Management of root-knot nematode infection by using fly ash and Trichoderma harzianum in Capsicum annum plants by modulating growth, yield, photosynthetic pigments, biochemical substances, and secondary metabolite profiles

A nematicide is a type of chemical pesticide used to kill plant-parasitic nematodes. Nematicides have tended to be broad-spectrum toxicants, possessing high volatility or other properties that promote migration through the soil. In addition, the nematicides used are more expensive and have adverse effects on health and the environment, so it must use more eco-friendly and less expensive alternative methods to control root-knot nematodes (Meloidogyne incognita). Chili (Capsicum annum) suffers from nematode infestation, which reduces its quality and quantity. Therefore, the goal of this research was to assess the effect of different doses of fly ash (FA) mixed soil (5%, 10%, 15 and 20% FA) with two doses of Trichoderma harzianum (1 g and 2 g) for the management of root-knot nematode infection in chili crop. The results showed that significant enhancement in plant growth, yield, chlorophyll, and carotenoid content, protein, carbohydrate, amino acid, tryptophan, indole acetic acid, phenolics, flavonoids, proline, and nitrate reductase content of chili plants was recorded at 10% fly ash with 2 g of T. harzianum (T6). The inoculated plants registered the greatest damage with galling indexes. The lowest galling index was estimated at the T6 treatment. At higher levels of FA + combined with both doses of T. harzianum, nematode could not survive that’s why eighter galls or egg masses were observed. Nematodes may have ceased to function, lost their activity, and hence been unable to resist the stress of fly ash and T. harzianum set.  The application of T. harzianum with a lower dose (10%) of fly ash to control the nematode favored plant growth in general. In conclusion, 10% fly ash and 2 g of T. harzianum have the ability to operate as growth promoters and biocontrol agents for M. incognita.