Enhancement of defense responses by oligandrin against Botrytis cinerea in tomatoes

Oligandrin is an elicitin-like protein with a molecular mass of 10 kDa secreted by Pythium oligandrum. Here, the effect of oligandrin on defense response against Botrytis cinerea in tomato leaves is reported. Tomato seedlings were pretreated with 5 ml oligandrin (10 g/ml) by root submerging and then inoculated with B. cinerea. Disease severity was subsequently evaluated and compared with the control. Results indicate that oligandrin pretreatment reduced disease index by 78.6% on day 7 after inoculation. On day 3 after inoculation, oligandrin pretreatment caused up-regulation of peroxidases (POD), polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL) in leaves by 20.0, 5.56 and 32.88%, compared with inoculation without oligandrin pretreatment, respectively. On day 5 after inoculation, POD, PPO and PAL were up-regulated by 46.24, 32.61 and 57.14%, respectively. 24 h after the treatment with oligandrin, the expression of pathogenesis-related protein (PRs) genes, PR-2a (extracellular -1,3-glucanase) and PR-3a (extracellular chitinase), were up-regulated by 7.75 fold and 4.56 fold in tomato leaves, compared with the control, respectively. The expression of LeERF2, a member of ethylene-dependent signaling pathway, was also significantly elevated by 7.41 fold. At the same time, the expression of ethylene receptor homologue PR-6 protein was also induced. These results indicate that oligandrin can induce resistance to B. cinerea in tomatoes, and the induction of resistance involves the activation of the ethylene-dependent signaling pathway. Oligandrin is potentially useful for gray mould prevention in tomato crop.