Abstract

Foliar spray of validamycin A (VMA) controls soilborne wilt disease of tomato caused by Fusarium oxysporum f. sp. lycopersici. In the tissues of VMA-treated tomato, salicylic acid (SA) is accumulated and acidic PR-protein genes such as P4 are highly expressed, showing that VMA is an SAR (systemic acquired resistance) inducer in tomato (Ishikawa et al. 2005). However, no direct evidence to prove that the control of Fusarium wilt by VMA is due to SAR induction in tomato tissues has been presented. This time we found that a basic PR-protein gene (TOMB13GLUB encoding a beta-1,3-glucanase), a marker of jasmonate/ethylene-mediated signal cascade, was expressed in VMA-treated tomato tissues under growth chamber conditions (ca. 4000 lux), but not under glasshouse conditions (max. 45000 lux). VMA maintained its ability to control wilt disease on nahG-tomato (John Innes Centre), which carries Pseudomonas putida salicylate hydroxylase gene and can’t accumulate SA in the tissue, under growth chamber conditions. On the other hand, VMA could not control the disease on nahG-tomato under glasshouse conditions. Moreover, VMA lost its ability to control wilt disease on Nr-tomato (Tomato Genetics Resource Centre; Li et al. 2004), which is an ethylene insensitive mutant, under both conditions. These suggested that in tomato jasmonate/ethylene -mediated signal cascade is involved in the induced resistance to Fusarium wilt by VMA.