Phytochemicals’ Classes Involved in Nematode Defense and their Related Activities

Plant parasitic nematodes (PPNs) are one of the most lethal pests that have emerged in the past years. These nematodes are microscopic in size, cylindrical in shape, and inhabit mostly terrestrial ecosystems. They account for a significant biotic limiting factor that hampers crop yield and productivity. PPNs are majorly categorized into three categories such as lesion nematodes (<i>Pratylenchus</i> spp.), Root-knot nematodes (<i>Meloidogyne</i> spp.), and cyst nematodes (<i>Heterodera</i> and <i>Globodera</i> spp.). They are known to be the primary cause of pest infestation among other PPNs. Terpenes, flavonoids, alcoholics, and phenolics are essential plant secondary metabolites with a reliable potential to control the PPN population. Reports have shown that they reduce the gall size, inhibit egg hatching, increase the mortality rate of infective juveniles (IJs), <i>etc</i>., which lead to the death of IJs and hence protect the crops against PPNs. Such studies elucidate the importance of using plant phytoconstituents as a natural alternative to hazardous chemical pesticides, which are dangerous to humankind and nature. This chapter culminates the efficiency of plant secondary metabolites and their significance in killing root-knot nematodes majorly of different species infesting commercial agricultural crops at different life cycle stages.