|Yue, B - NORTH DAKOTA STATE UNIV|
|Radi, S - DOW AGROSCIENCES|
|Cai, X - NORTH DAKOTA STATE UNIV|
|Tang, S - UNIV OF GEORGIA, ATHENS|
|Knapp, S - UNIV OF GEORGIA, ATHENS|
|Miller, J - RETIRED ARS|
Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 3, 2008
Publication Date: June 1, 2008
Citation: Yue, B., Radi, S.A., Vick, B.A., Cai, X., Tang, S., Knapp, S.J., Gulya, T.J., Miller, J.F., Hu, J. 2008. Identifying quantitative trait loci for resistance to Sclerotinia head rot in two USDA sunflower germplasms. Phytopathology. 98(8):926-931. Interpretive Summary: Sclerotinia head rot and stalk rot are the most important sunflower diseases in the northern Great Plains of the U.S. Since no reliable complete resistance germplasm is available, the breeding for Sclerotinia disease resistance has been relied on incorporating partial tolerance from different source. In order to dissect the genetic basis and to identify DNA markers associated with the genes contributing to head rot tolerance, we developed a mapping population from two USDA released lines with partial tolerance to head rot. We evaluated the mapping population for disease tolerance in three field experiments with a randomized complete block design with two replicates in two consecutive years. We constructed a linkage map with 180 TRAP markers, two morphological markers and 43 SSR and InDel markers. The SSR and InDel genotype data, collected by our collaborator, the Knapp Lab in the Center for Applied Genetic Technologies, The University of Georgia, Athens, GA enabled us to align the linkage groups with the public sunflower SSR marker map. We identified nine quantitative trait loci (QTL) for disease incidence and seven QTL for disease severity. One QTL was detected in all three experiments and four QTL were identified in two of the three experiments. The DNA markers mapped dear the QTL will be useful for marker-assisted selection in breeding for Sclerotinia resistance.
Technical Abstract: One hundred and twenty-three F2:3 and F2:4 families derived from a cross between HA 441 and RHA 439, both showing partial tolerance to Sclerotinia head rot, were used for the current study. A genetic map with180 TRAP, 32 SSR, 11 ZVG INDEL, and 2 morphological markers was constructed. The map has 19 linkage groups and spans a genetic distance of 1797.6 cM. The mapping population was evaluated for disease tolerance in three field experiments with a randomized complete block design with two replicates. Disease tolerance was assessed by disease incidence (DI) and disease severity (DS). Strong positive correlations were detected among the traits investigated in different tests. In total, nine and seven QTL were detected for DI and DS, respectively. These QTL, each with a LOD score ranging from 2.4 to 11.8, distributed on 10 of the 19 linkage groups. One QTL for DI was detected in all three experiments and two QTL for DI and DS, respectively, were identified in two of the three experiments. Identification and mapping of the tolerance QTL will facilitate marker-assisted selection of the disease tolerance in germplasm development and breeding. Although a positive correlation existed between the two disease indexes, most of the respective QTL were located in different chromosomal regions, suggesting a different genetic basis for the two indexes.