Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/8/2007
Publication Date: 3/5/2007
Citation: Caniato, F., Guilamraes, C., Schaffert, R., Alves, V., Kochian, L.V., Borem, A., Klein, P., Magalhaes, J. 2007. Genetic Diversity for Aluminum Tolerance in Sorghum. Theoretical and Applied Genetics. 114(5):863-876. Interpretive Summary: Large areas of land within the U.S. and over 40% of the world’s arable lands are acidic. In these acid soils, aluminum (Al) toxicity is the primary factor limiting crop production via Al-induced inhibition of root growth. The physiological and molecular basis for Al tolerance is still poorly understood. Thus, we need a more complete understanding of the mechanisms underlying Al tolerance and the identity of the tolerance genes if we are going to be able to develop more Al tolerant crop plants for improved cultivation on acid soils. In this paper, we studied the genetic variation associated with a major Al tolerance gene we have named Alt-SB in the crop species, sorghum. In a survey of a broad range of sorghum lines, we found that this gene confers Al tolerance in most sorghum lines studied. However, in several of the lines, Al tolerance must be conferred by a novel and to date unidentified gene. A combined physiological and genetic analysis of the sorghum lines where Alt-SB confers Al tolerance showed that there are many variants for this gene. The significance of this work is that we have set the stage for improving sorghum Al tolerance via molecular-based breeding strategies that will allow plant breeders to introduce the most effective versions of this tolerance gene into sorghum breeding lines.
Technical Abstract: Significant genetic variation for aluminum (Al) tolerance in many plant species has allowed the development of cultivars that are high yielding on acidic, Al toxic soils. However, knowledge of intraspecific variation for Al tolerance control is needed in order to assess the potential for further Al tolerance improvement within crop species. In this study, we focused on the major sorghum Al tolerance gene, AltSB, from the highly Al tolerant standard SC283 to investigate the range of genetic diversity for Al tolerance control in sorghum accessions from diverse origins. Two tightly linked STS markers flanking AltSB were used to study the role of this locus in the segregation for Al tolerance in mapping populations derived from different sources of Al tolerance crossed with a common Al sensitive tester, BR012, as well as to isolate the allelic effects of AltSB in near-isogenic lines. The results indicated the existence not only of multiple alleles at the AltSB locus, which conditioned a wide range of tolerance levels, but also of novel sorghum Al tolerance genes. In addition, the presence of highly Al tolerant transgressive segregants indicates the breeding potential exists to exploit the additive or codominant effects of distinct Al tolerance loci. A global, SSR-based, genetic diversity analysis using a broader sorghum set revealed the presence of both multiple AltSB alleles and different Al tolerance genes within highly related accessions, suggesting that efforts toward broadening the genetic basis for Al tolerance in sorghum should not be solely based on genome-wide patterns of genetic diversity.