The Effect of Chitosan and Bion on Resistance to Pink Snow Mould in Perennial Ryegrass and Winter Wheat

The effects of chitosan on resistance to pink snow mould (Microdochium nivale) were studied in young winter wheat (Triticum aestivum L.) and perennial ryegrass (Lolium perenne L.) under controlled environmental conditions. In perennial ryegrass, the putative defence activator Bion was also tested. Resistance was measured as regrowth of plants after inoculation with M. nivale and incubation in darkness at 2 C. In winter wheat, pre-treatment with chitosan at 1000 lg per plant increased resistance to subsequent infection by M. nivale, but this effect was less significant in a replicate experiment. Chitosan-treated winter wheat plants expressed the gene for the pathogenesis-related protein chitinase at higher levels than non-treated plants. Chitinase gene expression was also stimulated by M. nivale infection in winter wheat. Perennial ryegrass pretreated with Bion or chitosan and inoculated with M. nivale did not display better regrowth after incubation than non-treated, inoculated plants. Rather, regrowth was reduced in some of the Bion-treated plants after incubation. We speculate that the cost or the mechanism of induced resistance makes Bion noneffective in plants that are not actively growing. Bion at concentrations of 10, 100 and 1000 lg active ingredient per ml, and the highest concentration of chitosan used (2000 lg per ml) reduced in vitro growth of the pathogen, suggesting that both defence activators possess antifungal activity