Location: Forage Seed and Cereal Research UnitTitle: A method to select for root chelation activity in annual ryegrass
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 10/3/2019
Publication Date: N/A
Technical Abstract: Acidic soils reduce plant nutrient availability, increase toxic cations - particularly aluminum (Al3+), and can occur in areas where grasses are grown for seed, forage, or cover crops. Grasses tolerant to acidic soils produce root exudates with higher concentrations of chemicals that chelate Al3+ than sensitive plants. The objective of this research was to develop a high-throughput assay to measure root exudate chelation capacity (CC) to facilitate breeding grasses tolerant to acidic soils. The color indicator dye Chrome azurol S (CAS) is bound to metal ions, and the loss of these ions due to chelation by a test chemical causes decreased absorption at 595 nm. Chelation capacity is calculated as absorbance of test samples divided by absorbance of a rooting solution. An optimized assay using the copper form of CAS with 2.0 mM CaCl2 in 10 mM MES buffer (pH under 5.5) with or without addition of Al3+ as AlCl2 (30.0 µm) gave rapid and consistent results. Seeds of annual ryegrass cultivar Gulf were germinated in 48 tissue cluster wells (1 seed/well) with 300 µl rooting solution. Rooting solutions sampled from the wells with germinating seedling were tested for chelation capacity in plate reader, and ranged from 0.3 to 1.0. Seedlings were grown into three-tiller plants, retested for CC, and measurements were correlated to the seedling assay (r=0.43, P=0.04). Plants were divided into low (CC>0.78) and high (CC<0.5) chelation groups of nine plants each and allowed to intermate. Mean CC of progeny seedlings from low (0.93) and high (0.78) groups were significantly different (t=2.6, P<0.01). These results indicate that this colorimetric assay is valuable for determining ryegrass root exudate chelating activities and that CC appears to be a heritable trait.