Introduction

Root-knot nematode, (Meloidogyne spp ) are among the serious and wide spread nematode pests  attacking various economically important crops. Reduction in the quantity and quality of the crop produces results in decline in net profits. Several control practices of nematode management viz cultural methods, physical control, biological control, chemical control, use of resistant varieties etc. have been found highly effective against different nematodes. But each has its own merits and demerits But farmer mainly relied on  chemical nematicides because it effectively kill nematodes in soil . Chemical control, though gives quick control but these chemicals are not only expensive but also caused severe environmental hazards. Some fumigant nematicides have been banned since year 1979 (DBCP) by Environmental Protection Agency as environmental toxins 2005.  Therefore there is an urgent need to replace pesticides with alternative means of control that are less toxic and more eco friendly. Other convential methods for nematode control like cultural, physical, biological and plant resistance, which too have technical and operational limitations of one kind or other. The use of non-hosts and antagonistic plants  having allelopathic effect offers an promosing area for combating and managing root-knot nematodes. Plant parts and their products have been found to posses nematicidal and nematostatic properties against plant parasitic nematodes. Nematicides of plant origin contains iso-thiocyanates, thiophenics, glucosides, alkaloids, phenolics and fatty acids in their different plant parts which are fatal to nematodes. Thus, the present investigation was done to evaluate the nematicidal effect of aqueous extract of medicinal against egg hatching and larval  mortality of Meloidogyne incognita.

Material and Methods

Preparation of  Aqueous Plant Extracts

Healthy leaves of one year old plant of turmeric  (Curcuma longa), marwa tulsi  (Origanum majorana), mint(Mentha arvensis ), aonla  (Phyllanthus emblica)  and jatropha (Jatropha curcas)  were collected from herbal park of  CCSHAU, Hisar (Haryana) These collected plant leaves were washed with steriled distilled water.The aqueous extract of these plants were prepared separately by grinding and dissolving 2 g of ground material in 5 ml of distilled with the help of pestle and mortar. To obtain a clear  and transparent extract, free of all plant debris , the water extracts were filtered through a four ply muslin cloth and then centrifuged for five minutes at 4000 rpm and then filtered through a Whatman’s filter paper .The aqueous extracts thus prepared  were kept in  covered flasks in refrigerator and were taken as stock solution for evaluating their nematicidal effect on hatching and larval mortality under  in vitro condition.

Table 1: Effect of aqueous extracts of plants against nemic mortality

C.D. at 5 %    Aqueous extract of plants (P) =(1.31)

Concentrations (C.) =(1.43)

P x C = (3.20)

Figures in parenthesis are angular transformed values

In vitro testing for nematode mortality

Five ml. of suspension containing approximately 100 freshly hatched juveniles of root-knot nematode, M.incognita were taken in 50 mm size petriplates. Measured quantity of stock solution was added to each petriplate to make the resultant dilutions of 1:5, 1:10, 1:20, 1:40, and 1:80. Each dilution was replicated three times. These petriplates were kept in BOD incubator at 25±1^°C. Larval mortality after 48 hrs exposure of the larvae to different dilutions of different oils were recorded by counting living and dead second stage juveniles under stereoscopic binocular microscope. Juveniles put in distilled water  were treated as control. Larvae that did not respond to touch by a fine needle were counted as dead. Percent larval mortality was calculated and data thus, obtained was subjected to angular transformation and analysed by applying CRD factorial design.

Testing for egg  Hatching     

Egg masses of root-knot nematode, M.incognita were collected from infected brinjal roots and washed with steriled distilled water. The similar sized egg masses were kept in 50mm petri-dish (4 egg masses/ petridish) and measured quantity of stock solution was added to each petriplate to make the resultant dilutions of 1:5 and 1:20. Each dilution was replicated three times .These petriplates were kept in BOD incubatorat 25±1^°C .The number of juveniles hatched after 3, 6, 9 and 12 days of exposure to different dilutions  were counted under stereoscopic binocular microscope. Egg masses put in distilled water  were treated as control.

Results and Discussion

Experiments were conducted to study the effect of  aqueous extracts of different plants  on hatching and mortality of M.incognita larvae under laboratory conditions

Effect of Aqueous Extracts  on  Nemic Mortality

Aqueous extracts of all the plants were found lethal to juveniles of M. incognita. Rate of mortality was directly proportionate to concentration of extracts. The highest mortality of larvae was observed at 1:5 dilution of extracts of tested plants while lowest was observed at lowest dilution i.e. 1:80(table1). Among extracts maximum  per cent larval mortality was recorded with mentha i.e. (83.83) followed by turmeric (80.56 ) marwa tulsi (80.25) at 1:5 dilution respectively. The extract of mentha was found consistent in terms of larval mortality as it was effective  up to 1:40 dilution but showed low mortality at 1:80 dilution.

