www.at-spectrosc.com/as/article/pdf/202003003 110 At. Spectrosc. 2020, 41(3), 110-118 Study of Molecular and Elemental Changes in Nematode-infested Roots in Papaya Plant Using FTIR, LIBS and WDXRF Spectroscopy Neha Sharma, a Yugal Khajuria, a Virendra K. Singh, b Sandeep Kumar, c Yonghoon Lee, c Piyush K. Rai, d and Vivek K. Singh a,* a School of Physics, Shri Mata Vaishno Devi University, Kakryal, Katra 182320, Jammu and Kashmir, India b Department of Plant Pathology, College of Agriculture, Banda University of Agriculture and Technology, Banda 210001, U.P., India c Department of Chemistry, Mokpo National University, Jeonnam 58554, Republic of Korea d Department of Botany, Patna Women’s College, Patna 800001, Bihar, India Received: May 28, 2020; Revised: Jun. 16, 2020; Accepted: Jun. 16, 2020; Published: Jun. 25, 2020. DOI: 10.46770/AS.2020.03.003 ABSTRACT: Papaya is a tropical fruit of the Carica papaya plant and grown all over the world. Root knot nematodes are one of the major problems in papaya fruit crop production and causes maximum yield loss every year by slowly killing the plant. In this article, we study healthy as well as nematode-infested papaya plants at the atomic and molecular levels to obtain information about the causes and changes occurring in the plant after infestation. Microscopic observations were made to check the presence of pathogens in the plant. Elemental profiling of healthy and infested papaya plants was assessed by using two advanced spectroscopic techniques, namely laser-induced breakdown spectroscopy (LIBS) and wavelength dispersive X-ray fluorescence spectroscopy (WDXRF). The structural changes in the complex bio compounds, such as starch, protein, lipids, fatty acids, and carbohydrates, were assessed by Fourier transform infrared spectroscopy (FTIR). The elemental and molecular profiling results of the infested vs. the healthy papaya plants were compared to establish why the plants die. INTRODUCTION Plant parasitic nematodes are greatly responsible for the major destruction of agricultural crops. The annual global loss due to this infestation for most of the economically valued agricultural crops, such as vegetables, fruits, and ornamental plants, is estimated to be 14%, which amounts to an economic loss of about $80 billion worldwide. 1 Among all of the parasitic nematodes, root knot nematodes (Melodigyne spp.) are considered the leading problem for agricultural crops. Depending on the species of the nematode, type of crops and geographical region, the estimated crop loss was about 5-43% (reported in 2014). 2 The estimated crop loss (reported in 2017) due to the infestation of nematodes, particularly in India, was about ₨. 242.1 billion. 3 This infestation of the root knot nematode degrades the quality and production of agricultural foods and ultimately leads to a global loss to the agricultural industry. 4 Recently Lima et al. reviewed the negative effect of plant parasitic nematodes that are silently impacting the overall soybean yield and also presented a picture of symptoms, biology and control methods used for these nematodes species. 5 Papaya trees are susceptible to various diseases, including root rot, powdery mildew, papaya rings pot, poty virus, damping off, 6 but of the nematode diseases the two genera, namely M. incognita and M. Javanica, are reported to be the most economically detrimental. 7 Since nematode-infested plants are more prone to