Variation of isoflavones production in red clover as related to environment, growth stage and year

Trifolium pratense cv. Minshan is a dominant red clover variety for animal feeding and pharmaceutical industry in Alpine Pasture Region of Gansu province, northwest China. In order to achieve the best isoflavone production, a 3-year trial was conducted at three locations to study variations of hay yield, total isoflavone concentration and isoflavone yield at different growth stages under different environmental conditions. Predominant isoflavone compounds and distribution of isoflavones in leaves, stems and inflorescences were also investigated. The results indicated that there were large variations on hay yield and isoflavone concentration among different sites, growth stages, age and parts of the plant. Minshan red clover harvested at the flower bud stage had the highest isoflavone yield (86.30 kg ha−1. The temperate climate region, Guanghe, provided the best growth conditions among three sites for isoflavone production (58.93 kg ha−1). The highest isoflavone production (53.42 kg ha−1) appeared at the second year of crop. In Minshan red clover, isoflavones are mainly distributed in leaves (1.12%). The predominant isoflavone compounds were formononetin (0.27%) and biochanin A (0.25%)