Root rot resistance under forage and seed production systems

Red clover (Trifolium pretense L.) is an important forage legume grown in the USA, Canada, and northern and eastern Europe. The effects of root rot resistance of six improved cultivars and three regionally adapted ecotypes on forage and seed yield under typical production systems in Wisconsin and Oregon, respectively, were measured. The relationship of cultivar flowering capacity to seed yield was also measured. The objectives of this study were to: (i) determine the benefits of using improved cultivars instead of locally adapted ecotypes in Wisconsin forage production systems; (ii) determine whether selection for root rot resistance in Wisconsin benefits seed production systems in Oregon; and (iii) identify strategies to increase seed yields in cultivars with improved persistence and high forage yields. Forage and seed yields were inversely related in all improved cultivars except Kenland, which had lower forage yield than the other improved cultivars and the same yield as the three local Wisconsin and Oregon ecotypes. The local ecotypes produced the highest seed yield because of a greater flower producing capacity than improved cultivars following spring forage removal. Seed yield was highly associated with the number of flowers produced by late July (r = 0.87; P ≤ 0.002). Selection for root rot resistance in Wisconsin did not benefit seed production in Oregon. Improvement in seed yield capacity of cultivars with high forage yield may be possible by selecting for rapid flowering after spring forage removal in the western Oregon seed production region.