Heterosis of forage quality in alfalfa

A semihybrid variety development system could capture natural hybrid vigor found between alfalfa (Medicago saliva L.) populations. Medicago saliva subsp. sativa and subsp.falcata represent a heterotic pattern that could be used in a semihybrid breeding system to increase yields, but the forage quality of inter-subspecific crosses in relation to intra-subspecific crosses is unclear. The objective of this study was to compare forage quality of sativa x falcata crosses (SFC), sativa x sativa crosses (SSC), and falcata x falcata crosses (FFC). We used the standard forage quality measures of in vitro dry matter digestibility (IVDMD), neutral detergent fiber (NDF), acid detergent fiber (ADF), acid detergent lignin (ADL), crude protein (CP), leaf/stem ratio (LSR), hemicellulose, and cellulose to measure stem forage quality of inter- and intra-subspecific sativa and falcata crosses. Forage was sampled in October 1998 and May 1999 at Ames, IA, and May 1999 Nashua, IA. Sativa-falcata hybrids had slightly decreased stem forage quality compared with the expected quality based on the average of the intra-subspecies cross means. For most forage quality traits the decreased quality is equivalent to the level of the poorer performing intra-subspecies parental mean.