Premium
Effect on Fertility at the Tetraploid Level of the Genome Derived from Diploid Medicago falcata 1
Author(s) -
Oldemeyer Robert K.,
Brink R. A.
Publication year - 1953
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1953.00021962004500120004x
Subject(s) - citation , ploidy , medicago , biology , fertility , library science , genealogy , demography , history , genetics , sociology , population , computer science , gene
THE present study is concerned with the effect on fertility at the tetraploid (2;z = 32 chromosomes) level of genomes derived from diploid (2n = 16 chromosomes) Medicago fdlcata. The relationship has been examined in three classes of individuals: (1) artificially induced autotetraploid M. falcata, (2) F1 and F2 hybrids between these autotetraploids and ordinary tetraploid plants from Cossack, a commercial variety of alfalfa, and (3) such Fx hybrids backcrossed once to the respective parental forms. Interest in the problem rests on the likelihood that the diploid forms of M. falcata constitute a reservoir of genes more or less distinct from that which has been drawn upon in the formation of the prevailing cultivated varieties. The alfalfas grown in northern regions are derived mostly, if not exclusively, from hybrids between M. saliva and M. falcata. They are tetraploid, and comprise a highly diverse assemblage of plant types to which the name M. media is often applied. The two parental species are now known to be represented by-both tetraploid and diploid forms (1, 3, .10). Diploid M. saliva is rare, and diploid M. falcata is uncommon, although rather widespread in Europe and Asia, judging from the infrequency with which these forms have been encountered among the many wild alfalfas introduced into the United States and Canada. The common occurrence over a wide area in Europe and Asia of tetraploid M. falcata is presumptive evidence that it is this form, rather than the diploid, which has entered into the cultivated varieties of M. media. The barriers to effective hybridization engendered by the difference in ploidy would be expected to restrict severely the amount of gene exchange between 16-chromosome and 32-chromosome forms; hence the expectation that the diploid M. falcata gene pool contains unique elements. There is a limited amount of direct evidence that diploid M. falcata is the repository of economically important germplasm. The results (unpublished) of recent comparative tests in Wisconsin, for example, show that the vari-