Persistence and Yield Stability of Intersubspecific Alfalfa Hybrids

ABSTRACT Long‐term persistence and sustained biomass yields of alfalfa (Medicago sativa L.) stands are important to producers. Yield performance and persistence of intrasubspecific crosses between alfalfa subspecies sativa and falcata after the first post‐establishment year are unknown. The objectives of this study were to measure biomass yields, persistence, and biomass yield stability in inter‐ and intrasubspecific alfalfa crosses derived by mating nine elite sativa clones and five falcata clones in a half‐diallel. Progeny were space planted in 1998 at Ames and Nashua, IA, and evaluated for persistence, biomass yield, and biomass yield stability from 1998 through 2002. Medicago sativa subsp. sativa (sativa) × M. sativa subsp. falcata (falcata) hybrids produced substantial biomass yield and exhibited heterosis through the first post‐establishment year, but declined in subsequent years. From 1998 through 2002 the intersubspecific hybrids had persistence equivalent to the more persistent parental subspecies, with the effect becoming more apparent as time progressed. Intrasubspecific hybrids had less biomass yield stability than the more stable intrasubspecific sativa crosses. The results indicate that selection of improved falcata germplasm for long term persistence and higher yield is needed.