Acibenzolar-S-methyl-induced alteration of defence gene expression and enzyme activity in cotton infected with Fusarium oxysporum f. sp. vasinfectum

The effect of acibenzolar-S-methyl (ASM) applied in the form of Bion® as a seed soak or a foliar spray, on transcript accumulation of six defence related genes, and activities of four defence related enzymes, was assessed after cotton was inoculated with Fusarium oxysporum f. sp. vasinfectum (Fov). Significant upregulation of chitinase class I, peroxidase, and β-1, 3-glucanase transcripts occurred in the Bion® seed soak treatment with Fov inoculation compared to all other treatments. Bion® alone did not significantly increase transcripts compared with water control treatments in the majority of cases. Phenylalanine ammonia lyase transcript in Bion® treated plants following fungal inoculation was greater than in the respective Bion® alone treatments, and osmotin-like protein transcript was significantly greater in inoculated plants sprayed with Bion® than in all other treatments. Transcripts of 4-coumarate-CoA ligase-like protein were generally lower than for all other genes, and significant upregulation compared with water control occurred in extracts from Fov inoculated plants receiving no Bion® treatment, and Fov inoculated plants cultivated from Bion® treated seed. The greatest increases in chitinase, β-1, 3-glucanase and peroxidase activity occurred in root and shoot tissue from Bion® seed treated material inoculated with Fov. Bion® treatment alone did not consistently enhance enzyme activities above those measured in water treated controls. Polyphenol oxidase activities were enhanced by various Bion® or Fov treatments at 3 days after inoculation only.