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item Devine, Thomas

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/2/2003
Publication Date: 11/1/2003
Citation: Devine, T.E. 2003. The Pd2 and Lf2 loci define soybean linkage group 16. Crop Science. 43:2028-2030.

Interpretive Summary: Genes are the entities that control inheritance. In plants, the genes are located in linear order along thread-like structures called chromosomes. The location of the genes on the chromosome determines whether they tend to be co-inherited (as when they are close together on the same chromosome) or inherited independently (as when the genes are far apart on the same chromosome or on different chromosomes). In this study I found that the lf2 gene, controlling the production soybean plants with leaves of seven leaflets rather than the usual 3 leaflets, was linked fairly close to another gene Pd controlling the production of a dense covering of plant hairs over the leaves and stems. The plant hairs are important in protecting soybean plants from damage by leafhopper insects. The lf2 gene may be important in regulating the amount of leaf material on the plant. When soybeans are used for forage the amount of leaf material has an important affect on the quality of the forage as livestock feed. When soybean breeders are attempting to couple or de-couple the lf2 and Pd genes in breeding new soybean cultivars knowing how these genes are linked will be helpful in estimating the numbers of progeny needed to achieve their goals.

Technical Abstract: The soybean genes lf2, controlling the production of leaves with seven leaflets, and Pd, controlling dense pubescence were tested for genetic linkage by analyzing the F3 generation from the hybridization of genetic stock line BV 20 with T264. BV 20 was homozygous for both the lf2 allele and the y17 allele and was selected from the F2 progeny of the cross T255, carrying the lf2 allele, and T162 carrying the y17 allele. T264 carried the Pd allele conditioning dense pubescence. The F1 and F3 seeds were produced in the field. The F2 generation was produced in the greenhouse. The F3 generation was classified for phenotype in the field at Beltsville, Maryland. Data was tested with chi-square for single-factor segregation and linkage. Estimates of recombination frequency were made using the method of maximum likelihood. The bisection method was used to solve the maximum likelihood equations. The linkage chi-square for the association of the lf2 locus and the pd locus was very high, indicating linkage of these loci. The recombination frequency between the lf2 and pd loci was estimated at 12%. The linkage of the lf2 and pd loci is designated classical linkage group 22. Soybean breeders attempting to couple or de-couple the lf2 and Pd alleles in their breeding populations should take cognizance of this linkage association in estimating the population sizes required to achieve their goals.