Biocontrol

Isolation and biochemical characterization of Plant Growth Promoting (PGP) bacteria colonizing the rhizosphere of Tef crop during the seedling stage

Published on: 28th March, 2019

OCLC Number/Unique Identifier: 8056258929

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.
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Non-chemical control of Armillaria mellea infection of Prunus persica

Published on: 4th July, 2019

OCLC Number/Unique Identifier: 8186251364

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.
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Nematicidal effect of abamectin, boron, chitosan, hydrogen peroxide and Bacillus thuringiensis against citrus nematode on Valencia orang

Published on: 12th December, 2019

OCLC Number/Unique Identifier: 8495684933

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.
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Potential of Pleurotus sajor-caju compost for controlling Meloidogyne incognita and improve nutritional status of tomato plants

Published on: 30th December, 2019

OCLC Number/Unique Identifier: 8507798528

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.
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