The effect of genetic variation in barley on responses toRamularia collo-cygni

摘要

The effect of mlo resistance to powdery mildew on the responses of barley seedlings to Ramularia collo-cygni was studied in relation to light intensity before inoculation. It had previously been found that mlo alleles were associated with reduced severity of Ramularia leaf spot (RLS) in field trials while high light intensity before inoculation increased the disease in seedlings. In a cross-over experiment, plants were grown at three light levels before inoculation then placed in each of the three light levels after inoculation. As in previous work, light intensity before inoculation increased the severity of RLS, but in contrast to previous results from field trials, the mlo5 allele was associated with increased RLS levels, while the effect of higher pre-inoculation light intensities on enhancing RLS was stronger in mlo5 plants than in those with the Mlo mildew-susceptibility allele. It is proposed that the effect of elevated light intensity on enhancing RLS in general and on doing so more strongly in mlo5 plants may be mediated by the induction of oxidative stress.