Effect on egg hatching                                                                 

All plants extracts showed inhibitory effect on egg hatching . The rate of hatching was inversely proportional to concentration of extracts and exposure period, as it decreased with increase in concentration. The maximum hatching of eggs was observed in 1:20 while lowest rate at 1:5 dilution in all extracts tested (table 2). Among aqueous extracts , extracts obtained from mentha showed most inhibitory effect followed by turmeric and marwatulsi respectively. Minimum hatching was recorded with  mentha followed by turmeric  and marwa tulsi after 12^th day. The maximum egg hatching was recorded at 3^thday in water. It is revealed from table 2 that all three factors viz, aqueous extracts, their concentrations and exposure time significantly affected hatching individually as well as in combination with one another.

Table 6: Effect of aqueous extracts of plants on the egg hatching of root –knot nematode , Meloidogyne incognita (Average of three replicates)

C.D. at 5%   Aqueous extracts  of plants (P) = (0.07),  Conc(C).=(0.05),   Exposure period (T)= (0.06) , PxC=(0.12), PxT=(0.14), CxT= (0.11), PxCxT=(0.24)
Figures in parenthesis are √n transformed values

The present investigation are in adjustable conformity with the finding of Prasad and Suverna (2005), who while testing four concentrations of root and leaf extracts of C.procera and P. hysterophorus (0.5, 1.0, 2.0 and 4.0% at exposure periods of 24, 48 and 72 hrs) against reniform nematode reported higher mortality of pre-adults of R..reniformis race-A infesting sunflower cv. Morden as compared to the control. Similarly, Goel and Gupta (2004) also reported the nematicidal potential of onion cv. N-53 extract against second stage juveniles of M. javanica. The root extract of onion at 100 per cent concentration with 48 hrs exposure time caused the highest larval mortality followed by leaf and bulb extracts of the sameconcentration. While evaluating the nematicidal properties of 15 plant and their various parts viz. Albizzia amara, Aristalochia bractiata, Tagetes erecta, T. patula, Origanum majorana, Azadirachta indica, Butea monosperma and Calotropis gigantea leaves, Acorus calamus roots, Allium sativum bulbs, Citrullus lanatus, Areca catechu and Anona reticulate seeds, and C. gigantea and Carica papaya latex against the root-knot nematode, M. incognita egg masses, Saravanapriya et al. (2004) reported that the seed extract of A. catechu showed highest inhibition rate at 0.1 per cent concentration. The latex of C. papaya caused 98.22 and 100 per cent hatching inhibition at 1.0 and 10.0 per cent concentrations, respectively. The latex of C. gigantea also caused 100 per cent inhibition at 10.0 per cent concentration. In the present investigation observations showed the nematicidal activities of plant extracts resulting inhibition of hatching and mortality of larvae of    M.incognita.

Conclusion     

Nematicides of plant origin include iso-thiocyanates, thiophenics, glucosides, alkaloids, phenolics and fatty acids( Grainge & Ahmed ,1988).. Use of botanicals is now emerging as one of the important means to be used in protection of crop produce and the environment from pesticides pollution, which is a global problem Therefore it is important to examine new plants or new varieties of plants for their efficacy in immobilizing, retarding development or killing nematodes.The intensive use of synthetic pesticides and their environmental and toxicological risks have generated increased global interest in developing alternative sources of chemicals to be used in safe management of plant pests . These compounds can be developed for use as nematicides themselves, or can serve as model compounds for the development of chemically synthesized derivatives with enhanced activity and reduced environmental impacts. These antagonistic plants are excellent candidates because they can be used for developing as nematicides themselves, or they can serve as model compounds for the development of chemically synthesized derivatives which enhanced activity or environmental friendliness (Chitwood, 2002). Nematicidal bio-active products of plants, being less persistent in environment, are safer for mammals and other non target organisms. Botanical pesticides are often readily available, cheaper than the synthetic counter parts and their crude extracts and are easy to be prepared even by farmers. They reduce the chances of development of resistance or resurgence in pests. Hence, in light of the the above information, the present investigation were proposed to be undertaken to investigate the role of a few nematoxic plants in the management practices which are economically and recofriendly in nature ensuring environmental safety

References

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