Root-knot nematodes (RKNs) are one of the major constraints of vegetable cultivation worldwide. Chemical nematicides, the primary management tool for over 50 years, have a negative impact on the environment and the ineffectiveness after prolonged use. Biological control using eco-friendly rhizosphere bacteria antagonistic to nematodes is one of the alternative approaches. The objective of this study was to improve the nematicidal activity of Bacillus amyloliquefaciens subsp. plantarum SA5 and Lysinibacillus sphaericus Amira strain against RKN Meloidogyne incognita, using the protoplast technique. Their fusants were tested for their chitinase and nematicidal activity using bioassay and greenhouse experiments. The selected fusants from the two bacterial strains were more effective in killing M. incognita J 2 under laboratory conditions. Percentage mortality after 24 h of exposure were 70. 85, 84.69, 95.56, 94.99, 100, and 89.46% due to the parental strains B. amyloliquefaciens and L. sphaericus and the fusants Bas3, Bas6-2, Bas8, and Bas11, respectively. There was a positive correlation between the chitinase production and the nematicidal effect of the bacterial strains. Under greenhouse conditions, Bas8 which produced the highest amount of chitinase induced the greatest reduction in nematode counts and gave the best results in shoot length and fresh and dry weights as compared to control. Chitinase production of fusant was much higher under solid-state fermentation (SSF) than submerged fermentation conditions. The recorded chitinase produced by B. amyloliquefaciens, L. sphaericus, and Bas8 were 0, 1393, and 3399 units (μg NAG/ml enzyme/h), respectively, under solid-state fermentation and 90, 85, and 143 units (μg NAG/ml enzyme/h), respectively, under submerged fermentation conditions. Protoplast fusion was a powerful technique in improving nematicidal activity. Chitinase production is an important factor in improving the nematicidal activity of such microorganisms. The obtained improved fusant could be used as a biological control agent for M. incognita.

Background: Microbial cultures are extensively used as environment friendly ways for biological control of parasitic pests, including the root-knot nematodes, alternative to the use of chemical nematicides. The present study was conducted to isolate some lytic rhizobacteria and examine their nematicidal activity against Meloidogyne incognita J 2 mortality and egg hatching in in vitro test. Results: Lytic Rhizobacteria were isolated from soil samples adhering to tomato plant roots from different localities at Giza governorate, Egypt. Six bacterial isolates, exhibited high efficacy against root-knot nematodes, were identified based on the analysis of the 16S rRNA gene sequence as Pseudomonas aeruginosa, Paenibacillus polymyxa, Lysinibacillus sphaericus, Bacillus cereus, Bacillus subtilis, and Achromobacter xylosoxidans. These strains showed high production of chitinase, chitosanase, and protease using colloidal chitin and soluble chitosan as carbon sources. Two strains, Paenibacillus polymyxa and Bacillus subtilis, produced the highest levels of chitinase in the media. Except for Pseudomonas aeruginosa, all the bacterial strains produced high levels of chitosanase. Conclusion: The results revealed that high amounts of protease were, however, secreted by Pseudomonas aeruginosa as compared to the other strains. In in vitro tests, all the bacterial culture filtrates potentially displayed nematicidal effect in M. incognita egg hatching and an obvious increase in J 2 mortality as compared to control. Paenibacillus polymyxa caused 100% juvenile mortality followed by Bacillus subtilis 97.25%, Bacillus cereus 94%, Achromobacter xylosoxidans 93%, Lysinibacillus sphaericus 92%, and Pseudomonas aeruginosa 84.29% after 48 h of exposure, as compared to control.

