Two cycles of directional selection for improved nutritive value of alfalfa.

A 6-hour dry matter disappearance (GH-DMD) procedure was used to evaluate individual progeny of ‘Vernal’ (L. and L.) and ‘DuPuits’ (L.) clones selected for high or low 6H-DMD values. Progeny derived from clones with high GH-DMD values had consistently higher 6H-DMD values than progeny from low clones. Additional clones of ‘Culver’ MSA-C4, MSB-C4, M.B., and Vernal were screened for high or low 6H-DMD values over two harvests. Selected clones from Vernal and DuPuits progeny and from the five unselected populations were recombined for a second cycle of directional selection.Correlations between yield and 6H-DMD were negative or near zero. Cell wall analysis of clones selected for a second cycle of improvement indicated a significant positive relationship between total cell wall constituents (NDF) and 6H-DMD values of the forage.Second cycle clones had significant general and specific combining abilities for yield as well as leaf and NDF content. Progeny from clones with high GH-DMD values were higher in leaf content but lower in NDF content than progeny from clones with low GH-DMD values. Comparisons of selected two-clone combinations in the first and second cycles indicated second cycle selection was effective in separating progeny means.