|Guedira, Mohammed -|
|Benson, Jared -|
Submitted to: Eastern Wheat Workers and Southern Small Grain Workers Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: May 20, 2009
Publication Date: N/A
Technical Abstract: A set of 260 historic and modern eastern winter wheat cultivars were evaluated with the markers for Rht-B1, Rht-D1 and Rht8 dwarfing genes. The Rht-D1b dwarfing gene was the most frequent being present in 45% of all lines tested. The Rht-B1b gene was present in 28% of lines and the remaining lines were determined to have neither of the GA-insensitive genes. No cultivars had both Rht-B1b and Rht-D1b. All but one cultivar released prior to 1970 had tall alleles at all three loci. Although 25% of cultivars with release dates between 1970 and 1989 had neither Rht-B1b nor Rht-D1b, only eight of 153 releases after 1990 were not semi-dwarfs. The Rht-D1b dwarfing gene is more common in the eastern SWW region than Rht-B1b and was observed in 61% of the tested cultivars released after 1970. Analysis of the 2008 Uniform Eastern and Southern Soft Winter Wheat Nurseries along with the Soft White Winter Wheat Nursery indicates that although Rht-D1b was present in 73% of all entries, its frequency varied by nursery. Results indicate that the semi-dwarf habit in breeding programs in the Northeast and Southeast is predominantly due to Rht-D1b, while mid-western programs have a higher frequency of Rht-B1b. Only 20 of the 260 cultivars tested had the 192 base pair allele for Xgwm261 indicative of the Rht8 gene. Eighteen of the twenty lines presumed to have Rht8 also have the mutation for photoperiod insensitivity at the Ppd-D1 locus linked to Rht8. The observed association with Ppd-D1, along with pedigree information of early introductions, supports the conclusion that Rht8 is present in eastern soft winter wheat germplasm, albeit at a low frequency.