No abstract

Biological control using rhizosphere bacteria, Pseudomonas spp. and Serratia spp. is a prospective alternative technique to overcome plant parasitic nematodes infection. So, the current study was conducted in vitro on five egg-masses, 100 free eggs and 100 infective juveniles (IJs) of Meloidogyne incognita as well as greenhouse treatments on Luffa aegyptiaca L. to evaluate the nematicidal potential of six strains belong to Pseudomonas spp. and Serratia spp. as compared to oxamyl. Results showed that the inhibitory effect and juvenile mortality varied according to bacteria species, strains and exposure time. All the tested bacteria significantly ( P ≤ 0.05) inhibited egg hatching and increased juvenile mortality in vitro . After 3 days of treatment, Pseudomonas spp. were more effective against eggs (48.31to 55.15%) and IJs (20.98 to 25.30%) than Serratia spp. (44.55 to 49.75% with eggs) and (19.06 to 21.61% with IJs), respectively. In the pot experiment, Luffa aegyptiaca L. treated with Serratia spp. and Pseudomonas spp. displayed significantly higher ( P ≤ 0.05) levels of growth (as indicated by root length, fresh roots weight and fresh shoots weight) compared to control plants and significantly ( P ≤ 0.05) suppressed galling (number of galls) and reproduction (as indicated by number of egg-masses on roots and number of eggs and juveniles in pot soil). Meanwhile, among the treated plants, Serratia spp. and Pseudomonas spp. gave the best results in shoot weight of pots infected by eggs of M. incognita than those infected with IJs as compared with positive control. While, oxamyl treatment gave the best results in pots infected by eggs and IJs. The lowest galling (gall index), number of eggs and juveniles in soil was observed in the treatment with mixture of Serratia spp. and Pseudomonas spp. as well as, enhanced growth of sponge gourd more than application each of them alone. Pots treated with oxamyl overwhelmed those treated with mixture of Serratia spp. and Pseudomonas spp.

Background Acceptable alternative eco-friendly tools in the present study were tested to control the root-knot nematode, Meloidogyne incognita, on greenhouse-cultivated vegetables. The nematicidal effect of rhizobacteria (Pseudomonas and Serratia), egg parasitic fungus (Purpureocillium lilacinum), abamectin (Streptomyces avermitilis), and 3 botanicals (colocynth, Citrullus colocynthis; moringa, Moringa oleifera; marigold, Tagetes erecta L.) singly or in combination was tested against M. incognita, in comparison with emamectin benzoate. Results In vitro treatments revealed that egg hatching and juvenile mortality were influenced by the type of bioagents, plant species of botanicals, and exposure time. All the tested bioagents and botanicals displayed nematicidal potential via their ovicidal and larvicidal action on egg hatching and J2 mortality of M. incognita. Three and 5 days post-treatment, abamectin and emamectin benzoate were more effective than P. lilacinum, Serratia and Pseudomonas, and C. colocynthis in inhibiting egg hatching: 96.31 and 94.88%; 95.79 and 94.05%; 94.11 and 94.46%; 85.54 and 87.28%; 88.87 and 84.30%, respectively. On the other hand, after 10 days, P. lilacinum gave the highest inhibition percentage (99.00%), followed by abamectin (89.25%). However, the difference was insignificant compared with the inhibition percentage of rhizobacteria, Serratia and Pseudomonas (88.69%; p ≤ 0.05). Moreover, juvenile mortality was 100.0, 96.80, and 91.60% after 10 days of treatment, respectively. However, botanicals showed a lower effect on egg hatching and juvenile mortality. Under greenhouse conditions, potential antagonism towards M. incognita by application the mixture of biocontrol agents and botanicals was more effective in controlling M. incognita than single treatments. Conclusions The combination of abamectin and/or emamectin benzoate with P. lilacinum and rhizobacteria was the most effective against M. incognita, followed by rhizobacteria and P. lilacinum, not only in decreasing galls and reproduction of M. incognita but also in increasing plant growth of tomato parameters than the control. The application of various bioagents including abamectin might be a potential antagonism strategy against phytonematodes in protected agricultural areas.

A greenhouse experiment was carried out to evaluate the nematicidal activity of animal manures viz. chicken and goat manures, biopesticides viz. bio-zeid and nemex against Meloidogyne incognita infecting three cucurbits compared with oxamyl. Cucurbit plants namely cucumber (Cucumis sativus L.) cv. Biet Alpha, squash (Cucurbita pepo L.) cv. Escandrany and watermelon (Citrullus lanatus) cvs. Master and. Mloky were chosen for this study. Results indicated that of five tested materials, oxamyl, chicken and goat manures were the most effective in suppressing root galling and number of egg masses of M.incognita infecting cucurbit plants. Oxamyl (69.22%), chicken (60.98%) and goat (56.60 %) manures showed better performance in reducing root galling on cucumber than did on squash. Among the two cultivars of watermelon, the effectiveness of oxamyl (70.75), chicken (52.29) and goat (49.22%) manures were more pronounced on Master than on Mloky cultivar with root galling reached 50.74, 28.36 and 23.88% respectively. On the other hand, all treatments showed significant (P ≤ 0.05) improvement in cucurbits to certain extent. The maximum percentage of increase in shoot fresh weight was recorded on cucumber (93.30; 74.76%) and watermelon cv. Mloky (92.74; 76.81%) in pots receiving oxamyl and chicken manure, respectively. In general, number of galls showing fewer and smaller gall diameter (˂ 2 mm) was significantly decreased by oxamyl, chicken and goat manures in the three plant species. Our results showed that chicken and goat manures could be used to increase crop yield of cucurbit plants and for controlling root-knot nematode, M.incognita .

Characterizing entomopathogenic nematode (EPN) biogeography with a goal of augmentation and conservation biological control requires fine-scale taxonomic resolution, because closely related EPN species can exhibit divergent phenotypes for key properties such as habitat adaptation and insect host specificity. Consequently, we employed high throughput genome sequencing (HTS) to identify and compare EPNs and natural enemies of EPNs in 58 citrus orchards in 2 ecoregions in Egypt (El Beheira and Al Qalyubia governorates). We designed improved primers targeting the ITS2 rDNA to discriminate EPN species and used pre-reported primers targeting D2-D3 region for soil microarthropods. Five EPN species (Heterorhabditis bacteriophora, H. indica, H. taysearae, Steinernema glaseri, and S. scapterisci) and one steinernematid not represented in Genbank databases were detected. This is the first report of S. scapterisci and possibly the unknown (perhaps undescribed) species in Egypt. Only heterorhabditid species, dominated by H. indica, were detected in the reclaimed, sandy desert soils of El Beheira governorate. In the fine textured, ancient farming lands of the Nile delta all six species were detected, but at lower frequency and abundance. Microarthropod family richness (P = 0.01) and abundance (P = 0.001) was higher in the reclaimed lands than in the Nile Delta. Soil clay content, pH and elevation explained significant variation in the mite community structure. Population density of H. indica, the only EPN found consistently and at high abundance in El-Beheira, was inversely related to abundance of species in the nematophagous mite family Rhodacaridae.