Evidence of induced systemic resistance against Botrytis elliptica in lily.

Lily leaf blight, caused by Botrytis elliptica, is an important fungal disease in Taiwan. In order to identify an effective, nonfungicide method to decrease disease incidence in Lilium formosanum, the efficacy of rhizobacteria eliciting induced systemic resistance (ISR) was examined in this study. Over 300 rhizobacteria were isolated from the rhizosphere of L. formosanum healthy plants and 63 were identified by the analysis of fatty acid profiles. Disease suppressive ability of 13 strains was demonstrated by soil drench application of bacterial suspensions to the rhizosphere of L. formosanum seedlings. Biocontrol experiments were carried out with Bacillus cereus and Pseudomonas putida strains on L. formosanum and Lilium Oriental hybrid cvs. Acapulco and Star Gazer in greenhouse and field studies. Plants treated with B. cereus strain C1L showed that protection against B. elliptica on L. formosanum could last for at least 10 days and was consistent with high populations of B. cereus on lily roots. Analysis of the expression of LfGRP1 and LsGRP1, encoding glycine-rich protein associated with L. formosanum and cv. Star Gazer, respectively, revealed different responses induced by B. cereus or by the pathogen B. elliptica, suggesting that plant defense responses elicited by each follows a different signaling pathway. According to the results of biocontrol assays and LfGRP1/LsGRP1 gene expression analyses with culture filtrates of B. cereus strain C1L, we propose that eliciting factors of ISR are generated by B. cereus and some of them exhibit thermostable and heat-tolerant traits. This is the first report about ISR-eliciting rhizobacteria and factors effective for foliar disease suppression in lily.