Main content area

Variability of Fraction 1 Protein and Heritability Estimates for Fraction 1 Protein and Total Phenolic Constituents in Alfalfa

Miltimore, J. E., McArthur, J. M., Goplen, B. P., Majak, W., Howarth, R. E.
Agronomy journal 1974 v.66 no.3 pp. 384-386
Medicago sativa nothosubsp. varia, alfalfa, bloat, breeding programs, clones, cultivars, heritability, ovens, pastures, phenolic compounds, protein content, soil fertility
The primary cause of lethal alfalfa pasture bloat is Fraction 1 Protein (FRIP) and bloat occurs when FRIP is above 1.8%. Before starting a selection or breeding program to develop a nonbloating alfalfa (Medicago sp.), it would be important to know the heritability and the range of FRIP levels in alfalfa plants. Accordingly, this investigation was undertaken with the objectives of determining the distribution of FRIP levels and the heritability of FRIP and total phenolic constituents in alfalfa clones. Sampling was undertaken at the prebud to bud stage of maturity. The top 15 cm of the plants were harvested. Fraction 1 Protein levels were obtained for 1,372 alfalfa plants of diverse origin. Only four plants, 0.3%, were below the bloat threshold of 1.8% in FRIP concentration on an oven dry weight basis. The average concentration for all alfalfa plants was 4.3%. M. sativa was generally higher in FRIP than other Medicago species. The lowest mean FRIP concentration, 3.1%, was found in M. hemicycla and M. glutinosa. A broad sense heritability estimate for FRIP was determined from a replicated nursery of 60 clones. With single plants from four replications in the first year, the heritability of FRIP was 28%. Heritability of total phenolic constituents in the first year using data from four replications was 16%. The correlation coefficient between years for FRIP was r = 0.40, 58 dr. Cultivar differences in FRIP, observed in the first year, disappeared the second year when soil fertility level was increased. The mean FRIP level in the second year was 4.8%.