. erysimi. Myzus persicae and L. erysimi died within 4 days of inoculation. Bees were less susceptible to infection at low doses, but at 1 × 1010 conidia ml‐1almost all bees had died by day 5 when the estimated LT50s for V208 and V245 were 4.4 and 8.5 days respectively.
Mycological Research, Jul 1, 1999
Conidia of Metarhizium anisopliae need water activity (A w) 0n98 for germination irrespective of ... more Conidia of Metarhizium anisopliae need water activity (A w) 0n98 for germination irrespective of whether they are formulated in an aqueous or oil carrier. The presence of nutrients in the carriers or culture medium accelerated germination but did not increase the range of A w (or humidities) over which conidia could germinate. Insect extract stimulated more conidia to germinate than yeast extract. Oils appeared to extract fungistatic and stimulatory compounds from the insect cuticle. The ratio of these compounds depends on both the insect species and the carrier. Conidia of M. anisopliae formulated in oils were observed with SEM to flow over the surface of insect and plant cuticles. The conidia were probably deposited at sites which are conducive for germination and infection and consequently increased the overall mortality of insects. In contrast, aqueous formulations of conidia remain as drops on the leaf surface immediately after application with a pipetteman or sprayer.
Mass Production, Yield, Quality, Formulation and Efficacy of Entomopathogenic Metarhizium anisopliae Conidia
British Journal of Applied Science & Technology, 2015
Aims: The aim of this study was to develop an easy but robust method for mass production, to form... more Aims: The aim of this study was to develop an easy but robust method for mass production, to formulate and compare the efficacy of mass produced conidia of a local isolate Metarhizium anisopliae against aphids and oil-formulated conidia against whiteflies. Study Design: The randomized complete block design with replications. Place and Duration of Study: 2012-2014, Laboratory of Crop Protection Department, Faculty of Agricultural Engineering and Veterinary Medicine, Lebanese University. Methodology: Isolate of fungal entomopathogen M. anisopliae (Metschn.) Sorokin (LIM1) was grown on cooked rice, wheat, vegetable peels and burgul in roasting bags to produce and harvest spore powder. The cultures were dried and total yield of harvested conidia was determined. After harvesting, spores were submitted to quality control to assess concentration, germination, purity, moisture content and pathogenicity against rose aphid, Macrosiphum rosae L., mealy plum aphid, Hyalopterus pruni and melon aphid, Aphis gossypii Glover. Formulated in different oils, conidia were stored at different temperatures for 16 weeks. Oil-formulated conidia were tested against whiteflies under field conditions. Results: Among the substrates studied, burgul had the highest yield (21 g/100 g substrate). The optimum time for harvesting was 3 weeks. C:N ratio was also the lowest for conidia produced on burgul which caused the highest mortalities and thus appeared the most virulent against all tested insects. Sunflower oil formulated conidia retained viability for at least 16 weeks at room temperature. The preliminary results indicated some but not significant control of whiteflies in the pot experiments. Conclusion: M. anisopliae could be mass produced in large quantities on burgul substrate. The quality of produced inocula as measured by endogenous C:N ratios would be largely affected by substrate used for mass production. The quality would also influence the efficacy against target insects. Mass produced conidia could also be stored as dry or formulated in sunflower oil at room temperature up to 16 weeks. Use of endogenous C:N ratio as quality control indicator for high quality inocula is highly recommended. Use of vegetable peels as potential substrate for mass production combined with a recyclable oil as formulant could be a low cost and environmentally sustainable technology for future mass production of entomogenous fungi.
Chemical composition and antimicrobial activities of essential oil and its components from LebaneseOriganum syriacumL
Journal of Essential Oil Research, 2012
International Journal of Botany, 2011
Mycological Research, 2002
Culture media influenced the germination of conidia, appressorial development and mycelial growth... more Culture media influenced the germination of conidia, appressorial development and mycelial growth of Metarhizium anisopliae. Although the addition of KCl to Sabouraud dextrose agar (SDAM) significantly reduced germination of the conidia of three isolates in vitro and lowered germination and appressorial development on the cuticles of Myzus persicae and Meligethes aeneus, conidia grown on SDAM and minimal medium (MM) were more aggressive than conidia derived from SDA or yeast extract agar. No relationship was found between either germination or appressorial development and LT &! values, suggesting that virulence depends on the speed of infection. Calcofluor staining and lectin binding showed that culture conditions also influenced the adhesion of Metarhizium anisopliae to insect cuticles through alteration of surface carbohydrates such as 1-4-β-glucans. Dark, pigmented conidia from MM bound less lectins and calcofluor whereas the paler conidia from the other media fluoresced more intensely. Conidia from SDAM fluoresced 20-fold brighter and adhered more readily to insect cuticle compared with conidia derived from MM. Although inocula from both media showed elevated pathogenic activity against aphid and pollen beetle, MM-grown conidia were more aggressive since high mortality was induced by comparatively fewer conidia. When fluorescent intensity of calcofluor-stained conidia was compared to the number of conidia adhering to the insect cuticles, the relationship was significant, indicating that this dye has practical implications for the assessment of fungal strains in screening programmes for commercial development.
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Papers by Ludmilla Ibrahim