Genetic Variability for Chemical Composition of Alfalfa. I. Mineral Elements1

A series of four‐parent diallel crosses was constructed with patents randomly selected from ‘Saranac’ alfalfa (Medicago sativa L.). The single crosses and parents were evaluated in small field plots during each of 2 harvest years to determine genetic variability for mineral concentration. Quantitative genetic analyses were conducted for concentrations of phosphorus, potassium, calcium, magnesium, manganese, iron, copper, boron, aluminum, zinc, sodium, and Ca/P in first‐harvest forage. Significant additive genetic variance was observed for all traits, except Cu, Al, Zn, and Na concentrations. Except for digenic genetic variance for Cu concentration, nonadditive genetic variances were not significant. At the soil fertility levels of our experiment, clones from Saranac alfalfa contained less P, Cu, Zn, and Na, more K and Ca, and a higher Ca/P ratio than recommended for a moderately producing dairy cow. Deviations from the recommended levels of the remaining elements were minor and considered unimportant. Estimated potential ranges of mineral concentrations that could be achieved through plant breeding showed that i) the P‐deficiency could be corrected, ii) correction of the Zndeficiency and the excessive Ca/P ratio would be possible, but difficult, and iii) deviations from dairy cow requirements for Cu, Na, K, and Ca could not be corrected through plant breeding without alteration of soil fertility levels. Genotypic correlations were significant for the following pairs of traits: P and K, P and Fe, K and Fe, Ca and Mg, Ca and Fe, Ca and the Ca/P ratio, and Mg and Fe. All these genotypic correlations were positive.