Antibacterial activity of guava, moringa, camphor bush and pelargonium extracts against bacterial wilt (Ralstonia pseudosolanacearum sp. nov.) of potato.

Bacterial wilt (Ralstonia pseudosolanacearum sp. nov.) is a major disease devastating global potato production. Proposed management options are mostly expensive and ineffective. This has necessitated efforts to develop cheaper and eco-friendly management options such as use of botanicals. Antibacterial activity of ethanol and acetone plant extracts from guava (Psidium guajava), drumstick (Moringa oleifera), camphor bush (Tarchonanthus camphoratus) and pelargonium (Pelargonium zonale) against R. pseudosolanacearum sp. nov. was evaluated in-vitro at a concentration of 100 mg/mL of 1 % Dimethlysulfoxide (DMSO) using disk diffusion technique. The R. pseudosolanacearum sp. nov was isolated from infected haulms collected from potato growing field at the University of Nairobi. The most effective extracts were subjected to further screening at different concentrations to determine their minimum inhibitory concentrations (MICs). All the four plant extracts showed varied antibacterial efficacy. P. zonale leaves extract was the most effective with growth inhibition zone of 18.73 mm and 18.60 mm for ethanol and acetone solvents respectively. The average of growth inhibition zones for each plant extract was not significantly different at p ≤ 0.05 among extraction solvents. The minimum inhibitory concentration (MIC) results showed that antibacterial activity of P. zonale and P. guajava leaf started at 6.25 mg/mL with growth inhibition zones of 7.67 and 8.0 mm for ethanol and acetone solvents respectively. P. zonale and P. guajava leaf extracts exhibited significantly higher antibacterial activity at p ≤ 0.05 compared to other extracts. Thus, further research should be conducted to assess their antibacterial potency against R. pseudosolanacearum sp. nov. both in-vivo and under field condition.

Biological and biorational management of blast diseases in cereals caused by Magnaporthe oryzae.

Blast diseases, caused by the fungal pathogen Magnaporthe oryzae, are among the most destructive diseases that occur on at least 50 species of grasses, including cultivated cereals wheat, and rice. Although fungicidal control of blast diseases has widely been researched, development of resistance of the pathogen against commercially available products makes this approach unreliable. Novel approaches such as the application of biopesticides against the blast fungus are needed for sustainable management of this economically important disease. Antagonistic microorganisms, such as fungi and probiotic bacteria from diverse taxonomic genera were found to suppress blast fungi both in vitro and in vivo. Various classes of secondary metabolites, such as alkaloids, phenolics, and terpenoids of plant and microbial origin significantly inhibit fungal growth and may also be effective in managing blast diseases. Common modes of action of microbial biocontrol agents include: antibiosis, production of lytic enzymes, induction of systemic resistance in host plant, and competition for nutrients or space. However, the precise mechanism of biocontrol of the blast fungus by antagonistic microorganisms and/or their bioactive secondary metabolites is not well understood. Commercial formulations of biocontrol agents and bioactive natural products could be cost-effective and sustainable but their availability at this time is extremely limited. This review updates our knowledge on the infection pathway of the wheat blast fungus, catalogs naturally occurring biocontrol agents that may be effective against blast diseases, and discusses their role in sustainable management of the disease.

Co-culture development and bioformulation efficacy of psychrotrophic PGPRs to promote growth and development of Pea (Pisum sativum) plant.

Numerous microbes reside in the rhizosphere having plant growth promoting activity, and enhancing the property by increasing plant yield. Plant growth promoting rhizobacteria (PGPR) has gradually increased in agriculture and offers an attractive way to replace chemical fertilizers, pesticides and supplements. Soil was collected from the rhizosphere of an agricultural farm and the psychrotrophic bacterial strains STA3 (KY888133) and RM2 (KY888134) were successfully isolated, and screened on the basis of phosphate solubilization. Further characterization was carried out by morphological, biochemical, and 16S rDNA characterization methods. The unique nature of psychrotrophic Pentoea ananatis and a suitable combination with Pseudomonas fluorescens regarding plant growth promotion activity has not been studied before to our knowledge. An assessment of various parameters of plant growth promoting activity, such as IAA, phosphate solubilization, bio-control activity, HCN and siderophore production, has been carried out. Both strains were found to be positive in various parameters except HCN and Biocontrol activity, which were positive only for the strain RM2. Also, shelf life and their efficacy was determined before and after formulation. A great consistency was observed in all the cultures, even after 70 days of storage under bio-formulation at room temperature, while in the case of the co-culture CPP-2, the cfu ml-1 was greater, followed by RM2 and STA3. Moreover, the growth indices of the pea plant were found to be better in the co-culture CPP-2 compared with individual strains, followed by RM2 and STA3. Thus, the study suggests that the co-culture CPP-2 has a great potential for plant growth promotion as compared with individual strains followed by RM2 and STA3.

Essential oils from Algerian species of Mentha as new bio-control agents against phytopathogen strains.

