Inheritance and linkage study of isozyme loci and morphological traits in red clover
Information on inheritance of isozymes and linkage maps in Trifolium pratense L is limited. Genetic analysis of 18 isozyme systems and three morphological traits (white vs. pink flower, present vs. absent leaf marker and green vs. sun-red stem) was conducted. Six loci of four isozymes had simple Mendelian inheritance. Joint segregation analyses among 8 isozyme loci and 3 morphological gene markers (55 pair-wise combinations) resulted in the assignment of one linkage group. Two morphological markers coding for flower (c) and stem (gs) color were found to be in the same linkage group based on the analyses of two segregating families. The recombination values of the two progenies for c-gs were 0.079 and 0.113. No linkage was found between any of the isozyme loci and the morphological traits.
Genetic Analysis of 11 Polymorphic Isozyme Loci in Chestnut Species and Characterization of Chestnut Cultivars by Multi-locus Allozyme Genotypes
Allozyme polymorphism in chestnut (Castanea) species was investigated using isoelectric focusing in thin-layer polyacrylamide slab gels. Genetic analysis of the progenies of intraspecific crosses and interspecific F 2 s and backcrosses (BC 1 s) allowed the verification of 11 polymorphic isozyme loci from 11 enzyme systems. The following loci were defined: Acp, Adh, Est-1, Est-2, Est-5, Me, Prx-1, Prx-2, Prx-3, Skd-3, and Skd-4. All polymorphic loci behaved as single-locus Mendelian genes. Skd showed unique species specificity. Skd-1 and Skd-2 were unique to the American chestnut (C. dentata Borkh.) and the European chestnut (C. sativa Mill.), whereas Skd-3 and Skd-4 were unique to the Chinese chestnut (C. mollissima Bl.) and the Japanese chestnut (C. crenata Sieb.). Linkage analysis revealed linkage for three pairs of loci: Skd- 3/Skd-4, Est-1/Est-2, and Est-5/Prx-1. The single-tree progeny method was used successfully for isozyme genetic analysis. Forty-seven chestnut cultivars in six chestnut species were characterized using 12 isozyme loci and can be unambiguously identified by 12 multi-locus genotypes. The interspecific and geographic relationships among species were also discussed.
Comparisons of Floral Response of Seed Lots of Dollard Red Clover, Trifolium pratense L. 1
The accumulated evidence (1, 2, 4, 5) suggests that one of the basic physiological differences between the two red clover types is that the medium varieties are capable of developing flowering stems without a period of exposure to near or sub-freezing temperatures. In contrast, the mammoth types apparently require exposure to low temperatures before floral stems will elongate and mature. Germ plasm of both types is being utilized in red clover breeding programs and varieties have been released that combine both types resulting in a varietal population with a diverse genetic base. Dollard red clover is an example of such a variety. Consequently, a diversity of plants ranging from completely rosette types to completely floral types can be found during the seedling year in the varietal populations. Bird (1) described five plant types based on the degree of floral stem development that can be found within the varietal population of Dollard during the seedling year. Smith (5) called attention to such plant type diversity as it may affect the maintenance of a variety through successive generations of increase. Steppler and Raymond (6) reported that a LaSalle seed lot, harvested from a seeding year stand, contained a higher percentage of floral-type plants than a seed lot harvested from the second year production of this seed field. They observed that plants producing seed during the seedling year usually failed to survive the following winter. Smith (5) working with Wisconsin common red clover also found a lower survival rate for the "flowering-types". Therrien and Smith (8) reported that the percentage of winter killing during the first winter was higher for the flowering plants than for the nonflowering plants of Dollard red clover. The question arises as to whether varietal populations derived from the combination of single-cut and double-cut germ plasm can be maintained through successive generations of seed increases. This question becomes more important when these increases are accomplished in vastly different environmental regimes such as those that prevail in the north central area of the U. S. where these varieties