Interactive effect of Meloidogyne incognita and fly ash on the growth, physiology, and antioxidant properties of carrot (Daucus carota L.).

Alternative methods are needed to replace chemical nematicides because they have the potential to damage beneficial soil microbial diversity. Therefore, the present work was done to elucidate the soil ameliorative, plant-growth-promoting, and nematicidal properties of fly ash. A random block-designed pot experiment was conducted during the period, December 2018-February 2019. Seeds of carrot (Daucus carota L.) were sown under natural conditions in clay pots containing a growth medium comprising of field soil amended with different levels of fly ash. Plants were inoculated with Meloidogyne incognita that were molecularly characterized using 18S and D2/D3 fragments of 28S rDNA and morphologically through perineal pattern arrangement. The results revealed that fly ash application improved the soil's important physicochemical characteristics. The inoculation of M. incognita significantly reduced the plant growth, yield, and pigment content of carrot compared to the untreated uninoculated plants. Carrot grown in 15% fly ash (85:15 w/w field soil:fly ash) growth substrate had significantly (P ≤ 0.05) improved plant growth, yield, and pigment content as compared to the untreated inoculated plants. Moreover, the proline content and the activity of superoxide dismutase (SOD) and catalase (CAT) were enhanced by applying 15% fly ash. Fly ash amendment to the soil not only improved plant growth and yield but also reduced the gall index and egg mass index per root system of the carrot as well. Our results, therefore, suggest that 15% fly ash can be used in a sustainable way to improve the growth, yield, and resistance of carrot against the infection of M. incognita.