A Method for Detecting Genetic Variability for Grass Tetany Potential in Tall Fescue¹

Abstract

Seedlings of ‘Kentucky 31’ and open‐pollinated progeny from three genetically diverse tall fescue (Festuca arundinacea Schreb.) clones were screened for Mg and K concentrations at 2% and 21% rhizosphere 0 2 in sand cultures. Using six watertight and airtight boxes, 15 x 9 X 30 cm, filled with washed sand, 27 seedlings of each entry were grown in three replications at low (2%) and high (21%) rhizosphere 0 2 in the greenhouse. Magnesium uptake of tall fescue was reduced at low (2%) rhizosphere 0 2 . Seedlings grown at 2% 0 2 ranged from 0.13 to 0.36% Mg and from 1.4 to 3.3% K. Both Mg and K concentrations were lower at 2% 0 2 than at 21% 0 2 . Eight genotypes selected to represent a range in Mg and K levels at low 0 2 were grown past the seedling stage, vegetatively propagated into a soil culture, and evaluated for Mg and K at 2 and 21% rhizosphere 0 2 . A genotype selected for high Mg concentration at low 0 2 remained high in Mg at both low and high 0 2 in soil during a subsequent experiment. Low Mg genotypes remained low in Mg when grown in soil. All K levels were very high when older tissue was evaluated in soil. If plants with high Mg and low K can be identified and if the characteristic is heritable, tall fescue with low grass tetany potential could be developed.