Aluminum tolerance in triticale, wheat, and rye

Acid soils containing high levels of aluminum (Al) are known to severely limit plant growth on over 1.6 billion hectares worldwide. In the United States, a gradual decline in the pH of many soils both in the Great Plains as well as the Southeast, has caused many soils to become high in levels of free Al. This worldwide condition encouraged the analysis of wheat (Triticum aestivum L. em Thell.), triticale (X Triticosecale Wittmack), and rye (Secale cereale L.) germplasm from one of the major acid soil regions of the world (Brazil) in order to evaluate and compare the genetic potential of Al genes for cereal improvement. The objectives were to compare Al-tolerance levels in wheats, triticales, and ryes by measuring root elongation responses in Al-containing hydroponic nutrient solutions. Root elongation was impaired for all species grown in 1 mg/L concentrations of Al. Rye had the longest root regrowth and Al-sensitive wheats had the shortest root regrowth. The triticales containing a 2D(2R) substitution developed in the mid-1970s had the poorest root regrowth of all triticale types. The newly developed advanced triticale lines (AABBRR) yet to be released for commercial production showed the highest degree of Al tolerance of all the triticale types and approached or exceeded the levels observed in rye. This indicated that progress is being made in improving Al-tolerance of triticale in Brazil. Of all the old and new wheat varieties showing the highest degree of Al-tolerance, none of them were better than ‘BH 1146’ a variety that is at least 50 years old. This indicated that over the past 50 years, although Brazilian wheat breeders have made yield improvements in wheat production, they have not improved Al-tolerance. Rye showed a higher degree of Al-tolerance than the other cereals when tested in 1 mg/L of Al, but as expected, some variation was noted.