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Recurrent Selection for Seedling Vigor in Birdsfoot Trefoil¹

In 1969, a program of recurrent selection for seedling vigor in ‘Leo’ birdsfoot trefoil (Lotus corniculatus L.) was initiated. Seed for all tests was garnered from openpollination nurseries, small-seeded lines were discarded, and seedling vigor tests were conducted indoors on the remainder. In each cycle the most vigorous seedlings from the most vigorous lines were selected to be the parents of the next cycle. Three cycles were completed. In 1972, nursery material representing cycles 0, 1, 2, and 3 was established and harvested for seed.

Three types of experiments were used to evaluate progress: 1) random seed samples from each cycle were bulked within cycles to provide four treatments, including the check; 2) pedigree test—18 lines from each cycle, randomly chosen from within seed weight classes, were tested; and 3) a series of routine tests were used primarily to identify superior lines. In these routine tests only lines that were at least average in seed size were included.

In the bulk test the percentage improvement in seedling vigor for cycles 1, 2, and 3 over the cydc 0, or Leo population, was 10, 34, and 40%, respectively. For the pedigree test it was 20, 36, and 36%. For four routine tests the average improvement was 30, 47, and 52%. The average improvement in seed size was 36%. Inbreeding and a relaxation of selection pressure were considered responsible for the lack of progress in cycle 3 compared to cycle 2.

Possible uses of seedling vigor tests to provide information on breeding methods are discussed.

Key Words: Lotus corniculatus • Seed size improvement • Breeding methods

² Associate Professor, University of Guelph, Guelph, Ontario, Canada.

Received for publication July 3, 1973.

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