biocontrol

The use of novel PGPR as bio inoculant is an alternative sustainable agricultural practice to improve soil health, grain quality, increase crop productivity, and conserve biodiversity. The aim of this study is to isolate, and characterized PGP bacteria colonizing tef rhizosphere during the seedling stage. For this concern, 426 samples of tef (Eragrostis tef) rhizosphere soils and roots were collected from East Shewa zone, Oromia regional state. 200 morphologically different bacterial pure colonies were isolated and screened for their PGP traits and biocontrol properties. Among these 40.5% isolates were positive for phosphate solubilization. 36% were positive for IAA production, 4.5% were positive for ammonia production, 19 % were positive for (EXPS), 15.5% were positive for protease production, 12.5% were positive for HCN productions, 9.5 % were positive for cellulase production, 4% were positive for amylase production, 3.5% were positive for chitinase production. For abiotic stress tolerance test, all of the isolates were grown well at 20oc and 30oc and neutral pH, 27% isolates were grown well at 4oc, 25.5% grew at 40oc, 25.5% were grown well on pH-9 and pH-11, 23.5% were tolerated pH-5, 3.5% grew at 50oc and 60oc, 13.5% were grown well on 5% NaCl (w/v), 3.5% were grown well on 10 and 15% NaCl (w/v), which indicated these isolates can survive in some extreme conditions. Totally 15 bacterial species having PGP traits, biocontrol properties, and abiotic stress tolerance ability were identified using the Biolog bacterial identification system. Among these, the majority of the identified PGPR have utilized carbohydrate, carboxylic acid, and amino acid, which are the main components of plant root exudates. The above results indicated that thus PGPR can be used as biofertilizers as well as biocontrol agents to replace agrochemicals to improve crop productivity. Hence, these species can be further formulated and used for greenhouse and field applications.

Peaches, Prunus persica were planted as grafted saplings in an avocado orchard previously infested with Armillaria mellea (Vahl) P.Kumm. Trees were planted in large or small holes with or without fresh yardwaste chips added as an amendment and with or without a Trichoderma biocontrol product sprayed into the hole. Trees were monitored for six years -- growth and mortality was tabulated. Six years later 40% of the trees had died from the disease. Trees planted in a large hole were more likely to survive than in a smaller hole (P=0.07) and trees in large holes with fresh organic matter added were the most likely to survive (P=0.04). Trichoderma sprays in the planting hole did not increase survival rates. While growth was initially retarded by adding fresh yardwaste to the hole, in later years none of the treatments affected growth rates.

The nematicidal efficacy of abamectin, boron, chitosan, hydrogen peroxide, Bacillus thuringiensis and oxamyl 24% SL against citrus nematode, Tylenchulus semipenetrans were examined on Valencia orange trees under field condition for two successive seasons (2017 and 2018). The experiment was conducted in a Valencia orange orchard infested with citrus nematode at Nubaria, El-Behera governorate, Egypt. The obtained results showed that all the tested treatments reduced nematode final population ((Pf) and reproduction factor (Rf) compared with that obtained from the untreated trees. The highest percentages of Pf reductions (74.5-83.4 %) and (70%-82%) were recorded with oxamyl, boron, abamectin, chitosan and H2O2 in the 1st and the 2nd tested seasons, respectively. Whereas, B. thuringiensis had the least nematode Pf reduction with 60.7 and 55.8% in the 1st and 2nd seasons, respectively. Additionally, all treatments significantly improved orange yield (30.9-83.2% increase), physical fruit parameters and orange juice properties. The highest orange yield increase (83.2%) was recorded with boron treatment followed by oxamyl (70.3%). Also, boron increased total soluble solids (TSS) by 13.6%, volume of orange juice (36.4%) and vitamin C (19.7%) and decreased juice acidity (A) by (16.7%). It is concluded that abamectin, boron and the other tested compounds have potential as non-chemical control strategy tools in managing the citrus nematode. These bioagents reduced the amount of traditional chemical nematicides and are considered to be environmentally safe.

