M. F. Abdel- Monaim
Fusarium wilt caused by Fusarium oxysporum f. sp. lycopersici is the most serious diseases attacking tomato plants. The objectives of the study were to determine the effect of SA, H2O2, ethephon and mannitol as resistance inducers in tomato plants against Fusarium o. f. sp. lycopersici and to provide new strategies to control the wilt disease of tomatoes. For that, the effect of these four chemicals inducer, at different concentrations (50, 100, 200 ppm), on severity of the tomato wilt as well as fungal growth and spore formation was investigated. These inducers were applied with two methods, seed soaking and seedling soaking. Generally, all the tested chemical inducers reduce disease severity, the highest reduction in diseases severity was obtained with mannitol and SA at 200 ppm followed by H2O2 at 200 ppm, while Ethephon lower treatments for reduce disease severity. Seed soaking in mannitol gave the highest reduction of damping- off and wilt caused by the tested Fusarium isolates. Also, this inducer recorded the highest reduction in the area under wilt progress curve (AUWPC) from 1125 and 1024 in control to 156.7 and 124.2 in treatment. Seed soaking in these chemicals induced systemic resistance in seedling stage, whoever seed soaking in mannitol at 200 ppm gave the highest protection against to infection caused by both Fusarium isolates (92.14 and 92.72% protection). On the other hand, seed soaking in these inducers at all concentrations increased of seed germination, seedling height, fresh weight and dry weight. In vitro studies, all resistance inducers inhibited growth of both Fusarium isolates especially at high concentration (200 ppm). Hydrogen peroxide exhibited the highest effective to suppress dry weight and leaner growth of both tested fungal isolates followed by SA, however SA gave the highest reduction of spore formation followed by H2O2. Mannitol showed the lowest effect in all aspects. It could be suggested that mannitol and salicylic acid used as seed soaking or seedling soaking could be used for controlling wilt disease of tomato plants since they are safe, low cost and effective against the disease.
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