Aluminum Tolerance in Forage Rye Breeding Lines.

Rye (Secale cereale L.) is important forage for livestock in east Texas, Oklahoma and other states throughout the southeast US. Combinations of high seedling vigor, high forage production and tolerance to Al³⁺ toxicity in acid soils make this species desirable as winter forage. A low pH (4.0) hydroponic solution with AlCl₃ added to specific levels was used for root elongation screening. A zero aluminum treatment was used to measure root growth in the absence of aluminum to calculate an aluminum tolerance index (ATI). Half-sib lines OV-RYE-12 were compared with the rye cultivar Elbon using an Elbon root growth ratio (ERG = [experimental line root growth in 4 mg Al/L] / [Elbon root growth in 4 mg Al/L]). Average root length was the average of the two longest roots on each plant. Number of observations (plants) for each line ranged from 55 to 60. The objective was to compare Al-tolerance in forage rye breeding lines (half-sib lines OV-RYE-12) by measuring root elongation responses in Al-containing hydroponic nutrient solutions. Actual root growth data allowed the identification of lines that had significantly more root growth (P < 0.05) compared to Elbon. The ATI data identified five lines (12-3, 12-9, 12-11, 12-7, and 12-5) equal to Elbon. Three of these lines (12-3, 12-9 and 12-11; P < 0.05) had enhanced root growth compared to Elbon. Forage rye root growth under Al³⁺ challenge conditions can help identify experimental germplasm with improved tolerance to Al³⁺ in acid soils.