Identification of induced resistance responsive genotypes in tomato by various plant defense activators

Abstract

Breeding lines of Solanum lycopersicum were identified as highly or weakly responsive to the plant defense activators, benzo(1,2,3)thiadiazole-7-carbothioic acid-S-methyl ester (BTH) and para-aminobenzoic acid (PABA), against Pseudomonas syringae pv. tomato. Breeding line 7024 was highly responsive to seed-applied BTH and foliar-applied PABA, whereas lines 7007 and 7008 were weakly responsive to BTH and PABA, respectively, when applied similarly. Expression of three SAR-related genes was examined for those lines, but the only differences were that SlPR1a was induced more for line 7024 by BTH and SlPR3b and SlPAL5 were induced and SlPR1a was primed more for line 7024 by PABA. Expression of the ISR genes, SlPin2 and SlPR2b, showed no induction or priming by BTH or PABA. The effectiveness of both BTH and PABA for inducing resistance was affected by plant gentoype, which was correlated with changes in some but not all plant defense gene expression levels.