Microscopic, elemental and molecular spectroscopic investigations of root-knot nematode infested okra plant roots. (December 2018) - Sharma, Neha
Abstract: Okra ( Abelmoschus esculentus (L.) Moenche) is one of the warm season crops that is grown in the tropical and subtropical regions of the world. Root-knot nematodes, Meloidogyne spp. is major constraints in growing okra crops and reduce the crop yield. The present study was aimed to perform microscopic, elemental and molecular spectroscopic investigations of root-knot nematode infested okra plant roots. The healthy, root-knot infested and root-knot infested with fungus okra roots have been studied to study the changes in chemical composition caused by infection with root-knot nematodes. We have utilized binocular spectroscopy for microscopic observations of nematode species in infected okra plant roots. Wavelength dispersive X-ray fluorescence spectrometry has been used to detect and quantify the minerals and heavy metals in healthy, nematode infested and nematode infested with fungus okra roots. Numerous major, minor and heavy elements were quantified which have shown their toxic effects in for developing root-knot nematodes in okra plant roots. We have observed the changes in the concentrations of major and heavy elements in nematode infected okra root samples as compared to healthy root samples and in particular higher contents of Ca, K, S, Ti, Sr, and Ni is detected in nematode infected okra roots than that from healthy root samples. Changes in contents of heavy metals Al and Cr were also observed in infected roots. No significant changes have been observed in the concentrations of heavy elements Br, Ni, Rb, and Zr in healthy as well as nematode infested roots. Ag and Pd have only been detected in nematode infested okra roots. Fourier transforms infrared and ultraviolet–visible spectroscopy is employed to investigate the molecular changes in the nematode infested roots as compared to healthy roots. Fourier transform infra-red spectral studies revealed the decreasing content of starch and increased level of protein contents in root-knot infested roots as compared with healthy roots. Intensity of absorption peaks appeared in diffused reflectance spectra was observed lower for infected roots and higher in healthy roots. The present study is important for further treatment strategies of okra crop to prevent the crop loss in effective manner. The authors have utilized different techniques like wavelength dispersive X-ray fluorescence; fourier transforms infrared and ultraviolet–visible spectroscopy along with optical microscopy in plant science to study healthy and infected plant samples. Highlights: For the first time, detailed spectroscopic investigations have been performed using advanced spectroscopic techniques such binocular, WD-XRF, UV–Vis and FTIR Spectroscopy to study nematode infected okra plant roots. Mineral elements and heavy metal elements associated with nematode and fungal infections have been successfully identified and quantified in okra roots. FTIR spectroscopy has been successfully used to study the changes in starch, carbohydrates, protein, fatty acids, lipids, contents in infected okra roots. We demonstrated the utility of the spectroscopic methods such as FTIR, UV–Vis and XRF for its use in plant science to explain the role of the uptake of heavy metals and to determine the role of complex molecules in diseased plants.