Chemical composition and antifungal activity of essential oils of Algerian Mentha species were studied. Chemical compositions of different Mentha species oils (Mentha rotundifolia, M. spicata, M. pulegium, and M. piperita) were investigated by capillary GC and GC/MS, and their antifungal activities were evaluated by means of paper disc diffusion method and minimum inhibitory concentration (MIC) assays. In total, 98 components from all Mentha species were identified. All oils were rich in monoterpene-oxygenated components. In addition, we reported fumigant antifungal activity of Algerian Mentha essential oils against four fungi: Botrytis cinerea, Penicillium expansum, Monilinia laxa, and M. fructigena. All oils demonstrated very good inhibition especially against B. cinerea, M. laxa, and M. fructigena. Both Monilinia fungi were extremely sensitive to all Algerian Mentha oils, which suggests that Mentha essential oils have the potential to be used as bio-pesticides to protect fruit trees, such as apple and pear trees, and provides an alternative to chemical pesticides.

Management of blight of bell pepper (Capsicum annuum var. grossum) caused by Drechslera bicolor

Abstract Sweet or bell pepper is a member of the Solanaceae family and is regarded as one of the most popular and nutritious vegetable. Blight, in the form of leaf and fruit blight, has been observed to infect bell pepper crops cultivated at the horticulture farm in Rajasthan College of Agriculture, Udaipur, India. Based on disease severity, we attempted to curb this newly emerged problem using different fungicides, plant extracts, bio-control agents, and commercial botanicals against the fungus in laboratory and pot experiments. Bio-control agent Trichoderma viride and plant growth promoting Rhizobacteria (PGPR) isolate Neist-2 were found to be quite effective against bell pepper blight. All evaluated fungicides, botanicals, commercial botanicals, and bio-control agents in vitro were further studied as seed dressers and two foliar sprays at ten days interval in pot experiments. The combinations of Vitavax, PGPR isolate Neist-2, and Mehandi extract were found to be very effective against bell pepper blight followed by Vitavax, T. viride, and Mehandi extract used individually. All treatments in the pot experiments were found to significantly reduce seedling mortality and enhance plant biomass of bell pepper. Thus, these experimental findings suggest that a better integrated management of bell pepper blight could be achieved by conducting field trials in major bell pepper- and chilli-cultivated areas of the state. Besides fungicides, different botanicals and commercial botanicals also seem to be promising treatment options. Therefore, the outcome of the present study provides an alternate option of fungicide use in minimizing loss caused by Drechslera bicolor.

Management of blight of bell pepper (Capsicum annuum var. grossum) caused by Drechslera bicolor.

Sweet or bell pepper is a member of the Solanaceae family and is regarded as one of the most popular and nutritious vegetable. Blight, in the form of leaf and fruit blight, has been observed to infect bell pepper crops cultivated at the horticulture farm in Rajasthan College of Agriculture, Udaipur, India. Based on disease severity, we attempted to curb this newly emerged problem using different fungicides, plant extracts, bio-control agents, and commercial botanicals against the fungus in laboratory and pot experiments. Bio-control agent Trichoderma viride and plant growth promoting Rhizobacteria (PGPR) isolate Neist-2 were found to be quite effective against bell pepper blight. All evaluated fungicides, botanicals, commercial botanicals, and bio-control agents in vitro were further studied as seed dressers and two foliar sprays at ten days interval in pot experiments. The combinations of Vitavax, PGPR isolate Neist-2, and Mehandi extract were found to be very effective against bell pepper blight followed by Vitavax, T. viride, and Mehandi extract used individually. All treatments in the pot experiments were found to significantly reduce seedling mortality and enhance plant biomass of bell pepper. Thus, these experimental findings suggest that a better integrated management of bell pepper blight could be achieved by conducting field trials in major bell pepper- and chilli-cultivated areas of the state. Besides fungicides, different botanicals and commercial botanicals also seem to be promising treatment options. Therefore, the outcome of the present study provides an alternate option of fungicide use in minimizing loss caused by Drechslera bicolor.

Potential Bio-Control Agent from Rhodomyrtus tomentosa against Listeria monocytogenes.

Listeria monocytogenes is an important foodborne pathogen implicated in many outbreaks of listeriosis. This study aimed at screening for the potential use of Rhodomyrtus tomentosa ethanolic leaf extract as a bio-control agent against L. monocytogenes. Twenty-two L. monocytogenes isolates were checked with 16 commercial antibiotics and isolates displayed resistance to 10 antibiotics. All the tested isolates were sensitive to the extract with inhibition zones ranging from 14 to 16 mm. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values ranged from 16 to 32 µg/mL and 128 to 512 µg/mL, respectively. Time-kill assay showed that the extract had remarkable bactericidal effects on L. monocytogenes. The extract at a concentration of 16 µg/mL reduced tolerance to 10% NaCl in L. monocytogenes in 4 h. Stationary phase L. monocytogenes cells were rapidly inactivated by greater than 3-log units within 30 min of contact time with R. tomentosa extract at 128 µg/mL. Electron microscopy revealed fragmentary bacteria with changes in the physical and morphological properties. Our study demonstrates the potential of the extract for further development into a bio-control agent in food to prevent the incidence of L. monocytogenes contamination.

