Identification of RFLP markers linked to the barley aluminum tolerance gene Alp

Aluminum (Al) toxicity limits crop productivity in acidic soils. As with many crops, natural genetic variation for Al tolerance has been found in barley (Hordeum vulgare L.). Al tolerance can be evaluated by replicated field trials, by soil bioassays in pots, or by solution culture methods. To date, alternative marker-assisted methods of Al tolerance selection in barley have not been developed. The goal of this study was to identify molecular markers for Alp, a gene in the barley cv Dayton that confers a high level of Al tolerance. An FZ mapping population was generated from a cross between Dayton and the more aluminum-sensitive cv Harlan Hybrid. Al tolerance in this population was scored by hematoxylin staining, and was confirmed to segregate in a monogenic fashion. Restriction fragment length polymorphism (RFLP) mapping of Alp was undertaken, and it was localized to the long arm of chromosome 4H, 2.1 cM proximal to the marker Xbcd1117 and 2.1 cM distal to the markers Xwg464 and Xcdo1395. These markers can be used for marker-assisted selection of Al tolerance in barley without the need for field trials, soil bioassays, or solution culture analysis. Further, the linkage between Xcdo1395 and Alp is interesting because this marker is also linked to the wheat (Triticum aestivum L.) Al tolerance gene Alb, located on the long arm of chromosome 4D. This result is suggestive of the possibility that Al tolerance in barley and wheat may be due to the action of orthologous loci.