Background: Soil heavy metal pollution is an important environmental concern that has serious adverse effects on soil biota. The present study is aimed to assess the toxicity of heavy metals; lead (Pb) and nickel (Ni) on the biochemical and immunological parameters of Eudrilus eugeniae. Methods: Adult earthworms were exposed to various sub-lethal concentrations of Pb and Ni along with their combinations. After exposure for a period of 90 days, the content of bio-molecules such as carbohydrates, crude lipids and crude proteins; the total number of coelomocytes and the number of different types of coelomocytes were determined. Result: The results showed that the bio-molecular content decreased gradually and the maximum decrease was recorded in T6 (Pb 0.06 ppm) followed by T9 (Ni 0.03 ppm+Pb 0.03 ppm). Similarly, a decline in the total number of coelomocytes and the number of different types of coelomocytes was observed in a dose-dependent manner. Structurally five different types of coelomocytes were distinguished: granulocytes I, granulocytes II, amoebocytes I, amoebocytes II and eleocytes. So, it can be concluded that heavy metals are highly toxic to earthworms and biochemical and immunological parameters can be used in environmental monitoring programs.

Virulent fungal plant pathogens are a serious threat to crop productivity and are considered a major limitation to food security worldwide. To meet these challenges, pathogen detection is crucial for taking appropriate measures to curb yield losses. Disease diagnosis at an early stage is one of the best strategies for crop protection. Earlier, traditional methods were used to diagnose and manage fungal diseases, which included visual scouting of the disease symptoms and spray of fungicides. The utility of immunoassays for early detection and precise identity has been appreciably stepped forward following the improvement of enzyme-connected immunosorbent assay (ELISA) and monoclonal antibodies. Nucleic acid-based diagnostic techniques have turnout to be the preferred type because of their greater speed, specificity, sensitivity, reliability, and reproducibility. The biosensor eliminates the need of sample preparation and can be used for on-site detection of fungal pathogens at latent infection stages so that preventive measures can be taken. Currently, multiple human and animal diseases have been detected with the help of biosensors. However, reports on plant pathogen detection using biosensors are still in infancy. Despite many applications of antibodies, there are also multiple drawbacks, including high cost, low physical and chemical stability, and the ethical issues associated with their use. Now, DNA based biosensors are gaining popularity because of their sensitive and precise detection of DNA target sequences. Immunological and DNA-based techniques combined with nanotechnology offer highly sensitive and selective gel-free detection methods, and the lab-on-chip (LOC) feature of biosensors makes them a very reliable tool in crop protection.

Soil heavy metal pollution is widespread and has severe adverse effects on soil organisms. Earthworms are the major soil organisms which perform several beneficial ecological functions butare vulnerable to damage from heavy metal pollution of soil. The present study was conducted to evaluate the potential toxicity of arsenic (As) and chromium (Cr) on the biochemical response of the earthworm, Eisenia fetida. Following exposure to various sub-lethal concentrations ofAs (34, 68, 102 and 136 mg/kg) and Cr(26, 51, 77 and 102 mg/kg ) for 28 days, the levels of several biochemical markers, including superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), Glutathione-S-transferase (GST) and malondialdehyde (MDA) content were assessed. The results showed that both heavy metals significantly (p<0.05)  impacted the antioxidant enzyme activities and MDA content during the entire exposure period. Compared with the control, SOD, CAT, POD and GST activities increased significantly (p<0.05) by (6.21-23.23, 6.32-18.6, 15.87-34.18 and 0.84-5.45% respectively) at14th day, but after prolonged exposure, these activities were significantly (p<0.05) decreased (9.58-38.13, 10.09-30.03, 19.05-53.16 and 2.26-9.36% respectively) at 28th day. The contents of MDA showed significant (p<0.05) increase (17.84-45.59%) in all exposure groups for entire exposure period. Therefore, it can be concluded that antioxidants play a direct role in the adaptive response of E. fetida for survival in heavy metal contaminated soil. This adaptive antioxidant response can be used as an important biomarker to assess the toxicity of heavy metals in the soil ecosystems.