Bacterial wilt caused by Xanthomonas translucens pv. graminis (Xtg) is a major disease of Italian ryegrass (L. multiflorum Lam.). Although targeted resistance breeding has resulted in cultivars with considerable levels of resistance, the mechanisms of inheritance of resistance are poorly understood and further breeding progress is difficult to obtain. In this study, molecular genetic diagnostic tools were used to characterize pathogen populations und to investigate the genetic control of resistance. Molecular genetic characterization of 30 Xtg isolates revealed only moderate genetic diversity when compared to other pathogens. In addition, there was only moderate variation in virulence among the isolates while distinct differences in susceptibility among three L. multiflorum cultivars were observed. QTL analysis based on a high density linkage map and artificial inoculation in the field and in the glasshouse revealed one major QTL which explained up to 70 % of the resistance. In addition, several additional QTLs were identified which explained a smaller proportion of the resistance observed. The genomic regions identified in this study form a first basis for marker assisted improvement of bacterial wilt resistance in L. multiflorum.
Stucky T., Hochstrasser M., Meyer S., Segessemann T., Ruthes A. C., Ahrens C. H., Dahlin P., Pelludat C.
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