HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Pfeiffer, T. W. Articles by Bingham, E. T. Search for Related Content PubMed Articles by Pfeiffer, T. W. Articles by Bingham, E. T. Agricola Articles by Pfeiffer, T. W. Articles by Bingham, E. T.

Improvement of Fertility and Herbage Yield by Selection within Two-Allele Populations of Tetraploid Alfalfa¹

Two tetraploid alfalfa (Medicago sativa L.) clones were obtained by chromosome doubling two cultivated diploid clones. The doubled plants were selfed and progeny from within each group were sibbed for four generations to develop two populations of tetraploid alfalfa, HG2 and W315, with a maximum of two alleles per locus. Selection was based upon winter survival and differential fertility in the self and first two sib generations. In the third and fourth sib generations visual selection for vigor was practiced. Inbreeding increased from F = 0.33 to F = 0.54. Crosses between the two populations, and with two different male sterile testers, were made with the initial doubled plants and the second and fourth sib generations. Crosses between the advanced generations of the two populations yielded significantly more forage in progeny yield tests than the cross of the initial doubled plants. For the HG2 population progeny from crosses to male sterile testers by the advanced generations yielded significantly more than progeny from similar test crosses using the initial parent. An increase in cross fertility with advancing generations occurred in the same population. Forage yields of clonal rows were two to three fold greater for the fourth sib generation than for the initial doubled plant in the HG2 population. Changes in the W315 population over generations were small and variable but occurred while the level of inbreeding was increasing in the population. Allelic heterozygosity could not increase in these populations. No new dominant alleles were added to mask unfavorable recessives in a linkage block. Assuming that interlocus interactions are absent, improvement must have come from the accumulation of favorable alleles already present due to recombination within linkage blocks.

Key Words: Medicago sativa L. • Sibbing • Chromosome doubling • Heterozygosity • Linkage • Linkats

² Formerly graduate research assistant (now assistant professor, Dep. of Agronomy, Univ. of Kentucky, Lexington, KY 40546) and professor, respectively, Dep. of Agronomy, Univ. of Wisconsin, Madison, WI 53706.

Received for publication November 22, 1982.