Diverse origins of aluminum-resistance sources in wheat.

Aluminum (Al) toxicity is a major constraint for wheat production in acidic soils. Wheat producers now routinely use Al-resistant cultivars as one cost-effective means to reduce risks associated with acidic soils. To date, diverse Al-resistant materials have been identified, but their genetic relationship has not been well characterized. A total of 57 wheat accessions, including the majority of the parents of Al-resistant accessions we identified in a previous study, were evaluated for Al resistance and analyzed with 49 simple sequence repeat (SSR) markers and 4 markers for Al-activated malate transporter (ALMT1). Pedigree and principle coordinate analysis (PCA) both separated Al-resistant accessions into four groups labeled according to common ancestry or geographical origin: US-Fultz, Polyssu, Mexican and Chinese. Al resistance in the four groups may have three independent origins given their distinct geographic origins and gene pools. Fultz originated in the USA as a major ancestor to soft red winter wheat, Polyssu originated in Brazil as a major source of Al resistance used in most genetic studies worldwide, and the Chinese group originated in China. Based on ALMT1 marker haplotypes, the Al resistance in the Polyssu and Mexico groups was likely derived from Polyssu, while most Al-resistant cultivars developed in the USA most likely inherited most of Al resistance from Fultz. Fultz was released about 50 years earlier than Polyssu. Norin 10 likely played a pivotal role in passing Al-resistant gene(s) from Fultz to better adapted, semi-dwarf wheat cultivars developed in the USA. Further characterization of Al resistance in the three different sources could reveal multiple Al-resistant mechanisms in wheat.