Herbage Yields and Levels of N and IVDDM from Five Alfalfa Strains of Different Ploidy Levels
1978
Arbi, Nitza | Smith, Dale | Bingham, E. T. | Soberalske, R. M.
Cultivated alfalfa (Medicago sativa L.) cultivars are primarily tetraplolds, and data are sparse about the performance of alfalfa strains of different ploidy levels. Related diploid, tetraploid, and hexaploid alfalfa strains and a ‘Vernal’ check were compared in seeded row plots at Madison, Wisconsin. The soil was a fertile Dodge silt loam (Typic Hapludalf). The alfalfas were harvested during 2 years with two, three, or four cuts annually,, and the forage was analyzed for concentrations of nitrogen and in vitro digestible dry matter (IVDDM). Herbage, N, and IVDDM yields averaged over alfalfa strains were similar for two and three cuts annually, and were lowest for four cuts. Percentages of N and IVDDMw ere in the increasing order of two, three, and four cuts annually and similar for all ploidy levels within a cutting schedule. The 4x strains produced higher yields of herbage, N, and IVDDM than the 2x and 6x strains within each cutting schedule. The 2x strain outyielded the 6x strain with two cuts annually, but the reverse was the case with three and four cuts annually. This same response of strains was apparent in the residual herbage yields, within each cutting schedule, which were in the descending order of two, three, and four cuts annually. It was concluded that among the materials tested the tetraploid level had the highest yield potential and that the experimental diploid was best suited to a two-cutting schedule. The tetraploid that was synthesized to maximize heterozygosity [4x (70-44)] outyielded the check cultivar ‘Vernal’ at all cutting frequencies. Lack of maximum heterozygosity in the hexaploid was a possible reason for its comparatively poor performance.
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