Effect of soil drenching with humic acid, L-methionine and phosphoric acid on Fusarium wilt and induction of enzymes related to oxidative stress and defense in tomato plants

Abstract

The main objective of the present study was to evaluate the efficacy of humic acid, L-methionine and phosphoric acid as a soil application for controlling Fusarium wilt disease of tomato and their effect on gene expression alterations using protein and isozyme profiling. Two isolates from each of Fusarium oxysporum f. sp. lycopersici (FOL) and F. solani (FS) were obtained from diseased tomato plants. According to pathogenicity tests, all tested isolates were able to infect tomato cultivars; cv. Super Jackal and cv. 745 under greenhouse conditions. In in vitro studies, the addition of humic acid, L-methionine and phosphoric acid to the medium at different concentrations reduced the growth of the tested isolates of the pathogens. Under greenhouse conditions, the addition of humic acid at 2%, 2 g/L of L-methionine and 0.6% of phosphoric acid to infested soil after sowing significantly decreased percentage disease severity of Fusarium wilt at both seasons (2016/17 and 2017/18). Protein bands at molecular weight 47.2 KD, 38.2 KD, 16.3 KD and 15.6 KD appeared only in treated plants. New esterase, peroxidase, chitinase and superoxide dismutase isozyme bands were detected in all treatments while not appear in the control. This results revealed that these treatments were able to induced new protein which increases resistance in tomato plants to Fusarium wilt disease.