Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 23, 1999
Publication Date: N/A
Interpretive Summary: Aluminum toxicity is a major factor that limits crop productivity on acidic soils of the U.S. and elsewhere on earth. In barley, the Alp gene improves the ability for this crop to grow on acidic soils. This study was undertaken to identify molecular markers linked to the Alp gene. Such markers may be used to efficiently select for increased aluminum tolerance in barley. The Alp gene was localized to the long arm of barley chromosom 4. Three RFLP markers were found to be tightly linked to Alp. By selecting for the presence of any of these markers, it is possible to predict the presence of the Alp gene with approximately 98% confidence, and thus these molecular markers will be of use to barley breeders who incorporate molecular breeding methods in their programs. One of the linked markers, cdo1395, is linked to a major aluminum tolerance gene in wheat as well. This result suggests that aluminum tolerance in wheat and barley may be conferred by different forms of the same gene. This result is significant because it suggests that if scientists can successfully clone the aluminum tolerance gene from wheat (which possesses more aluminum tolerance than barley), its transfer to barley is very likely to impart enhanced aluminum tolerance without the need for other molecular modifications.
Technical Abstract: Aluminum (Al) toxicity limits crop productivity in acidic soils. As with many crops, natural genetic variation for Al tolerance has been found in barley. Seedling solution culture screening methods for Al tolerance in barley have been used in lieu of field evaluations or soil bioassays, but still take several days to complete. The goal of this study was to identify molecular markers for Alp, a gene in the barley cultivar Dayton that confers a high level of Al tolerance. An F2 population was generated from a cross between Dayton and the aluminum-sensitive cultivar Harlan Hybrid. Al tolerance segregation was scored by hematoxylin staining, and was found to segregate as a single gene. RFLP mapping of Alp was undertaken, and this gene was localized to the long arm of chromosome 4, 2.1 cM proximal to bcd1117 and 2.1 cM distal to markers wg464 and cdo1395. The linkage between cdo1395 and Alp is interesting because this same marker ris linked to the wheat Al tolerance gene AltBH. The markers bcd1117, wg464, and cdo1395 can be used for indirect selection of Al tolerance in barley without the need for solution culture or replicated field trials. Additionally, our mapping data are suggestive of the possibility that in wheat and barley, intraspecific Al tolerance differences may in part be due to allelic variation at orthologous loci.