ARS | Publication request: Distribution of Rht genes in winter wheat germplasm from the eastern and central United States

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 26, 2009
Publication Date: July 23, 2010
Citation: Guedira, M., Brown Guedira, G.L., Marshall, D.S., Van Sanford, D., Sneller, C., Souza, E.J. 2010. Distribution of Rht genes in winter wheat germplasm from the eastern and central United States. Crop Science. 50:1811-1822.

Interpretive Summary: The deployment of dwarfing genes in wheat was a key event in the development of the "Green Revolution" which led to significant increases in grain yields after the 1960s. The dwarfing genes resulted in plants having shorter, stiffer stems, thereby being better able to resist lodging. Over seventy percent of current wheat cultivars grown worldwide have a semi-dwarf phenotype controlled by the major genes Rht-B1 (formally Rht1), Rht-D1 (formally Rht2) from the Japanese variety ‘Norin10’ and Rht8 from the Korean variety ‘Akakomugi’. The objective of this study was to determine their frequency in a set of historic and modern soft and hard winter wheat cultivars grown in central and eastern United States. Three-hundred sixty-seven cultivars (250 soft winter wheat and 117 hard winter wheat) that were developed from 1808-2008 were evaluated with molecular markers for Rht-B1, Rht-D1 and Rht8. All cultivars released prior to 1960 had the tall version of all three genes. Among current soft winter wheat cultivars, the Rht-D1b dwarfing gene was the most frequent being present in 45% of all lines tested and the Rht-B1b gene was present in 27%. While in the hard winter wheat cultivars Rht-B1b allele is the most prevalent with 68% and only 7% of the cultivars tested had the Rht-D1b. No cultivar had both Rht-B1b and Rht-D1b. Analyses with the microsatellite marker Xgwm261 linked to the Rht8 locus indicated that this gene was less frequently used as a source of dwarfing in U.S. winter wheat germplasm, being present in 8 and 3 % of the soft winter wheat and the hard winter wheats, respectively. A number of cultivars were identified that did not have any of the dwarfing genes assayed and may possess alternate reduced height genes.

Technical Abstract: Over seventy percent of wheat cultivars grown worldwide have a semi-dwarf phenotype controlled by the major genes Rht-B1 (formally Rht1), Rht-D1 (formally Rht2) from the Japanese variety ‘Norin10’ and Rht8 from the Korean variety ‘Akakomugi’. The objective of this study was to determine their frequency in a set of historic and modern soft and hard winter wheat cultivars grown in central and eastern United States. Three-hundred sixty-seven cultivars (250 soft winter wheat and 117 hard winter wheat) that were developed from 1808-2008 were evaluated with molecular markers for Rht-B1, Rht-D1 and Rht8. All cultivars released prior to 1960 (41 soft winter wheat and 6 hard winter wheat) had wild-type (tall) alleles at all three loci. Among soft winter wheat cultivars, the Rht-D1b dwarfing gene was the most frequent being present in 45% of all lines tested and the Rht-B1b gene was present in 27%. While in the hard winter wheat cultivars Rht-B1b allele is the most prevalent with 68% and only 7% of the cultivars tested had the Rht-D1b. No cultivar had both Rht-B1b and Rht-D1b. Analyses with the microsatellite marker Xgwm261 linked to the Rht8 locus indicated that this gene was less frequently used as a source of dwarfing in U.S. winter wheat germplasm, being present in 8 and 3 % of the soft winter wheat and the hard winter wheats, respectively. A number of cultivars were identified that did not have any of the dwarfing genes assayed and may possess alternate reduced height genes.