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United States Department of Agriculture

Agricultural Research Service

Research Project: IMPROVEMENT OF HARD RED SPRING AND DURUM WHEAT FOR DISEASE RESISTANCE AND QUALITY USING GENETICS AND GENOMICS Title: Comparative analysis of genetic background in eight near-isogenic wheat lines with different H genes conferring resistance to Hessian fly

Authors
item Xu, Steven
item Chu, C -
item Harris, M -
item Williams, Christie

Submitted to: Genome
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 25, 2010
Publication Date: December 25, 2010
Citation: Xu, S.S., Chu, C.G., Harris, M., Williams, C.E. 2010. Comparative analysis of genetic background in eight near-isogenic wheat lines with different H genes conferring resistance to Hessian fly. Genome. 54:81–89.

Interpretive Summary: Lines that are genetically identical, except for one gene, are referred to as near-isogenic lines (NILs). Near-isogenic lines are useful tools for investigating gene expression and for detecting molecular markers closely linked to the genes. However, the use of NILs for genetic and genomic analysis relies on the homogeneity of the genetic background. A set of eight NILs (Carol, Erin, Flynn, Iris, Joy, Karen, Lola, and Molly) were previously developed by individually transferring the Hessian fly-resistance genes (H3, H5, H6, H9, H10, H11, H12, and H13) into winter wheat cultivar ‘Newton’ through backcross. However, genetic similarity among the eight NILs, Newton, and the donor parents of the genes has not been investigated. In this study, we performed comparative genetic analysis among NILs, Newton and the corresponding Hessian fly-resistance gene (H gene) donors. Based on a total of 256 molecular markers, the genetic similarity among NILs, Newton, and the H gene donors were calculated and used for the comparison. The results showed that five of the NILs, including Carol (H3), Erin (H5), Flynn (H6), Iris (H9) and Molly (H13), had a highly uniform genetic background of Newton, and Karen (H11) had slightly increased genetic difference from Newton. Joy (H10) and Lola (H12) had much increased genetic difference from Newton, suggesting that they should not be treated as NILs until they are improved by additional backcrosses. This study indicated that the genetic similarity between each of the NILs and Newton was affected by both the number of backcrosses and the genetic similarity between Newton and the H gene donors. The study suggested that the genetic residues of the donor parents that remained in the NILs were not due to the drag along of the genes that were transferred. Results from this research provide useful information for developing and using near-isogenic lines in genetic and genomic studies of wheat.

Technical Abstract: Near-isogenic lines (NILs) are useful tools for investigating gene expression, detecting closely linked markers, or cloning the genes. However, the reliability of using NILs for genetic and genomic analysis relies on the homogeneity of the genetic background. In this study, a set of eight NILs (Carol, Erin, Flynn, Iris, Joy, Karen, Lola, and Molly) that were previously developed by individually transferring the Hessian fly-resistance genes (H3, H5, H6, H9, H10, H11, H12, and H13) into winter wheat ‘Newton’ through backcrossing, were genotyped using the TRAP (target region amplification polymorphism) marker system. Comparative genetic analysis was then conducted among NILs, Newton, and the corresponding Hessian fly-resistance gene (H gene) donors. Based on a total of 256 TRAP polymorphic markers generated, the genetic similarity (Nei and Li’s coefficient) among NILs, Newton, and the H gene donors were calculated and used for comparison. The results showed that five NILs, including Carol (H3), Erin (H5), Flynn (H6), Iris (H9) and Molly (H13), had a highly uniform genetic background of Newton, and Karen (H11) had slightly increased divergence from Newton. Joy (H10) and Lola (H12) showed much increased divergence from Newton, suggesting that they should not be treated as NILs until they are improved by additional backcrosses. Cluster analysis based on similarity coefficients and pedigree analysis indicated that the genetic similarity between each of the NILs and Newton was affected by both the number of backcrosses and the genetic similarity between Newton and the H gene donors. By using a whole set of Chinese Spring nulli-tetrasomics, we were able to assign about one third of the TRAP markers that showed polymorphism between NILs and Newton to a specific chromosome. All assigned markers were located in chromosomes other than the one carrying the corresponding H gene, suggesting that the genetic residues of the donor parents that remained in the NILs were not due to linkage drag. Results from this research provide useful information for developing and using near-isogenic lines in genetic and genomic studies of wheat.

Last Modified: 11/27/2014