Phenolic acids in wheat cultivars in relation to plant suitability for and response to cereal aphids

摘要

Contents of phenolic acids (PhAs) and activity of phenylalanine ammonia-lyase (PAL) were examined in uninfested and infested plants of two winter wheat cultivars differing in resistance to cereal aphids The following PhAs were determined in their freeforms in uninfested leaves of the partly resistant cv, 'Regina' and the susceptible cv, 'Zdar': p-hydroxybenzoic, vanillic, p-coumaric and ferulic acids. The level of total PhAs was higher in 'Regina' and the content of p-coumaric acid, the dominant acid in extracts, was nearly three times higher in this cultivar than in 'Zdar'. The same spectrum of PhAs was found in ears of both cultivars, and in addition, sinapic acid was detected in ears of 'Regina'. Infestation by Metopolophium dnbodum, Rhopalonphum padi and Sitobion avenae induced in leaves and ears of both cultivars an increase of PAL activity and changes in the contents of PhAs. In spite of the induction of PAL activity, the level of PhAs in the infested leaves decreased, mainly due to a decline of p-coumaric acid content. Three unidentified substances of phenolic character were found at relatively high levels in infested leaves. The level of p-coumaric acid approximately doubled in infested ears of both cultivars, but the levels of the otherPhAs were higher in 'Regina'. These results are discussed in relation to crop resistance against aphids.