Potential Elicitors for Avenalumin Accumulation in Oat Leaves.

Abstract

Chitin, chitosan, oligo galacturonic acid, glucan and some of constituent monosaccharides were tested of their elicitor activities for avenalumin accumulation in oat leaves and a bioassay method for its elicitation was evaluated. Among the compounds tested, a water-soluble chitosan (DP: 37, acetyl, rate 39%) was the most potent elicitor, followed by chitin, glycol chitin, oligo galacturonic acid and glucan in the order. No accumulation of avenalumin I was elicited by aminosugar monosaccharides. Effects of the molecular size and acetylation rate of chitosan on elicitor activity were determined using chitosans with DPs 37, 10, 8 and 5, and acetylation rates 39, 30, 15 and 6%, respectively. All the chitosans were effective elicitors; however, the high molecular chitosan (DP: 37) seemed to be more active elicitor than the others especially at low concentrations. A significant finding was that the chitosans elicited a differential pro-duction of avenalumin I in oat cultivars of different genetic backgrounds. Certain cultivars such as Shokan-1 and Pc-51 were always sensitive to the chitosans and accumulated larger quan-tities of avenalumin, whereas a cultivar like Pc-45 accumulated only about 1/4 the amount in the sensitive cultivars. It was shown that infiltration of elicitor solutions into intercellular spaces of the primary leaves by hypodermic injection was found much more efficient for the assay of differential elicitor activity than the assay with epidermis-detached leaf segments.