Factors affecting isoflavone concentration in red clover ( Trifolium pratense L.)

Red clover (Trifolium pratense L.) contains isoflavones, which are of interest because of their benefits for human health as well as their adverse effects on the fertility of farm animals. Isoflavone concentration in 10 cultivars ranged from 8923 to 12753 μg g-1 DM averaged across sites, harvests, and years. One cultivar, 'Start', distinguished itself with particularly low isoflavone levels. Concentrations varied according to plant part with leaves having the highest levels followed by stems and inflorescences, when averaged across maturity levels and cultivars (11970, 4896 and 3297 μg g-1 DM, respectively). Greatest content was found in leaves and stems during vegetative stages. Fresh herbage contained higher isoflavone content than either silage or hay (14464, 12200 and 11604 μg g-1 DM, respectively). Foliar application of yeast extract, chitosan, and acetic acid elicitors overall showed modest (12-15%) increases in isoflavone concentration over untreated control plants. Differences were not observed between elicitor concentrations used.