Studies on effect of gold nanoparticles on Meloidogyne incognita and tomato plants growth and development

The plant parasitic nematodes are one of world major agricultural pest, causing in excess of 157 billion dollars in worldwide damage annually. This study has provided evidence that gold nanoparticles have great utility for management of root-knot nematodes in tomato crop. The effect of gold nanoparticles on Meloidogyne incognita J2 was remarkable under the direct exposure in water, after three hours of incubation of Meloidogyne incognita with GNPs showed the 100% mortality. The lesser survival rate of Meloidogyne incognita in soil treatment showed the strong nematicidal effect of gold nanoparticles. Subsequently, the pot experiment had shown the beneficial effects of gold nanoparticles for intensively managing the root-knot nematode. The Pot experiment not only showed us that GNPs were lethal to root-knot nematodes were also induces growth of tomato plants and didn’t have any kind of negative impact on plant growth. In our study, GNPs were found to be safe and lethal to Meloidogyne incognita.


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The bio-gold nanoparticles synthesized by microbes are the result of various molecular strategies to overcome 24 the mental stress by decreasing redox state of metal electron shuttle which can be extracellular or intracellular, 25 leading to the conversion of gold metal ions to nanoparticles of defined shape and size (Konishi et al., 2006).

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The biosynthetic approach is particularly significant over the chemical synthesis leading to generation of toxic 27 substances and expenditure of heavy metal and the nanoparticles have a tendency to clump together and are 28 rendered useless nanoparticles produced by physical method are unstable and tend to agglomerate (Ali et al.,

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Meloidogyne incognita is a nematode belonging to family Heteroderidae and is commonly known as root-knot 41 nematode as it prefers to attack the root of its host plant. It has worldwide distribution and numerous hosts. root cells and establishes giant cells. The roots become gnarled or nodulated, forming galls, hence the term 44 "root-knot" nematode (Pline et al., 1988

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In vitro synthesis of gold nanoparticles by indigenous Bacillus licheniformis strain GPI-2 60 Extracellular biosynthesis of gold nanoparticles was carried out using supernatant of Bacillus licheniformis 61 strain GPI-2, treated with 1mM gold chloride solution followed incubation at 37oC and to achieve maximum 62 gold nanoparticles activity, the time range of 0-240 hrs was investigated.

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Microcup was washed with 100% absolute ethanol. 10 ul samples was filled in a 2 mm internal diameter micro-69 cup and loaded onto the FTIR set at 26°C ± 1°C. The samples were scanned in the range of 4,000 to 400 cm−1 70 using a Fourier transform infrared spectrometer (Thermo Nicolet Model 6700, Waltham, MA, USA). The 71 spectral data obtained were compared with the reference chart to identify the functional groups present in the 72 sample.

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Transmission electron microscope 74 A drop of the sample was applied to a carbon coated copper grid. After about 1 min, the excess solution was 75 removed using blotting paper and the grid was air dried before analysis.

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The direct vulnerability of Meloidogyne incognita 77 Germination of tomato seeds

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To study the nematicidal effect the bio gold GNPs prepared as above Solanum lycopersicum were prepared 79 from Departmental of Vegetable Science DR YSP UHF Nauni. Thus seeds were shown in pot tray containing 80 autoclaved sand and topsoil (1:2) for germination. The seedlings after reaching two leaf stages were transplanted 81 into plastic pots containing a similar mixture as above. In this manner, 60 seedlings were transplanted into 60 pots and these were maintained in the greenhouse to be used for further bioassay of nematode egg hatch and

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Nematode mortality rate was measured with an inverted microscope. After every 30 minutes, samples were 99 checked for the mortality and their rate was recorded to determine the effective dose required for affecting 100 nematodes. Healthy nematodes were defined as those were curled where as vulnerable or unhealthy nematodes 101 were defined as those that appeared stiff or straight bodies.

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Soil treatment with gold nanoparticles:

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The soil was inculcated with M. incognita. The water saturation level of the 50 cm3 soil sample was 104 predetermined to be 25ml. The total was homogenized divided into 50 cm3, placed into a plastic container and 105 then saturated with 25ml. gold nanoparticles solution at 0,300,600,900,1200,1500 ul. The samples were 106 arranged in a completely randomized design with five replicates and incubated at room temperature for one to 107 ten days. After the designated exposure time nematodes were extracted after from samples using Baermann tray 108 system. After 48 hrs submergence in water, the samples were then poured into sieve filtered M. incognita were 109 counted using an inverted compound microscope.

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Estimation of photosynthetic pigments 120 Photosynthetic pigments (chlorophyll a) in leaves were assayed according to Hiscox and Israelstam (1979). The

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The direct vulnerability of Meloidogyne incognita to gold nanoparticles in cavity block experiment

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The direct vulnerability of Meloidogyne incognita to gold nanoparticles in water was evaluated and it was found 167 that gold nanoparticles increased the mortality of Meloidogyne incognita effectively and efficiently. After one 168 hour of application of GNPs mortality was initiated and 100% mortality has been achieved after three hours. It 169 was observed that after application of gold nanoparticles crystallization of water occurred even at room temperature followed by clumping or aggregation of these nematodes leading to mortality. T-4 treatment 171 consists of 400µl of bio gold nanoparticles found to be highly effective to cause the maximum mortality 172 whereas in case of control no mortality has been found ( figure-5a, b).

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It has been observed that only 36% seed germinated in control samples. Seeds treated with 100 µl of biogold 203 nanoparticles showed 58% germination and seed germination increased to 66% in T-2 treatment. The result has 204 been obtained with respect of tomato with increased fresh weight by T-2 treatment following by T-1 treatment 205 as compared to control. The dry weight data was also found to be similar with fresh weight data (Figure-20a, b).

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The results obtained from the in vivo experiment effect of biogold nanoparticles Bacillus sonorensis KRI-7 of 207 both plant species was found to produce a very significant increase. In case of Solanum lycopersicum shoot

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In the present investigation, we have found that gold nanoparticles significantly increased the seed germination

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The present investigation has provided evidence that gold nanoparticles have the highest rate of mortality and 268 were effective for management of root-knot nematodes (Cromwell et al., 2014) reported J2 of M. incognita were 269 exposed to AgNPs in water at 30 to150ul/ml, 99% nematodes became inactive in 6 hrs.    nanoparticles on the physiology and nutritional quality of radish sprout and suggested that nAg could 307 significantly affect the growth, nutrient content and macromolecules conformation in radish sprouts. When the 308 seedling was exposed to 500 mg\L had 901mg AG\Kg dry weight and significantly less ca, Mg, B, Cu, and Zn, 309 compared with control. They also revealed that changes occur in lipids, proteins and structural components of