Influence of Edaphic Factors on Root-Knot Nematodes, Meloidogyne sp. infesting Carrot (Daucus carota) Grown in Tamil Nadu, India

Root malformation is the major issue in the supply chain of carrots at micro and macro market levels. Root knot nematodes, Meloidogyne spp. play a pivotal role in the formation of distorted carrot roots with irregular shapes. The present study revealed that Meloidogyne incognita and M. hapla damage the roots of carrots in the tropical and temperate regions of Tamil Nadu respectively and the former is more notorious than the latter. M. hapla was found to be predominant in the carrot ecosystem of high altitude and cooler climate of Tamil Nadu with acidic pH and high organic matter, whereas it is vice versa in case of M. incognita. Soil population of second stage juveniles (J₂) of Meloidogyne spp. showed a positive correlation with soil moisture, sand per cent, porosity, phosphorus, potassium and a negative correlation with soil temperature, pH, organic carbon, silt and clay per cent and electrical conductivity (EC). Responses of Meloidogyne spp. to nitrogen showed strikingly different correlations with divergent ecosystems (r= 0.64, -0.43). Meloidogyne spp. had the highest affinity to soil moisture (r = 0.82, 0.84) as increased population of Meloidogyne spp. was observed with the increased moisture in the soil, whereas soil temperature had negative impact on the population of Meloidogyne spp. (r = -0.87, -0.88).