Elucidating the role of fly ash in root-knot nematode (Meloidogyne incognita) suppression on okra (Abelmoschus esculentus L.): Insights into cellular viability and host defence system

In the present era of climatic shift, due to many natural and anthropogenic activities, it is imperative to use eco-friendly products to improve the soil quality and production of food crops, including okra (Abelmoschus esculentus L. Moench). As chemical nematicides are damaging to the environment, there is a need for developing alternate eco-friendly measures for the management of root-knot nematodes (Meloidogyne spp.) which cause major losses to vegetable crops globally. In this regard, a pot experiment was performed under optimal environmental conditions to study the nematicidal properties of fly ash (FA) on okra. Various grades of fly ash were applied in pots containing autoclaved soil before seed sowing. Results indicated that the application of 20% FA level (80:20 w/w field soil: fly ash) was found most beneficial for soil health, improving growth and yield traits, physio-biochemical attributes, and antioxidant properties of okra by alleviating the harmful effects of root-knot nematode (Meloidogyne incognita Kofoid and White, 1919; Chitwood, 1949) compared to other treatments. Stomatal attributes of okra also improved at 20% FA level, as demonstrated by scanning electron microscopy. Galls, egg mass formation and reproduction factor of M. incognita was significantly reduced at 20% FA level. Moreover, laser confocal microscopy combined with scanning electron microscopy revealed that 20% FA application enhanced root cell viability and detoxifies the accumulation of reactive oxygen species.