Two Cycles of Directional Selection for Improved Nutritive Value of Alfalfa
1970
Shenk, John S. | Elliott, Fred C.
A 6-hour in vitro dry matter disappearance (GH-DMD) procedure was used to evaluate individual progeny of ‘Vernal’ (Medicago sativa L. and Medicago falcata L.) and ‘DuPuits’ (Medicago sativa 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, Medicago glutinosa 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.
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