Introgressed TaMATE1B gene enhances grain yield and drought tolerance in durum wheat grown in Al3+-rich acidic subsoils

Subsoil acidity with a high aluminium (Al3+) content inhibits root growth and proliferation of durum wheat (tetraploid AABB, Triticum turgidum) leading to poor nutrient and water uptake. The TaMATE1B and TaALMT1 genes, encoding citrate and malate transporters, respectively, chelate Al3+ to render it non-toxic and thus enhanced Al3+ tolerance. This study evaluated the introgressed TaMATE1B gene on drought resistance and Al3+ toxicity in durum wheat. Durum wheat lines Jandaroi–TaMATE1B (introgressed with the TaMATE1B gene) and Jandaroi–null (without TaMATE1B gene) were grown in rhizoboxes (Expt. 1) and columns (Expt. 2) both filled with re-constructed field soil with Al3+-rich acid subsoil in a glasshouse under well-watered conditions until maturity (Expt. 1), or until the onset of ear emergence (Z51), before imposing well-watered and terminal drought treatments (Expt. 2). In Expt. 1, introgression of the Al3+-tolerant TaMATE1B allele into durum wheat enabled root growth and proliferation below 0.25 m of the soil profile, where the soil pH was low (4.1, CaCl2 extract) with high Al3+ content (16.5 mg kg−1), and increased total root length and biomass at 42 days after sowing (DAS; Z33) by 38.3 and 22%, respectively, relative to the Jandaroi–null. Differences in root growth between the two lines were apparent from tillering stage (Z33) and by 50% anthesis (Z64), respectively. Jandaroi–TaMATE1B had 69.2% greater root biomass, 76.2% greater root length, and 18% greater shoot biomass than Jandaroi–null at 50% anthesis (Z64). In Expt. 2, Jandaroi–TaMATE1B produced 25.3% higher grain yield than Jandaroi–null under well-watered conditions and 49.0% higher grain yield under terminal drought. Terminal drought reduced grain yield by 47.7% in Jandaroi–TaMATE1B and 72% in Jandaroi–null, relative to well-watered conditions. The effects of TaMATE1B on grain yield can be attributed to increased root growth and proliferation below 0.4 m in Al3+-toxic soil. Jandaroi–TaMATE1B had 34.5% and 32.0% more total root biomass than Jandaroi–null in the well-watered and terminal drought treatments, respectively. To conclude, introgression of the Al3+-tolerant TaMATE1B gene into durum wheat enabled root growth and proliferation down an acidic soil profile with a high Al3+ concentration, and improved terminal drought resistance by enabling root growth and proliferation into deep layers of Al3+-rich acidic soil. Separated studies under controlled environments and initial field trials in three different sites provide supportive evidence that the TaMATE1B and TaALMT1 genes can be used to enhance the Al3+ tolerance and drought resistance of commercial durum germplasm with improved production on acid soils.