The influence of host genotype on the expression of induced resistance was examined in several cultivars of spring barley (Hordeum vulgare). Induced resistance was activated using a combination of elicitors (acibenzolar- S-methyl, β-aminobutyric acid, and cis-jasmone) shown in previous work to induce resistance effectively in barley. The barley cultivars examined were Cellar, Chalice, Decanter, Oxbridge, Tipple, Troon, and Westminster, which differed in their genetic resistance to two major pathogens of barley, Rhynchosporium secalis and Blumeria graminis f. sp. hordei. Controlled-environment studies showed that, although the elicitor combination reduced levels of R. secalis in all but one cultivar, the magnitude of the reduction differed among cultivars. Similar results were obtained in field experiments in 2007, 2008, and 2009, although there was inconsistency in cultivar effects between years, with the elicitor providing disease control in some cultivars in some years and not others. Use of the elicitor combination produced no significant effect on grain yield compared with untreated plants in most cases, although significant increases in grain yield were obtained with the elicitor treatment in two cultivars in 2007 and one cultivar in 2009. Analysis of the defense-related enzyme cinnamyl alcohol dehydrogenase in leaf samples from the field experiment in 2007 showed that activity of the enzyme was already high prior to elicitor application, although activity was increased further in one cultivar following elicitor treatment. It is possible, therefore, that these plants were already induced. Further work is required to confirm this and to determine whether prior induction has any bearing on the variable disease control obtained from elicitors in spring barley.
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