Molecular mapping and mechanism of aluminium tolerance in five doubled haploid populations of Triticum aestivum L (bread wheat)

摘要

Aluminium (Al3*) toxicity is a serious constraint to wheat production on many acidic soils. To increase the selection efficiency of Al tolerance, identification of DNA markers diagnostic to Al tolerance can accelerate the development of cultivars tolerant to Al. Five DH populations derived from Diamondbird/Janz, Currawong/CD87, Spica/Maringa, Sunco/Tasman and Cranbrook/Halberd, were screened for Al tolerance by hematoxylin staining and/or by relative root growth measured at high Al concentrations insolution culture. The segregation ratios were consistent with expected ratio of 1:1 for one major gene controlling Al tolerance in these populations. The Al tolerance gene co-segregated with Al stimulated malate efflux (XALME) in the Diamondbird/Janz derived DH population. Linkage analysis showed that a major locus for Al tolerance maps on 4DL. Two SSRs; GDM125 and WMC48 were the closest markers linked with Al tolerance in these populations. Allele frequency of SSRs mapped within 20cM from locus associated with Al tolerance was investigated in 47 wheat genotypes collected mainly from Brazil to test the uniqueness of Al tolerance genes. The polymorphic information content values of SSRs varied from 0.31 to 0.83. All the 47 wheat genotypes ranked with respect to Al tolerance followed a similar pattern with malate efflux. Evidence that the Altl gene is involved in an Al stimulated excretion of malate was obtained from (i) co-segregation data on Al tolerance measured in solution culture and malate effluxin the Diamondbird/Janz DH population and (ii) a consistent correlation between malate efflux and level of tolerance in 47 genotypes of wheat. Mapping of Al tolerance on chromosome 4DL in wheat DH populations derived from the Diamondbird/Janz, Sunco/Tasman, and Cranbrook/Halberd confirm that Altl gene confers Al tolerance in these populations via a mechanism of malic acid secretion from roots.