Background Root-knot nematodes in general and Meloidogyne incognita, in particular, are pests that cause agricultural losses. Currently, nematode control relies on chemical nematicides, which are hazardous to the environment and human health. The increasing demand for ecofriendly nematicides has prompted researchers to look into biocontrol agents that act as efficient and long-lasting alternatives to the currently used chemicals. Objective The aim of the study was to evaluate the in-vitro nematicidal activity of eight mushroom (Cordyceps militaris, Metacordyceps neogunnii, Hericium erinaceus, Dictyophora indusiata, Cerioporus squamosus, Tirmania nivea, Tirmania pinoyi, and Agaricus impudicus) extracts against M. incognita juveniles and eggs. Materials and methods Hydromethanolic extracts were prepared from the fruiting bodies of mushrooms under investigation. Then the obtained extracts were evaluated for their in-vitro nematicidal activity against M. incognita juveniles’ second stage after 24, 48, and 72 h of treatment, also against their eggs. Results and conclusion All tested mushroom extracts were capable of inducing mortality in M. incognita second stage juveniles with mortality percentages ranging from 79.3 to 97%. On the other hand, the tested mushroom extracts exhibited some nematostatic and nematicidal activity against M. incognita eggs as compared with the control after 7 days using 80 µl/ml concentration. The tested mushroom extracts caused suppression in M. incognita eggs hatching with inhibition rates that ranged from 59.38 to 81.25%. A. impudicus hydromethanolic extract showed the highest inhibition as compared with the control and other tested mushroom extracts as it caused a relative suppression that reached 81.25% against M. incognita eggs after 7 days of exposure. The same mushroom extract has achieved a juveniles mortality of 97%. A. impudicus extract is nominated as a potential nematicidal agent. Further studies are required to confirm the potency of this extract and analyze its chemical profile.

Serratia marcescens (SM) is currently considered as a biocontrol agent against plant parasitic nematodes. It is one of the most effective bacteria for degradation of chitin. This lytic bacteria was evaluated on the survival of Meloidogyne incognita juveniles under laboratory conditions. The best treatment by (SM 36) mutant achieved zero viable juveniles in either S or S/10 i.e, highly effective on juveniles mortality compared to the wild type of SM and untreated control which recorded 51.8, 49.3 and 49 juveniles, respectively. The numbers of non viable juveniles of the best treatment were 6, 4 and 2.8 individuals after 24, 48 and 72 hrs, respectively compared to the SM wild type which achieved 26.3. 33.3 and 27.3 while the untreated control did not show any effect on the juveniles. There were positive relationships between the nematode mortality and each of the bacteria concentration and enzyme production from the mutants. The numbers of either viable juveniles or non viable juveniles were reduced at S or S/10 dilutions and exposure periods of 24, 48 and 72 hr compared to the untreated control. This reduction was attributed to the dead nematode bodies which were degraded and destroyed by these bacterial mutants. Mutation achieved increasing of chitinase and alkaline protease-over producing mutants, which produced two to three times more endochitinase activity than the wild type of S.marcescens.

Root-knot nematode is one of the major problems that face the agricultural production of several vegetable crops. Chemical nematicides have been banned because of their healthy and environmental undesirable attributes. So, this study aimed to evaluate the potential use of sweet annie (Artimisia annua) and garden cress (Lepidium sativum) as green routes for the development of effective and eco-friendly alternative nematicides. Nematicidal activity of sweet annie and garden cress aqueous extracts (500 g/L) in the original and nano-forms were evaluated against Meloidogyne incognita in tomato planted in infected soil under greenhouse conditions. Nineteen phenolic compounds were identified in A. annua extract, which was dominated by chlorogenic acid (5059 µg/100 mL), while 11 compounds were identified in L. sativum extract, that dominated by p-hydroxybenzoic acid (3206 μg/100 mL). Nano-particles were characterized with smooth surface, spherical shape and small size (50–100 nm). Under laboratory, the nano-formulations showed mortality percentage of M. incognita J2 greater than the original extract from. Vegetative growth parameters of tomato plants treated with A. annua and L. sativum extracts significantly improved compared to the control plants. Also, biochemical analysis revealed that the extracts were able to induce tomato plants towards the accumulation of phenolic compounds and increasing the activity of defensive enzymes (protease, polyphenol oxidase and chitinase) resulting in systemic resistance. Regarding tomato fruits yield and quality, the studied treatments significantly improved the yield and physicochemical parameters of tomato fruits in terms of fruit weight, diameter, TSS, pH, lycopene content and color attributes gaining higher sensorial acceptance by the panelist. Generally, both extracts represent promising nematicide alternatives and have potential use in crop management. The nano-form of A. annua extract outperformed the nematicidal activity of other studied treatments.