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One hundred random clones from 'Cherokee' alfalfa (Mediccigo sativa L.) were evaluated by self-(S,), topcross-, and clonal-progeny tests. Clonal progenies were most effective, topcross progenies moderately effective, and S, progenies the least effective in predicting first-cross yield. Forage yield was mostly independent of self-fertility. Nine clones were selected for yielding ability based on the progeny tests. The nine clones, their S, families, the diallel set of single-cross families from the nine clones, and the Syn 1 and Syn 2 generations of 10 synthetic varieties from the nine clones were evaluated. The best single-cross family yielded 150 7c; the best Syn 1 yielded 132 % ; and the best Syn 2 yielded 116% of 'Cherokee'. The predicted yield of the best synthetic possible among the nine clones in the equilibrium generation (Syn 4 and beyond) was 109 'I( of 'Cherokee'. The Syn 2 yields were predicted with 94 % , 91 % , and 851/o accuracy (as measured by regression analysis) from formulas based on diallel-cross yields, general-combining-ability yields, and clonal yields, respectively, coupled with S, family yields and coefficients of inbreeding. The coefficients of inbreeding alone could account for more than 80 % of the variation among Syn 2 varieties. The negative effect of inbreeding and gene recombination on advanced generations was apparent. Only a few of the 502 synthetic varieties possible from the 9 selected clones were predicted to outyield 'Cherokee' in the equilibrium generation. The prediction formulas will allow one to determine with reason-able accuracy (1) the number of clones to include in a synthetic variety, (2) the parents that are likely to produce the best possible variety, and (3) the quantity that the variety will yield in the generation the farmer plants. KEY WORDS: breeding, breeding Medicago sativa L., heterosis, inbreeding depression, Medicago sativa L., plant breeding.

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