The Journal of Heredity 1986:77(4):275-277
© 1986 The American Genetic Association 77:275-277
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A favorable linkage combination in the soybean
The author is research geneticist, USDA-ARS, P. O. Box 196, Stoneville, Mississippi 38776. He expresses appreciation to B. L. Keeling for providing cultures of the pathogen, to W. L. Barrentine for providing the herbicide, and R. L. Bernard and E. E. Hartwig for providing seed of the soybean parents used in the study. Joint contribution from USDA-ARS and the Mississippi Agricultural and Forestry Experiment Station, Stoneville, MS 38776.
Abstract
Very little information is available on linkage between desirable genes in the soybean [Glycine max (L.) Merr.]. The cultivars Douglas and Tracy-M carry different alleles for resistance to phytophthora rot (caused by Phytophthora megasperma Drechs. f. sp. glycinea Kuan and Erwin), and are tolerant to the widely used herblcide metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one]. If genes controlling these traits are linked, selection efficiency could be increased when cuitivars having these genes in coupling phase are used in crosses. The objective of this study was to verify this linkage and determine recombination frequencies. A soybean breeding line was used in reciprocal crosses with Douglas and Tracy-M. The F3 lines from these crosses were evaluated for reaction to hypocotyl inoculations with P. megasperma and to a 125µgL–1 concentration of metribuzin in a hydroponic system. Similar segregation ratios from reciprocal crosses indicated little or no cytoplasmic effects in reaction to either the pathogen or herbicide. The results indicate that the alleles Rpsl in Douglas and Rpsl-b in Tracy-M are closely linked with Hm, with recombination estimates of 5 percent and 6 percent, respectively.