Suppressive effect of marigold (Tagetes erecta) against root knot nematode, Meloidogyne incognita

Introduction

Root-knot Nematodes belonging to the genus Meloidogyne are considered the most important group of plant-parasitic nematodes worldwide attacking nearly every crop. These nematodes inflict great losses to various crops and about 5 per cent of the total world crop yield is damaged due to root knot nematodes (Sasser, 1987) [13] . Chemical nematicide is one of the most rapid method to manage nematodes, but they are detrimental to both human and environment and are relatively unaffordable to small scale farmers (Washira et al., 2009) [15] . Hence, there is a need to develop alternative method that are cheap and ecofriendly and are economically viable to the farmers. Many botanical extracts have been found to contain phytochemical such as alkaloids, tannins, saponins, flavonoids, diterpenes, glucosinolates, acetylenes and thienyls (Chitwood, 2002) [5] which are effective against plant parasitic nematodes (Adegbite, 2003) [1] . Botanical pesticides are often readily available, cheaper than the synthetic nematicides and their crude extracts are easy to be prepared even by farmers. Thus, the present investigation was done to evaluate the nematicidal efficacy of different parts (leaf, flower and root) of marigold (Tagetes erecta) aqueous extracts on nematode egg hatching inhibition and juvenile mortality of root knot nematode, M. incognita under in vitro condition.

Materials and Methods

Preparation of aqueous extracts of marigold

The different parts of African marigold (Tagetes erecta) viz., leaves, flowers and roots (var. local yellow) were used for preparation of fresh aqueous extract. It was prepared by grinding 75g of leaves, flowers, and roots with 300ml of distilled water separately. To obtain a clear and transparent extract, the aqueous extracts were filtered through a muslin cloth and then centrifuged at 4000 rpm for 10 minutes. The supernatant solution was considered as stock solution and stored it in a refrigerator for laboratory studies.

Multiplication of Root knot nematode, Meloidogyne incognita

The root knot nematode, Meloidogyne incognita required for this study was maintained as pure culture on tomato cv. PKM 1 raised in pots with sterilized pot mixture (2:1:1 red soil, sand and farmyard manure) at Dr.M.S.Swaminathan Agricultural College and Research Institute, Eachangkottai, Thanjavur.

Egg mass collection

Root-knot nematode infected tomato plant (cv. PKM 1) from the pure culture pot was up-rooted and washed gently under running tap water. Egg masses of M. incognita were picked up from the galled root using sterile dissecting needle and forceps. The collected egg masses were kept in distilled water at 10 0 C in a refrigerator to prevent hatching before application of treatments.

M. incognita egg hatching inhibition assay

The effect of different parts of marigold extract on M. incognita egg hatching inhibition was evaluated under in vitro by following the methodology suggested by Saravanapriya et al., (2004) [12] . Leaves, flowers and roots extracts of each concentration (10, 20 and 30 percent) considered as separate treatment and 3 replications were maintained. Two uniform sized egg masses of M. incognita were transferred to each treatment, while egg masses in distilled water only served as control. The experiment was laid out in completely randomized design (CRD). The number of hatched second stage juveniles was counted after 24, 48, 72, 96, 120, 144 and 168 hours (up to 7 days). The suspension from each petri plate was transferred to nematode counting dish and retain the egg masses in petri plate. The number of juveniles was counted under stereoscopic microscope under 10x. Fresh extract/distilled water was added into respective petri plates and kept again at the laboratory bench for observation.

Root knot Nematode, M. incognita juvenile mortality test

Freshly hatched second stage juveniles of M. incognita were Transferred to different cavity blocks (10 juveniles/cavity block) containing 10, 20, 30 percent concentration of leaves, flower and root extracts (3ml / cavity block), while juveniles in distilled water only served as control. For each treatment three replications were maintained. Percent juvenile mortality was counted at 24 hours intervals upto 7 days. Dead juveniles were counted under stereoscopic microscope under 10x and the mortality was confirmed by touching the juvenile with a needle. The percentage of juvenile mortality was calculated by number of dead juveniles / total number of juveniles. The data were subjected to statistical analysis using excel.

Results

Efficacy of marigold extracts on hatching inhibition of M. incognita eggs

Nematicidal efficacy of marigold (T. erecta) extracts viz., leaf, flower and roots on hatching inhibition of Meloidogyne incognita eggs was made under in vitro condition. The efficacy of marigold extracts on hatching inhibition of Meloidogyne incognita eggs showed that all parts of marigold extracts at different concentration were found to inhibit the hatching of M. incognita eggs. On the other hand, enhanced egg hatching was found in all untreated control. Highest nematode egg hatching inhibition was recorded in 30 per cent concentration of marigold root extracts (88.0 per cent) followed by 20 per cent of root extracts (59.7) within 48 hr. The effect of treatments namely, 20 percent conc. of root extracts was on par with 30 per cent conc. of leaf extracts, accounting for 59.7 and 55.3 per cent inhibition on nematode egg hatching compared to untreated control. This in vitro study showed that inhibition of M. incognita egg hatching increased with increasing concentration of marigold extracts (Table 1).

Efficacy of marigold extracts on mortality of M. incognita juveniles

The efficacy of marigold extracts on juvenile mortality of M. incognita showed that all tested marigold plant extracts of different concentration were found to be enhance the mortality of M. incognita juveniles. On the other hand, juvenile mortality was not found upto 4 days in untreated control. Highest juvenile mortality was recorded in 30 per cent concentration of marigold root extracts (88.7 per cent) followed by 20 per cent root extracts (86.7) on 7 th day. The effects of treatments namely, root extracts were on par with leaf extracts of marigold compared to untreated control respectively. The in vitro study showed that mortality of M. incognita juvenile increased with increasing concentration of marigold extracts and also increased with increased exposure time (Table 2).

