Within- and among-cultivar genetic variation in alfalfa: Forage quality, morphology, and yield

Alfalfa (Medicago sativa L.) cultivars are synthetic populations formed fro m 8 to 200 parents and thus have a broad genetic base. Within-cultivar vari ation was compared with among-cultivar variation for energy value traits, m orphological traits, and dry matter yield. Eleven cultivars, each represent ed by 15 clones of 7 to 20 genotypes, were evaluated in field plots simulat ing a dense canopy at INRA (National Institute of Agronomic Research), Lusi gnan in France. Six harvests spanning 3 yr were analyzed. Neutral detergent fiber (NDF), acid detergent fiber (ADF), acid detergent lignin (ADL), enzy matic digestibility, leaf-to-stem ratio (LSR), number of stems, stem height , and dry matter yield were measured. Within-cultivar variance accounted fo r 31 to 70% of the genetic variance for LSR and quality traits and 57 to 10 0% for morphological traits and dry matter yield. Large within-cultivar var iation for yield-related traits could impart yield stability across environ ments, as a result of competition in alfalfa canopies. Phenotypic and genet ic correlations were relatively low in each harvest for dry matter yield an d NDF content, but high for NDF content and LSR. Within-cultivar variation could be exploited as an additional source of genetic variation in breeding programs for quality traits to achieve a higher genetic gain per breeding cycle.