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Efficacy of Nemagold in the control of plant parasitic nematodes in different cropsqrcode

Dec. 17, 2019

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Dec. 17, 2019
Nematodes are among the widespread organisms on earth. They are capable to colonizing any ecosystem, including extreme environments, such as deserts, hot spring waters, artic lands and polar seas1. The capabilities of nematodes to colonize any ecosystem are related with their multiple lifestyles. Many species are free-living (Bacterial and fungi eaters and predatory nematodes). Other have the ability to parasitize organisms including animals, insects and plants (plant parasitic nematodes)2.

Plant parasitic nematodes (PPNs) affect all major crops such as fresh vegetables, cereals, grass plants and fruit trees. In general, the principally damage caused by PPNs are patches of stunted, chlorotic plants within a field, reduced size and number of leaves. By the same way, the infection of susceptible plant roots by root-knot nematodes (RKN) results in the formation of swellings (galls) on the roots (Fig. 1). Additionally, the normal transfer of substances from roots to the plant top is restricted, resulting in wilt and nutritional deficiencies and poor yield. Sometimes different species of nematodes could affect the same crop at same time increasing the damage to the plant.

The presently, more than 4100 species of PPNs have been described, being the most economically important the root-knot nematodes of genera Meloidogyne spp. and the cyst nematodes (CNs) from Heterodera spp. and Globodera spp.3. Other important nematodes are the Root lesión nematodes, Burrowing nematodes, Root feeding nematodes and Reniform nematodes. The damage caused by PPNs is estimated in more than 80 billion of dollar in worldwide agriculture anually4.

Plant pest control in the agricultural sector requires new alternative products that meet food and environmental safety care requirements. In Atlantica Agrícola we have been developed alternatives to chemical pesticides.

One of the strategies is the exploration of a diversity of plants and their metabolites in order to obtain new natural agents, these natural pesticides are denominated botanicals. Botanicals with pesticidal properties have been demonstrated to be an important source of compounds such as polyphenols, terpenes, flavonoids, alkaloids, saponins and coumarins which are used as raw materials in the development of new protective agents. Tagetes spp. (Asteraceae), is currently recognized as one of the most promising plant species given its diverse biological activities against some pests such as ticks and PPNs. Therefore, in this work we review the effects of Tagetes spp., extracts that have shown biological activity against pest insects or PPNs.

First, we carried out experiments in order to evaluate the concentration of metabolites with nematicidal properties of different crude extracts of roots, stem, leaves and flowers. We evaluated the content of polyphenols by HPLC (high performance liquid chromatography) obtained differences between crude extracts, being the leaves and stems the shorter concentration (10-50 ppm). On the contrary, the roots and flowers contained the higher concentration of polyphenols (120-600 ppm) principally glycosides flavonoids and phenolic acids. In the same way, Volatile compounds (VCs) were isolated and identified by UPGC (upper performance gas chromatography) in crude extracts from Tagetes spp. we obtained high concentrations from 40-100 ppm of VCs (Tiophene and Limonene) using different organic solvents.

Consequently, we have evaluated the effects of that crude extracts against different nematode development stages in-vitro, greenhouse and field experiments.

In-vitro we have evaluated the effect on hatching of Meloidogyne spp. eggs and mortality rate of juveniles (J2). In these experiments, we carried out applications of different concentrations of our botanical nematicide Nemagold (Tagetes spp. + Ascophyllum nodosum). We founded similar results between Nemagold and chemical nematicides (with not significantly differences), when we increase Nemagold concentration the egg hatching was reduced even more than 80 % in comparison with control treatment (distilled water). Furthermore, we found affectations on egg cuticle that produced damage and death of embryos (Fig. 2).

Fig 2. a) Meloidogyne egg in distilled water (Control treatment) normal formation of embryo.
b) Damage on egg cuticle (Meloidogyne spp.) caused by Nemagold 24 h after incubation, black arrows indicates damage zones and embryo death
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In greenhouse experiment, we evaluate the efficacy of Nemagold on the management of Meloidogyne spp. populations in tomato. In this experiment we infected tomato plants with 10,000 eggs of Meloidogyne spp. Then, we irrigate the plants each 15 days (during 60 days) with different doses of Nemagold or chemical nematicide. The control plants were irrigated only with nutritional solution. After 2 months, we obtained the tomato roots and evaluated the damage caused by Meloidogyne spp. Here, we found that the number of egg masses or eggs by root was significantly reduced respect to control plants (8500 egg/ root and 750 masses/root). In plants irrigated with Nemagold we quantified 27 egg masses and 1900 egg/ root and finally in plants irrigated with chemical nematicide we found the minor number of egg masses and egg/root with only 10 egg masses and 260 eggs by root.

Finally, in a field experiment we evaluated the effect of Nemagold in the control of Meloidogyne spp. populations in eggplants. We irrigate plants with nematicides 3 times (each 15-20 days) and 4 months after sowing we evaluate the yield and gall index. We have not found significantly differences between Nemagold and chemical nematicide. Plants irrigated with Nemagold and chemical nematicide displays the minor gall index (Fig 3).

Fig 3. Gall index in eggplant roots. Control plants display major gall index respect to Nemagold (Tagetes spp 1) and chemical nematicide.

This study demonstrates the relevant nematicidal activity of Nemagold. Therefore, the continuation of research in the area of botanicals is very important to contribute to the generation of new products that will provide alternatives to conventional chemical agents.

1. Yeates, G.W. (2004) Ecological and behavioural adaptations. In: Nematode Behaviour (Gaugler, R. and Bilgrami, A.L., etc.), pp. 1–24. Wallingford, Oxfordshire: CABI Publishing.
2. Decraemer, W. and Hunt, D.J. (2013) Structure and classification. In: Plant Nematology (Perry, R.N. and Moens, M., etc.), pp. 3–39. Wallingford, Oxfordshire: CABI Publishing.
3. Jones, J.T., Haegeman, A., Danchin, E.G.J., Gaur, H.S., Helder, J., Jones, M.G.K., Kikuchi, T., Manzanilla-L_opez, R., Palomares-Rius, J.E., Wesemael, W.M.L. and Perry, R.N. (2013) Top 10 plant-parasitic nematodes in molecular plant pathology. Mol. Plant Pathol. 14, 946–961.
4. Nicol JM, Turner SJ, Coyne DL, Ld Nijs, Hockland S, Maafi ZT: Current nematode threats to world agriculture. In Genomics and Molecular Genetics of Plant-Nematode Interactions. Edited by Jones J, Gheysen G, Fenoll C. Netherlands: Springer; 2011:21-43.


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