Fusarium wilt of watermelon caused by Fusarium oxysporum f.sp. niveum is the most severe disease attacking watermelon plants. Induced resistance in watermelon plants using chitosan, salicylic acid and compost was evaluated. All tested isolates of F. oxysporum f.sp. niveum were able to attack watermelon plants causing damping-off symptoms. The most aggressive isolate was isolated from Nobariya (cv. Giza 1). It caused 71.9, 46.9 and 51.6% for cvs. Gorma, Giza1 and Aswan hybrid, respectively, 30 days after sowing. Laboratory experiment results revealed that all tested concentrations of chitosan and salicylic acid significantly reduced the disease incidence under greenhouse conditions. Moreover, animal and plant compost at all concentrations significantly reduced the watermelon wilt incidence. Plant compost at 10.0 g/kg soil, chitosan at 8.0 g/kg soil and salicylic acid at 2.0 g/kg soil were tested alone or in combination to study their effect on watermelon wilt incidence and on enzyme activities of watermelon transplants. Results showed that the highest reduction in disease incidence was recorded with combined treatments between plant compost and chitosan at concentration of 8.0 g/kg soil or salicylic acid at 2.0 g/kg soil which reduced the wilt incidence by 92.9, 88.5 and 86.6% for Aswan hybrid, cvs. Gorma and Giza1, respectively. As for enzyme activities, results revealed that the highest increase was recorded with combined treatments between plant compost and chitosan at concentration of 8 g/kg soil or salicylic acid at 2.0 g/kg soil which increased the peroxidase, chitinase and -1,3-glucanase activities more than 175.0, 200.0 and 201.0%, respectively. |
