The Relationship between Population Structure and Aluminum Tolerance in Cultivated Sorghum

Abstract

BackgroundAcid soils comprise up to 50% of the world's arable lands and in these areas aluminum (Al) toxicity impairs root growth, strongly limiting crop yield. Food security is thereby compromised in many developing countries located in tropical and subtropical regions worldwide. In sorghum, SbMATE, an Al-activated citrate transporter, underlies the AltSB locus on chromosome 3 and confers Al tolerance via Al-activated root citrate release.MethodologyPopulation structure was studied in 254 sorghum accessions representative of the diversity present in cultivated sorghums. Al tolerance was assessed as the degree of root growth inhibition in nutrient solution containing Al. A genetic analysis based on markers flanking AltSB and SbMATE expression was undertaken to assess a possible role for AltSB in Al tolerant accessions. In addition, the mode of gene action was estimated concerning the Al tolerance trait. Comparisons between models that include population structure were applied to assess the importance of each subpopulation to Al tolerance.Conclusion/SignificanceSix subpopulations were revealed featuring specific racial and geographic origins. Al tolerance was found to be rather rare and present primarily in guinea and to lesser extent in caudatum subpopulations. AltSB was found to play a role in Al tolerance in most of the Al tolerant accessions. A striking variation was observed in the mode of gene action for the Al tolerance trait, which ranged from almost complete recessivity to near complete dominance, with a higher frequency of partially recessive sources of Al tolerance. A possible interpretation of our results concerning the origin and evolution of Al tolerance in cultivated sorghum is discussed. This study demonstrates the importance of deeply exploring the crop diversity reservoir both for a comprehensive view of the dynamics underlying the distribution and function of Al tolerance genes and to design efficient molecular breeding strategies aimed at enhancing Al tolerance.

Duplicate and Conquer: Multiple Homologs ofPHOSPHORUS-STARVATION TOLERANCE1Enhance Phosphorus Acquisition and Sorghum Performance on Low-Phosphorus Soils

“…Supplemental Figure S2A reveals an evident change in DK with four subpopulations, indicating that this is a reasonable level of differentiation for the SAPst. As described previously, the pattern of genetic diversity in sorghum largely reflects racial and geographical origins (Casa et al, 2008;Caniato et al, 2011;Morris et al, 2013). The largest subpopulation, with 112 accessions, comprised mostly caudatum sorghums, followed by subpopulations with prevalence of durra, guinea/kafir, and breeding lines, with 93, 50, and 32 accessions, respectively.…”

Combining ability of grain sorghum lines selected for Aluminum tolerance

“…Populations derived from these three accessions indicated that Alt SB locus plays a role in controlling Al tolerance, although other minor genes in its background contribute to enhance tolerance (Magalhães et al 2004, Caniato et al 2007, Caniato et al 2011). All female lines share some similarity, once all of them were twice backcrossed to ATF54B.…”

Plant Adaptation to Acid Soils: The Molecular Basis for Crop Aluminum Resistance

“…This suggests that even in the case of major genes in crop species, allelic variation at auxiliary loci may give rise to polygenic inheritance of Al resistance in certain crosses. Although in-depth intraspecific investigations emphasized the importance of TaALMT1 and SbMATE in wheat and sorghum Al resistance, respectively (8,10,110), other important Al resistance genes may remain unidentified in those species. Perhaps the clearest case of monogenic inheritance of Al resistance is found in barley, where Al resistance in genotypes of distinct genetic origins has long been known to be due largely to an allelic series at the Alp locus, resulting in little potential for improvement beyond this locus (81).…”

“…High levels of Al resistance are rare in the sorghum germplasm, occurring at a frequency of approximately 5% (8). As such, breeding programs targeting sorghum adaptation to Al-toxic acid soils must rely on the deliberate identification and introduction of Al resistance donors.…”