Genetic characterization of aluminum tolerance in winter wheat

Aluminum toxicity in acidic soils is a major constraint to winter wheat productivity in the southern Great Plains, USA. In this study, a population of recombinant inbred lines generated from a cross between two winter wheat cultivars, ‘Jagger’ with high acidic soil tolerance and ‘2174’ with moderate acidic soil tolerance, was used to map genes for acidic soil tolerance in the field. As expected, a major QTL centered on TaALMT1 on chromosome 4DL was observed. Further sequencing, however, indicated that Jagger carried an allele having Type V of triplicated sequence repeats in TaALMT1-1, whereas 2174 carried an allele having Type IV of two (A–B) block sequences in TaALMT1-2. The Jagger TaALMT1-1-V allele was expressed at a significantly higher level than the 2174 TaALMT1-2-IV allele not only in roots as reported in previous studies but also in leaves found in this study. No sequence was found for genes to be homoeologous to TaALMT1 in any of the recently released genomic sequences of diploid, tetraploid, or hexaploid wheat, suggesting that neither TaALMT1-A nor TaALMT1-B exists in wheat. Therefore, TaALMT1 is a gene unique to genome D. In addition, Jagger had the favorable allele at a QTL mapped on chromosome 2DL, whereas 2174 had the favorable allele at a QTL mapped on chromosome 7BL. The combination of these three complementary QTLs/genes/alleles may help to generate winter wheat lines that confer greater tolerance to acidic soils.