Plant-Parasitic Nematodes (PPN) cause significant damage and losses to most of agricultural crops in the tropical and sub-tropics regions 1,2, which are estimated to be annually $100 billion worldwide 3,4. The root- knot nematode (Meloidogyne spp.) is widespread, attack a broad species of crops. It was reported that more than 3000 species of hosts which causes serious damage to most agricultural crops world-wide 4,5. The four common root nematodes species, Meloidogyne incognita, M. javanica, M. arenaria, and M. hapla are the most enormous and crop destructive nematodes 4,6.
Plant-pathogenic nematodes (Root-knot nematodes) have been found to cause crop yield losses of 8.8 % in developed countries while losses of 14.6% have been observed in tropical and subtropical countries, moreover, they invaded an array of important crops and have been found more damaging to vegetables 7,8. In the absence of effective control, M. incognita can cause total crop failure. Tomato (Solanum lycopersicum) is the most important vegetable crop widely used throughout the world and is often susceptible to the attack by Meloidogyne spp., which limits the quantity and quality of fruit yield 9,10.
Several studies reported the damage is potentially different caused by Meloidogyne spp. on different tomato cultivars under pot, microplot and field experiment conditions throughout the world 11. Yield losses of 22–30 % have been reported on tomato resulted in M. incognita infection. Yield loss in tomato due to root-knot nematode has been estimated to be up to 61.0% 12. Meanwhile, damage ranged from 32 to 40% as reported by 13.
The chemical pesticides are typically used for nematode controls. Noticeably, the overuse of such pesticides has resulted in a harmful environmental effect 14. Moreover, the extensive use of nematicides in controlling of nematodes which led to environmental and health problems and mainly increased nematode resistance. Accordingly, alternative methods of root-knot nematode management which are environmentally friendly and cost-effective are of great interest to researchers and plant breeders.
Recently, nanotechnology has been successfully applied to pest management infected plant crops 2,4,15, in addition, the use of silver nanoparticles (AgNPs) has been shown to clarify anti-nematode impacts 16. Silver nanoparticles are often synthesized by using strong and complicated chemicals 17. Thus, a considerable number of recent studies extensively focused on the feasibility of biological synthesis of environment friendly, non-toxic nanocomposites 18,19.
The use of biological materials including plant extract, fungi, bacteria, and seaweeds for the synthesis of nanoparticles showed numbers of benefits of eco-friendliness and compatibility for pharmaceuticals and other biomedical applications, as they avoid the toxic chemicals for the synthesis process 4,18,20. Among all species of algae, Chlorophyta, Phaeophyta and Rhodophyta considered most important and major groups 21. These massive varieties of seaweeds (marine algae) found to possess useful untapped biochemical compounds such as carotenoids, dietary fibers, fatty acids which might be potential source of pest control 22, In addition, the marine algae have a wide range of compounds such as agar, acids, carotenes, alkaloids, and phenolic compounds. Some of these compounds have pesticides activity 23. Antibiotics, such as bromo-phenols, tannins, phloroglucinol, and terpenoids, have anti-nematodes activity 24.
Alginate isolation from marine brown algae is a common type of crystallizing agent used in food industries, medicine, and plant pest biocontrol 25. The main advantages of alginate preparations are non- toxic nature, fast degradation, and release of microorganisms into the soil 26.
Algal alginates extracted from Colpomenia sinuosa, was tested against the M. javanica infecting eggplant (Solanum melongena L.) under green-house conditions, results revealed that these remarkable compounds significantly reduce both the development and reproduction of the M. javanica and worked in increase the growth parameters of eggplant (infected with nematode) compared to untreated infected plants 27.
Red seaweeds Corallina sp. could be review as a prospective source of bioactive molecules such as minerals and saturated fatty acids, sulfated galactans and carrageenan which displayed antimicrobial activity 28, also, they tested different algae for their nematicidal activity against M. incognita infected tomato plants; it was observed that Corallina officinalis, C. mediteranea and Ulva fasciata showed nematicidal activity against the root knot nematode M. incognita.
Recently, the development of nanotechnologies in many fields such as biology, medicine, pharmacology and as well as agriculture gave rise to the application of green silver nanoparticles as a new approach to control root knot nematodes 29,30. Khan et al. 31 reported that different seaweeds exhibited significant nematicidal activities such as: inhibition of egg hatching, increasement larval mortality and reduction of root-knot disease.
Sequency the present study was conducted to evaluate the efficiency of either Copromania sinuosa and Corallina mediterranean extracts or the synthesized green silver nanoparticles as a nematicidal activity against second-stage juveniles and mortality of M. incognita on tomato crop. Moreover, to prospect the strongest bioactive compounds in the two examined algal extracts which showed a high potency as nematicides.