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United States Department of Agriculture

Agricultural Research Service

Research Project: EVALUATION AND IMPROVEMENT OF CEREAL GERMPLASM FOR DISEASE RESISTANCE AND WINTER-HARDINESS

Location: Plant Science Research

Title: Population Structure, Linkage Disequilibrium, and Genetic Diversity in Soft Winter Wheat Enriched for Fusarium Head Blight Resistance

Authors
item Benson, J -
item BROWN-GUEDIRA, GINA
item Murphy, J -
item Sneller, C -

Submitted to: The Plant Genome
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 11, 2012
Publication Date: July 10, 2012
Citation: Benson, J., Brown Guedira, G.L., Murphy, J.P., Sneller, C. 2012. Population Structure, Linkage Disequilibrium, and Genetic Diversity in Soft Winter Wheat Enriched for Fusarium Head Blight Resistance. The Plant Genome. 5:71-80.

Interpretive Summary: Fusarium head blight (FHB), or head scab, is an economically important disease of wheat. The occurrence of epidemics of Fusarium head blight in U.S. winter wheat during the past two decades has resulted in increased emphasis on development of resistant cultivars. Understanding the effect of focused breeding efforts for FHB resistance on the genetic diversity and population structure in soft winter wheat germplasm in the eastern United States is important for mapping resistance genes and conducting DNA marker-assisted breeding. A set of 251 lines selected from three collaborative FHB screening nurseries was genotyped with DNA markers to assess genetic diversity and relationships. Although the lines evaluated were targeted to distinct production zones (northern vs. southern) of the eastern winter wheat region, cluster and principal component analyses did not detect separation of lines into sub-populations. The lack of major sub-groups in these germplasm may be the result of a short, intense breeding history for scab resistance and wide-spread use of common resistant parents. Our data indicated that sharing of germplasm among U.S. winter wheat programs focused on development of FHB resistant cultivars is common.

Technical Abstract: The occurrence of epidemics of Fusarium head blight (FHB), caused by Fusarium graminearum Schwabe, in U.S. winter wheat (Triticum aestivum L.) during the past two decades has resulted in increased emphasis on development of resistant cultivars. Understanding the effect of focused breeding efforts for FHB resistance on the genetic diversity, population structure (PS) and linkage disequilibrium (LD) in soft winter wheat germplasm in the eastern United States is important for marker-assisted breeding and use of association analysis to map resistance QTL. A set of 251 lines selected from three collaborative FHB screening nurseries was genotyped with SSR, STS and DArT markers to assess genetic diversity, PS, and LD,. The genome–wide average of LD decay to r2 < 0.2 was 9.9 cM and moderate levels of LD (r2 >0.2) were generally constrained to markers less than 5 cM apart. Although the lines evaluated were targeted to distinct production zones (northern vs. southern) of the eastern winter wheat region, cluster and principal component analyses did not detect separation of lines into sub-populations. The lack of major sub-groups in these germplasm may be the result of a short, intense breeding history for scab resistance and wide-spread use of common resistant parents. Our data indicated that admixture and sharing of germplasm among U.S. winter wheat programs focused on development of FHB resistant cultivars is common.

Last Modified: 9/10/2014