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United States Department of Agriculture

Agricultural Research Service

Title: SSR MARKERS EXHIBIT TRISOMIC SEGREGATION DISTORTION IN SOYBEAN [GLYCINE MAX (L.) MERR.]

Authors
item Zou, J. - UNIVERISTY OF ILLINOIS
item Singh, R. - UNIVERSITY OF ILLINOIS
item Lee, J. - UNIVERSITY OF ILLINOIS
item Xu, Steven
item Hymowitz, T. - UNIVERSITY OF ILLINOIS

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 20, 2006
Publication Date: May 18, 2006
Citation: Zou, J.J., Singh, R.J., Lee, J., Xu, S.S., Hymowitz, T. 2006. SSR markers exhibit trisomic segregation distortion in soybean. Crop Science. 46:1456-1461.

Interpretive Summary: A normal individual in a species is known as a disomic while an individual with a normal chromosome complement plus an extra complete chromosome is known as a primary trisomic. Primary trisomic is a useful tool to assign an individual gene and a group of genes (linkage group) to specific chromosomes in plant species. In cultivated soybean, eleven molecular linkage groups (MLG) were previously assigned to their respective chromosomes using molecular markers and primary trisomics based on altered segregation ratios from a disomic (1:2:1) to a trisomic genotypic ratio (6:11:1) in the offspring derived from the crosses of soybean primary trisomics and a wild soybean progenitor species Glycine soja. In this study, we further established the association between chromosome 4 and MLG C1 based on standard trisomic segregation ratio (6:11:1). In addition, we observed that four molecular markers on chromosome 4, 13, and 17, respectively, segregated in a 1:11:6 ratio, which is the reverse of the standard trisomic ratio. This is the first report of trisomic segregation distortion in soybean. The cultivated soybean G. max and its progenitor species G. soja usually differ either by a reciprocal translocation or by a large inversion. Their hybrids usually undergo some structural changes in chromosomes such as deletion and duplication, which can cause abortion or preferential fertilization of specific gamete genotypes, thus causing distorted segregation ratios. In addition, structural changes in a chromosome may be more likely for trisomic chromosomes than those in the normal disomic state. Therefore, we hypothesize that the genomic divergence between the two species and the numerically unbalanced genome in the trisomics might contribute to the distorted trisomic ratios. Our results indicate both normal and distorted trisomic segregation ratios should be considered when analyzing the association between chromosomes and linkage groups using primary trisomic analysis.

Technical Abstract: A primary trisomic (2n = 2x + 1) is an excellent cytogenetic tool to locate genes and associate linkage groups to their respective chromosomes in diploid plant species. In soybean [Glycine max (L.) Merr.], eleven molecular linkage groups (MLGs) were previously assigned to their respective chromosomes using simple sequence repeat (SSR) markers and primary trisomics. The chromosome location of the SSR markers was determined by altered segregation ratios from a disomic (1:2:1) to a trisomic genotypic ratio (6:11:1) in the F2 offspring derived from the crosses of soybean primary trisomics and G. soja. In this study, we established the association between soybean Triplo 4 and MLG C1 based on trisomic segregation ratio (6:11:1) and cytological analysis. In addition, we identified four SSR markers that exhibited trisomic segregation distortion on three soybean chromosomes. Those SSR markers, including Satt565 and SOYGPATR on chromosome 4 (MLG C1), Satt193 and Satt226 on chromosomes 13 (MLG F) and 17 (MLG D2), respectively, segregated in a 1:11:6 ratio, which is the reverse of the standard trisomic genotypic ratio. This is the first report of trisomic segregation distortion in soybean. Since G. max and G. soja usually differ either by a reciprocal translocation or by a paracentric inversion, we hypothesize that the genomic divergence between the two species and the numerically unbalanced genome in the trisomics might contribute to the distorted trisomic ratios. Genome instability may have been triggered in F1 primary trisomics, causing unexpected trisomic inheritance in F2. Our results indicate both normal and distorted trisomic segregation ratios should be considered when analyzing the association between chromosomes and linkage groups using primary trisomic analysis.

Last Modified: 10/31/2014
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