Systemic acquired resistance activation in Solanaceous crops as a management strategy against root-knot nematodes

BACKGROUND: Activators of systemic acquired resistance (SAR), such as salicylic acid (SA) and its synthetic functional analogs, benzo(1,2,3)thiadiazole-7-carbothionic acid-S-methyl ester (BTH) and 2,6-dichloroisonicotinic acid (INA), were tested on tomato, eggplant, and pepper for the control of the root-knot nematode Meloidogyne incognita. Effects on plant fitness, nematode reproduction, and root galling were screened in relation to different methods of application, to different applied dosages of chemicals, and to different plant growth stages. Dosages applied to plants were in relation to plant weights. These chemicals were also tested for their possible nematotoxic activity in vitro. RESULTS: Soil-drenches of SA and INA, and root dip application of SA and BTH, inhibited nematode reproduction, at specific dosage ranges, without affecting plant growth. SA and INA were able to reduce root galling, as well. Foliar sprays of both SA and BTH were ineffective against nematode attacks. Plants tolerated SA more than the other chemicals tested. BTH at elevated concentrations increased the mortality of nematode juveniles and reduced egg hatching in vitro. CONCLUSIONS: SAR activators at concentrations suitable for different plant growth stages and applied by the proper method can possibly be included in IPM programs for nematode management.