Submitted to: Plant Cell Tissue And Organ Culture
Publication Type: Review Article
Publication Acceptance Date: April 23, 2003
Publication Date: December 1, 2003
Citation: Samac, D.A., Tesfaye, M. 2003. Plant improvement for tolerance to aluminum in acid soils. A review. Plant Cell Tissue And Organ Culture. 75(3):189-207. Technical Abstract: Development of acid soils that limit crop production is an increasing problem world-wide. Many factors contribute to phytotoxicity of these soils, however, in mineral acid soils, aluminum (Al) is the major cause of toxicity. The target of Al toxicity is the root tip, in which Al exposure causes inhibition of cell elongation and cell division, leading to root stunting accompanied by reduced water and nutrient uptake. Natural variation for Al tolerance has been identified in many crop species and in some cases tolerance to Al has been introduced into productive, well-adapted varieties. Aluminum tolerance appears to be a complex multigenic trait. Selection methodology remains a limiting factor in variety development as all methods have specific drawbacks. Molecular markers have been associated with Al tolerance genes or quantitative trait loci in several crops, which should facilitate development of additional tolerant varieties. A variety of genes have been identified that are induced or repressed upon Al exposure. Most induced genes characterized so far are not specific to Al exposure but are also induced by other stress conditions. Ectopic overexpression of some of these genes has resulted in enhanced Al tolerance. Additionally, expression of genes involved in organic acid synthesis has resulted in enhanced production of organic acids and an associated increase in Al tolerance. This review presents the three main approaches that have been taken to develop crops with Al tolerance: recurrent selection and breeding, development of Al tolerant somaclonal variants, and ectopic expression of transgenes to reduce Al uptake or limit damage to cells by Al.