Aluminum tolerance of wheat cultivars and relation to arbuscular mycorrhizal colonization in a non-limed and limed Andisol

Wheat (Triticum aestivum L.) cultivars vary extensively in their response to acidic soils. In southern Chile, wheat genotypes have been selected for growth on acidic Andisols where high concentrations of phytotoxic aluminum (Al) limit plant growth. Previous work indicates that arbuscular mycorrhizal (AM) fungi play an important role protecting plant roots against the deleterious effects of Al. To understand interactions between AM fungi and cultivar Al phytotoxicity, six locally used wheat cultivars ('Bakan', 'Crac', 'Invento', 'Maxi', 'Otto', and 'Porfiado') were cultivated in a non-limed and limed Andisol (74 and 5% Al saturation, respectively). Plant harvests were carried out at two phonological stages: tillering (60 days after sowing, DAS) and physiological maturity (150 DAS). Plant growth was limited on non-limed soil, but varied by cultivar. Among the cultivars, 'Porfiado' and 'Crac' exhibited growth traits consistently associated with acidic soil resistance, including greater biomass and root length and higher P/Al and Ca/Al ratios in plants grown in non-limed soil. Wheat growth was positively correlated with AM colonized root length and Al bound to glomalin related soil protein (Al-GRSP). In addition, root Al concentration was negatively correlated with colonized root length and Al-GRSP across all wheat cultivars grown under high Al saturation. The significantly better performance of wheat cultivars and their association with AM fungal traits on non-limed soils indicates that indigenous AM fungal populations in acidic soils may contribute to Al tolerance of some wheat cultivars when growing at high Al levels.