Evaluation of plant stage dependency of QTLs to homologous and heterologous rust pathogen isolates of barley

A disease test at different leaf layers (plant stages) of homologous rust and heterologous rust species were studied. The result from homologous rust species showed that those quantitative trait loci (QTLs) (Rphq2 and Rphq11) which were effective at seedling stage were also effective across all plant stages with gradually decreasing effect as plants grew older. Rphq3 which had consistent effect in all leaf layers confirmed the same result, that it is a plant stage independent QTL. For heterologous rusts, the effect of Rnhq-V was studied on three rust species; P. hordei-murini (Phm), P. hordei-secalini (Phs) and P. triticina isolate ‘Flamingo’ at three stages (leaf layers). Infection frequencies are higher at seedling stage and dramatically decrease as plants grow older in all three rust species tested on both SusPtrit and Su-Rnhq-V. The difference between lines tends to be reduced with higher leaf layer in all three tested inappropriate rust species. However, this would be not because of less effectiveness of the Rnhq.   Key words: Plant stage, homologous rust, heterologous rust.