Variety Synthesis in Alfalfa
1974
Lowe, C. C. | Cleveland, R. W. | Hill, R. R.
We compared performance of conventional synthetics, double-cross synthetics, and the parental components of the double-cross synthetics in a series of field experiments of alfalfa (Medicago sativa L.). Nine clones that had been selected for high general combinging ability were used as parents for the nine 4-clone combinations studied. Synthetics were produced by several methods of synthesis. The forage yield of the synthetics, measured in broadcast-seeded trials at three locations in New York and Pennsylvania, was used to compare the methods of synthesis. All seeds were produced in cage isolations in California and New York. Honeybees (Apis mellifera L.) were used as pollinators. Conventional 4-clone synthetics consistently yielded slightly more than the double-cross synthetics. True double-cross hybrid varieties from these parents would probably yield about 104% of that of the double.cross synthetics or about equal to the conventional synthetics. Advanced generations of 2-clone synthetics (components of double.cross synthetics) were consistently lower yidlding than any 4-clone synthetic which had the same two clones in its parentage. This agrees with theoretical expectations on inbreeding. Permutations of parent clones in synthesis of double-cross synthetics affected performance but no permutation exceeded the corresponding conventional synthetic. Double-cross synthetics made from Syn 2 generations of 2-clone synthetics as parent lines yielded the same as those made from the Syn 1 generations of the parent lines. Differences observed in performance of synthetics produced in California and New York were attributed to differences in methods of establishing the plantings in seed production cages.
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