[14] ; or behaving as a trap crop (Pudasaini et al., 2008) [11] . These mechanisms may occur separately or in combination resulting in lower plant parasitic nematode population. The effect of different parts of marigold extracts on egg hatching and juvenile mortality could be due to the presence of α-terthienyl and bithienyl compounds which have been reported to kill nematodes. Alpha-terthienyl is a heterocyclic, sulfur-containing compound, usually abundant in Tagetes tissue (Morallo-Rejesus and Decena, 1982) [9] and with reported nematicidal, insecticidal, antiviral, and cytotoxic activity (Arnason et al., 1989; Marles et al., 1992) [2, 7] . This in vitro study showed that inhibition of M. incognita egg hatching increased with increasing concentration of marigold extracts and exposure time. Highest inhibition on hatching of nematode eggs was recorded in 30 per cent concentration of marigold roots extracts within 48 hr. Highest juvenile mortality was recorded in 30 per cent concentration of marigold roots extracts on 7 th day. This was in agree with Hasabo and Noweer (2005) [6] who found that the mortality effect of an extract on nematode is concentration dependent. The number of dead juveniles also increased with increase in exposure time. According to Bohlmann and Herbst (1962) [3] the inhibitory effect of marigold extracts might be due to bithienyls compounds present in the freshly ground roots of T. erecta and T. patula that possess nematicidal properties. Neriman and Atilla, 2018 revealed that highest gall index was recorded from the marigold applications with only flowers and the lowest gall index was noticed from the marigold applications with green parts of the plants concluded that using of marigold in crop rotation may significantly reduce the damages caused by the root-knot nematodes.

Mali et al., 2019 [8] reported that French marigold Tagetes patula caused significant reduction in the number of root galls (8 / plant), root nematode population (29.80 / 8 galls) and soil nematode population (150.25 / 50 ml) with a remarkable growth of tomato plant (31.5 cm) as compared to other marigold cultivars and control.

Conclusion

The results of both egg hatching inhibition and juvenile mortality of root knot nematode, M. incognita under in vitro revealed that the marigold extracts are highly effective for suppressing M. incognita. Among the different parts of marigold extracts, root and leaf extracts proved to be most effective followed by flower extracts. These findings proved that different parts of marigold extract possess nematicidal activity and thus, root and leaf extracts of marigold can be used for the management of root knot nematode. It available easily inexpensive and eco-friendly.

Acknowledgement

AcknowledgmentsThe authors declare no conflicts of interest regarding this manuscript

References

1. Adegbite AA. Comparative effects of carbofuran and water extract of Chromolaena odorata on growth, yield and food components of root-knot nematode-infested soybean (Glycine max L. Merrill) [PhD thesis]. Ibadan: University of Ibadan; 2003. p. 1-120.
2. Arnason JT, Philogene JRB, Morand P, Imrie K, Iyengar S, Duval F, et al. Naturally occurring and synthetic thiophenes as photoactivated insecticides. 1989;387:164-172.
3. Bohlmann F, Herbst P. The constituents of Tagetes sp. Chemische Berichte. 1962;95(2):945-2955.
4. Brennan RJB, Glaze-Corcoran S, Wick R, Hashemi M. Biofumigation: an alternative strategy for the control of plant parasitic nematodes. Journal of Integrative Agriculture. 2019;18(0):2-12.
5. Chitwood DJ. Phytochemical based strategies for nematode control. Annual Review of Phytopathology. 2002;40:221-249.
6. Hasabo AS, Noweer EMA. Management of root-knot nematode, Meloidogyne incognita, on eggplant with some plant extracts. Egyptian Journal of Phytopathology. 2005;33(2):65-72.
7. Marles RJ, Hudson JB, Graham EA, Breau CS, Morand P, Compadre RL, et al. Structure-activity studies of photoactivated antiviral and cytotoxic thiophenes. Photochemistry and Photobiology. 1992;56:479-487.
8. Mali RS, Lavhe NV, Deotale RO, Panchbhai PR. Evaluation of different marigold cultivars against rootknot nematode (Meloidogyne incognita) under pot culture condition. International Journal of Current International Journal of Agriculture and Food Science https://www.agriculturaljournals.com Microbiology and Applied Sciences. 2019;8(5):21302135.
9. Morallo-Rejesus B, Decena A. The activity, isolation, purification and identification of the insecticidal principles from Tagetes spp. Philippine Journal of Crop Science. 1982;7:31-36.
10. Neriman K, Atilla M. Research on the effects of marigold (Tagetes spp.) on the management of rootknot nematode (Meloidogyne incognita) in nurseries. International Journal of Agriculture, Forestry and Life Science. 2018;2(2):56-61.
11. Pudasaini MP, Viaene N, Moens M. Hatching of the root-lesion nematode, Pratylenchus penetrans, under the influence of temperature and host. Nematology. 2008;10:47-54.
12. Saravanapriya B, Sivakumar M, Rajendran G, Kuttalam S. Effect of different plant products on the hatching of Meloidogyne incognita eggs. Indian Journal of Nematology. 2004;34:40-43.
13. Sasser JA. Perspective on nematode problems worldwide. In: Workshop on Plant Parasitic Nematodes in Cereal and Legume Crops in Temperate Semiarid Regions; 1987 Mar 1-5; Larnaka, Cyprus. p. 1-5.
14. Wang KH, Hooks RC, Ploeg A. Protecting crops from nematode pests: using marigold as an alternative to chemical nematicides. Plant Disease. 2007;91:35-44.
15. Washira PM, Kimenju JW, Okoth SA, Miley RK. Stimulation of nematode-destroying fungi by organic amendments applied in management of plant parasitic nematodes. Asian Journal of Plant Sciences. 2009;8(3):153-159.