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Bloat Investigations: Determination of Soluble Protein Concentration in Alfalfa

Howarth, R. E., McArthur, J. M., Goplen, B. P.
Crop science 1973 v.13 no.6 pp. 677-680
plant physiology, plant biochemistry, field crops
A rapid, reliable method for the determination of soluble protein concentration in alfalfa was developed for use in studies on the bloat potential of alfalfa (Medicago sativa L.) and in breeding a low bloat-causing alfalfa cultivar. A two-step extraction procedure was used to obtain a crude aqueous extract. The colorimetric, biuret method for protein determination was modified by taking absorbance readings at two wavelengths (550 and 708 nm) to correct for interference by colored substances in the alfalfa extract. By this method the soluble protein concentration in fresh alfalfa was 50 to 70% of crude protein concentration. The correlation (r = 0.36) between soluble and crude protein was low (p > 0.05). The coefficient variation for soluble protein concentration was 10.5% in a population of 289 plants of diverse genetic origin, indicating the possibility of selecting for low soluble protein concentration as a means of developing a low bloatcausing alfalfa cultivar.