Lethal response of the dengue vectors to the plant extracts from family Anacardiaceae

Objective: To explore the larvicidal activities of different plant parts of Melanochyla fasciculiflora (. M. fasciculiflora), Gluta renghas (. G. renghas), Anacardium occidentale and Mangifera indica from family Anacardiaceae against the laboratory and field strains of dengue vectors Aedes aegypti and Aedes albopictus (. Ae. albopictus). Methods: Leaves and bark parts of study plants were collected from Taman Nageri, Bukit Pancor and Teluk Bahang National Park, Penang, Malaysia. Leaves and stem barks were separated, air dried, ground and extracted with methanol by Soxhlet apparatus. Crude extract was obtained by evaporating the extra solvent in rotary evaporator. The 4th instar larvae from laboratory and field strains were exposed to 50-1. 300 mg/L concentrations according to World Health Organization standard larval bioassay. Larval mortality was recorded after 24 h of exposure. Results: Highest larvicidal activity was exhibited by G. renghas bark extract against Ae. albopictus laboratory strain at 600 mg/L. G. renghas also showed the highest larvicidal activities for other strains as compared to other plant extracts, followed by Mangifera indica and M. fasciculiflora and Anacardium occidentale. Conclusions: Ae. albopictus has been found to be more susceptible as compare to Aedes aegypti in both laboratory and field strains in this study. G. renghas and M. fasciculiflora were tested for the first time and exhibited prompting larvicidal activities against dengue vectors. These results revealed that all the plants especially G. renghas and M. fasciculiflora have the higher larvicidal activities and can be used for the control of dengue vector as a new environment friendly, target specific and low cost phytochemical.

Lethal response of the dengue vectors to the plant extracts from family Anacardiaceae

Objective:To explore the larvicidal activities of different plant parts ofMelanochyla fasciculiflora(M. fasciculiflora),Gluta renghas(G. renghas),Anacardium occidentale and Mangifera indica from family Anacardiaceae against the laboratory and field strains of dengue vectorsAedes aegyptiandAedes albopictus(Ae. albopictus). Methods: Leaves and bark parts of study plants were collected from Taman Nageri, Bukit Pancor and Teluk Bahang National Park, Penang, Malaysia. Leaves and stem barks were separated, air dried, ground and extracted with methanol by Soxhlet apparatus. Crude extract was obtained by evaporating the extra solvent in rotary evaporator. The 4th instar larvae from laboratory and field strains were exposed to 50-1 300 mg/L concentrations according to World Health Organization standard larval bioassay. Larval mortality was recorded after 24 h of exposure. Results: Highest larvicidal activity was exhibited byG. renghas bark extract againstAe. albopictus laboratory strain at 600 mg/L.G. renghas also showed the highest larvicidal activities for other strains as compared to other plant extracts, followed byMangifera indica andM. fasciculilfora andAnacardium occidentale. Conclusions:Ae.albopictus has been found to be more susceptible as compare toAedes aegypti in both laboratory and field strains in this study.G. renghas andM. fasciculiflora were tested for the first time and exhibited prompting larvicidal activities against dengue vectors. These results revealed that all the plants especiallyG. renghas andM. fasciculilfora have the higher larvicidal activities and can be used for the control of dengue vector as a new environment friendly, target specific and low cost phytochemical.

Phytotherapeutic activity of Euphorbia cyparissias extracts on Ixodidae (Acari) female ticks.

BACKGROUND: Given its numerous biologically active components, Euphorbiaceae has been found to be a large plant family and polyvalent with quite interesting therapeutic activity that can be studied. MATERIALS AND METHODS: The ixodicidal activity of Euphorbia cyparissias extracts was studied in vitro and in vivo. Tested concentrations were 10, 5, 2, 1, 0.5 and 0.25%. RESULTS: For the in vitro study, conducted on field-collected female specimens of Dermacentor marginatus and Haemaphysalis punctata, the efficacy results showed that the ticks died after exposure in the case of 10, 5, and 2% tincture concentrations. The effects appeared after 30 minutes and became more visible 120 minutes after each exposure. The statistical differences regarding the used concentrations were found to be: F = 6.51, df = 5, P < 0.001. The in vivo study of the efficacy of E. cyparissias concentrations was performed on 35 naturally infested sheep and on 30 bovines parasitized with Ixodes ricinus, sprayed with tincture and glycerinate dilutions (bovines) on days 0 and 7. The results revealed detrimental effects on the survivability of female ticks, the most prominent being the reduction of their movement capacity. In sheep in vivo efficiency observed within 24 hrs varied, between 1 and 23% for D. marginatus and between 7 and 27% for H. punctata and respectively between 2 and 53% after 24 hrs, for I. ricinus, comparable effects being also found 72 hrs after the second administration of Euphorbia extracts. CONCLUSION: Extracts from E. cyparissias may be used, with results, as an ecologic alternative tick control management method, being a cheap solution, with a sizeable role in reducing the use of synthetic and/or other harming and resistance source ixodicidal conditionings.