The potential of spent compost of oyster mushroom, Pleurotus sajor-caju cultivated on rice (MCR) or wheat straws (MCW) was evaluated against the root-knot nematode, Meloidogyne incognita on tomato plants under field conditions during two successive seasons (2016 and 2017). The field trial was carried out in a clay loam soil naturally infested with M. incognita at a private farm, Kafr El-Sheikh governorate, Egypt. Results revealed that all the tested treatments greatly suppressed final populations (Pf), numbers of galls and egg masses of M. incognita during both seasons as compared to the untreated treatment. The highest percentages of Pf reductions (81.1 - 87%) and (80.2 - 86.2%) were achieved with the chemical nematicide, Vydate® 10 G and treatments of (MCR and MCW) at application rate of 1200 g/m2 in the 1st and 2nd seasons, respectively. Moreover, the fruit yield during both seasons was increased significantly with all the applied treatments, especially treatment of MCW at application rate of 1200 g/m2. Additionally, chemical fruit properties were markedly improved with MCR and MCW treatments. Also, treatments of MCR and MCW achieved the highest percentages of nitrogen and phosphorus contents. Generally, the results indicated that spent compost obtained after cultivation of P. sajor-caju has a nematicidal potential against M. incognita, also improved nutritional status and increased tomato yield.

The post-harvest health and microbial safety of plant products and foods continue to be a global concern to farmers, consumers, regulatory agencies and food industries. A study was carried out to evaluate the pathogenicity of fungi associated with post-harvest rot of oranges, watermelons and bananas in Lafia, Nasarawa State, Nigeria. Healthy fruits inoculated with fungal spores obtained from rotted fruit tissues were incubated at ambient temperature conditions and observed daily for the appearance and development of tissue rot. Oranges and Watermelons had the highest number of fungal isolates (3) compared to banana (2). Fungi belonging to the genus Curvularia were the most isolated (37.50%), followed by both Aspergillus and Colletotrichum (25.00% respectively) and lastly Alternaria (12.50%). The highest tissue rot diameter of sweet orange (2.40 cm) was induced by Alternaria sp. followed by Curvularia geniculate (1.40 cm) and lastly Colletotrichum sp. (1.28 cm). The highest rot of banana fruit tissues was produced by A. niger (3.90 cm), followed by Curvularia geniculate (3.40 cm). Aspergillus sp. produced the highest tissue rot diameter on watermelon fruits (1.93 cm), followed by Colletotrichum sp. (1.30 cm) and lastly Curvularia geniculate (1.20 cm). Differences in the susceptibilities of different fruits to rot by fungal pathogens were significant (p ≤ 0.05). There is need for improved handling of fruits after harvest to prevent losses due to bacterial and fungal rots in the study area.

Gray mold disease, caused by the fungus Botrytis cinerea, causes heavy losses in strawberries. The use of chemical fungicides due to the dangers for humans and the environment has caused attention to reduce their consumption and use biological methods. In this research, the effects of zinc oxide, copper, and silver nanoparticles have been synthesized from an aqueous extract of cloves, and the probiotic bacteria Lactobacillus casei by the green method was investigated on the gray mold disease of strawberries. The results showed that concentrations of 10% of zinc oxide nanoparticles synthesized from aqueous extract of cloves can completely control this pathogen on the culture medium and the fruit. Zinc and silver nanoparticles produced by Lactobacillus casei prevented 93.7% and 81% of fungal growth in the culture medium, respectively. Other treatments did not show a good inhibitory effect on the fungus. All treatments were able to prevent 100% to 50% of fungal growth after 96 hours on strawberries. The investigation of the storage characteristics showed the positive effect of the examined nanoparticles on reducing the rate of change of the physicochemical characteristics of the strawberry fruit tissue. Apparent decay was significantly reduced and samples treated with nanoparticles scored higher in sensory evaluation compared to control. Also, investigating the toxicity of nanoparticles in this experiment on the HepG2 cell line showed that Compared to the control, copper and zinc nanoparticles did not have significant toxicity on cells, but silver nanoparticles led to 25% cell death. This research provides promising results in the field of using nanoparticles for pre-harvest and post-harvest control of plant diseases.