Aluminum (Al) toxicity in acid soils significantly affects plant growth, agricultural productivity and ecosystem health. Here we investigated plant Al tolerance from evolutionary physiological, molecular, and ecological perspectives. Genetic similarity and phylogenetic analysis of Al tolerance-associated gene families showed that many of these were conserved from streptophyte algae to angiosperms, indicating land plants have evolved gradually in adaptation to Al-rich acid soil during plant terrestrialization. In particular, vacuolar phosphate transporter SPX-major facility superfamily (SPX-MFS) and inorganic phosphate (Pi) transporter 1 subfamily (PHT1s) of streptophyte algae showed higher genetic similarity to land plants than chlorophyte algae. PHT1 subfamily exhibited a significant expand during the evolution from streptophyte algae to liverworts and then to eudicots. Moreover, we identified an Al-tolerant Tibetan wild barley accession XZ29, showing high levels of Phosphorus(P)-containing glycolytic intermediates under Al stress. We found a new Al-tolerance mechanism that Al-induced Pi efflux from root elongation zone to chelate rhizosphere Al3+ and immobilization of Al with P reduce Al accumulation in barley root cells. These results indicated that Tibetan wild barley has evolved unique P transport and metabolism for the adaptation to harsh conditions in eastern and southeastern Tibet where acid soils contain high P.

In-crop soil waterlogging caused by extreme rainfall events, high ground water tables, excessive irrigation and lateral ground water flow inhibit potential grain yields. However, the extent to which yield is influenced by the timing and duration of waterlogging relative to crop phenology is unknown. To investigate this, we conducted various waterlogging treatments on a range of modern barley genotypes varying in their waterlogging tolerance, with tolerance conferred through aerenchyma formation under oxygen deficit conditions. Results showed that yield was reduced by 35% in W1 (waterlogging at Zadoks stage (ZS) 12.5 for one month) to 52% in WL3 (waterlogging at ZS 15 for two months) due to fewer spikes/m2 and kernels/spike. Two weeks waterlogging at ear emergency stage had the greatest impact on yield (70% reduction) due to its effect on spikelet fertility and grain filling. Phenology was delayed 1-8 ZS at the end of waterlogging treatments, with the waterlogging-susceptible cultivar Franklin showing the greatest delays, and waterlogging tolerant genotypes capable of AF (Macquarie+, TAMF169) having the least delays (0-4 ZS). Genotypes with the AF QTL (Macquarie+) showed a slight and nonsignificant yield reduction compared with unwaterlogged controls and mitigated around 23% yield loss under early phenological waterlogging stress.