W1 Locus Research Articles

Genetic linkage of the Adh1 and W1 loci in soybeans

Four crosses were made among seven soybean cultivars for determining possible linkage between Adh1 and W1 loci. An examination of F2 seed indicated that these loci are linked with a recombination value of 20.6 ± 1.2%. These loci are located in linkage group 8. Key words: soybean linkage, isozymes, alcohol dehydrogenase (Adh1), color locus (W1), Glycine max.

Genetic study of glutamate oxaloacetic transaminase in soybean

A four-band electrophoretic zymogram for glutamate oxaloacetic transaminase (GOT, EC 2.6.1.1) is observed in mature soybean (Glycine max (L.) Merr.) seed. The zymogram pattern has a cluster of three bands (Rf's of 0.26, 0.29, and 0.32) and a single band. No variation was observed in the cluster of three bands. The fourth band has three variants that are controlled by a single locus, Got, with three alleles. They are designated as Got-a (Rf = 0.52), Got-b (Rf = 0.54), and Got-c (Rf = 0.57), respectively. In the wild soybean, G. soja (Sieb. & Zucc), the Got-a allele was found in four accessions from South Korea (PI 407.194, PI 407.269, PI 407.270, and PI 504.286; frequency 4/187). The Got-c allele also was found in four G. soja accessions from South Korea (PI 407.184, PI 407.207, PI 407.222, and PI 407.225; frequency 4/187). All other G. soja accessions examined carry the Got-b allele (frequency 179/187). All the G. max cultivars and accessions examined are homozygous for the Got-b allele (frequency 320/321) except for cv. Hardee, in which two seeds were homozygous for the Got-c allele. Linkage tests show that the Got locus segregates independently of the Ap, Dia1, Dia2, Idh1, Pgd2, and W1 loci. No linkage was detected when isozyme loci other than Got were tested (Am3–W1, Ap–W1, Dia1–W1, Pgd–W1, Dia1–Idh1, Pgd2–Idh1, and Ap–Idh2). Key words: soybean, glutamate oxaloacetic transaminase, GOT, electrophoresis, isozymes.

Locating the w1 Locus on the Satellite Chromosome in Soybean1

F2 data of field‐grown plants of a cross between translocation 172‐11‐3 (purple flower, W1) and type collection line T93A (white flower, w1) of soybean [Glycine max (L.) Merr.] revealed a significant deviation from the expected ratio of 3 purple: 1 white. To determine the cause(s) of the abnormal ratio, the chromosome number and constitution of the F2 progenies of another cross involving 172‐11‐3 and T161 (white flower) were determined. Translocation 172‐11‐3 has cytologically recognizable interchange chromosomes, and the short interchange chromosome was present as a univalent in 46% of the pollen mother cells (PMCs) in interchange heterozygotes. Sixty‐five percent of the F2 progeny were disomics of the N/N, N/T, and T/T types, 18% were trisomics, 16% were 40‐chromosome plants with a duplication‐deficiency gamete, and 1% were 42‐chromosome plants. Assuming that the univalent was lost in the cytoplasm 50% of the time, the observed number of N/N and N/T plants fit the expected, but the number of T/T did not. A recombination frequency of 1.9% between w1 and the breakpoint was calculated. The F2 data of duplex trisomic hybrids indicated that the w1 locus was on the satellite chromosome. The breakpoint on the long arm of the satellite chromosome is distal to the w1 locus. Our data indicated no linkage between the breakpoint and the genes y10 (chlorophyll deficiency) and t (pubescence color).

Analysis of genetic linkage in the soybean

Genetic linkage was established between the Rj1 locus, controlling restricted nodulation, and the F locus, controlling fasciated stem in the soybean (Glycine max (L.) Merr.). A distance of 40 ± 2.2 genetic map units was determined to separate these two loci. This is the first report of genetic linkage of a locus controlling nodulation in the higher plants. The Rj1 locus was determined to be Independent of the P locus in linkage group 2, the Ln locus in linkage group 4, the L1 locus in linkage group 5, the W1 locus in linkage group 8, and the Rps1 locus in linkage group 10. Rj1 was found to assort independently of Fr1 Fr2 Lf2 and Y3; Rj2 was independent of Fr1 and L1; Rj4 was independent of L1 Fr1 and Y9; P was independent of Fr1 Ln, and Y9 and Y9 was independent of Ln.