Nematicidal potential of botanicals against the root knot nematode, Meloidogyne incognita

Introduction

One of the most successful multicellular creatures that parasitize practically all plants are plant parasitic nematodes (PPNs). They have an edge over other creatures in terms of their ability to live in a variety of environmental situations due to their diversification (Kern et al., 2020; Lorenzen, 1994) [5,6] . Among different plant parasitic nematodes, root-knot nematodes (Meloidogyne spp.) have a definite sexual dimorphism and a consistent life cycle. They are the most devastating biotic stressor for plants that have a negative impact on agricultural crop production (Postnikova et al., 2015) [9] . These parasitic worms have developed unique feeding habits as a result of their parasitic adaptations (Mesa-Valle et al., 2020) [7] . Nematodes that parasitize plants severely hinder plant growth, which eventually affects yield (Blaxter et al., 1998) [2] . Usually, the secondary infection causes the plant to start wilting before worm attack occurs (Desmedt et al., 2020) [3] . It has also been reported that nematode damage to the plant parts cause substantial crop yield losses by diverting nutrients, disrupting water transport and may also act as vector for viruses, which in turn mitigates the harm (Bird and Kaloshian, 2003) [1] . According to Indian estimates, crop losses would be 21.3% higher than expected, or $1.58 billion yearly (Elling, 2013) [4] . Now-a-days scientists are growing more concern about unrestrained use of chemical-based nematicides which might lead to worm resistance. Therefore, it is need of the hour to establish eco-friendly management methods. Many plant components have been found to possess anti-nematode potential (Mwamula et al., 2022) [8] . Plant extracts have been employed in certain studies to reduce PPNs damage both in vivo and in vitro. The discovery of secondary metabolites, which act as natural defence molecules in plants and, when scaled up, can prove to be a better source for nematode management, sparked the idea of controlling plant-parasitic nematodes using chemicals derived from plants. There have been numerous attempts to use plant-based remedies to manage different forms of root-knot nematodes (Shakya, 2022) [10] . Different plants have distinct effects on root-knot nematode isolates. It will therefore be necessary to search for additional plants that display anti-nematode characteristics. Therefore, the aim of this study was to evaluate the anti-nematode potential of aqueous extract of leaves from two specific plants parthenium (Parthenium hysterophorus L.) and tobacco (Nicotiana tabacum L.) against the root-knot nematode, M. incognita.

Methodology

The standard protocol described below were followed to collect root-knot nematodes, maintain nematode stocks, prepare leaf extracts, hatching of nematode eggs in occurrence of active compound, monitor hatching and inhibit hatching (if any) over a designated period of time.

Collection of parthenium and tobacco leaves

The leaves of parthenium and tobacco were collected from the nursery areas of tobacco at Bidi Tobacco Research Station (BTRS) and Nematology, BACA, AAU, Anand (Fig. 1).

Parthenium leaf Tobacco leaf

Preparation of leaves extract

The early collected fresh leaves of P. hysterophorus and middle leaves of Nicotiana tabacum was kept in paper bags. The leaves were grounded into a fine paste using a mechanical grinder. The aqueous extract was prepared by dissolving 10 g, 15 g and 20 g in 100 ml water thus making 10%, 15% and 20% solution. After mixing the sample with water, the resultant suspension was filtered using filter paper. The same process was followed with both the leaves. The filtrate was centrifuged in a centrifuge at 1000 rpm for ten minutes. The extract was removed and the supernatants collected was then dissolved in 1 ml of tap water. Without employing any plant extracts, a control treatment was kept by using just tap water.

Nematode inoculum preparation

For juveniles inocula, freshly second stage juveniles (J 2 ) were extracted after 24 hours and nematode suspension was carefully collected and J 2 count/ml water suspension was determined by counting nematodes under stereoscopic binocular zoom microscope.

Results and Discussion

The data in the Table 1 revealed that the leaves of the chosen plants exert nematode inhibition that prevents development of active Meloidogyne incognita juveniles. The anti-nematode action of the P. hysterophorus plant extract was notable, and it intensively showed highest juvenile mortality at different periodic intervals and also with the increase in the leaf extract concentrations. However, maximum juvenile mortality (92.00%) was recorded in the aqueous extract of P. hysterophorus leaves, 20% (Table 1, Fig. 2)].

The presence of various types of chemicals having lethal effect on root-knot nematode juveniles and the adverse effect of these chemicals might have further increased when the exposure period of egg hatching and larval penetration was increased. The reduction in larval penetration and hatching may also be due to the adverse effect of these chemicals which might have reduced the activity of juveniles or disrupted the host finding mechanism of the juveniles by blocking the receptor sites for receiving the chemo attractants molecules emanating from the leaves or due to loss of orientation or co-ordinated movement towards root effected by material interaction of Neuro sensory cholinesterase enzyme in nematode movement. [11] . Using 20% concentration of aqueous extracts of the weeds for more than 80% control of root-knot nematode seems effective botanical.

In vitro evaluation of leaf extracts was carried out at various concentrations for determination of least effective dose for environment friendly management of root knot nematode.

Hence, the leaves extracts of P. hysterophorus can be used to control the plant parasitic nematode M. incognita. The use of this invasive weed for developing nematicide has explored the possibility of control of the weeds.

References

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