Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 5, 2006
Publication Date: March 4, 2006
Citation: Chu, C.-G, Faris, J.D., Friesen, T.L., Xu, S.S. 2006. Molecular mapping of hybrid necrosis genes Ne1 and Ne2 in hexaploid wheat using microsatellite markers. Theoretical and Applied Genetics. 112:1374-1381. Interpretive Summary: Hybrid necrosis, characterized by gradual pre-mature death of leaves or plants on the hybrids between lines of hexaploid common wheat, is a serious barrier either for combining desirable traits from different lines of common wheat or for transferring genes from related species to commercial cultivars. A series of classical studies previously revealed that this phenomenon is genetically controlled by two complementary dominant genes Ne1 and Ne2 located on the long arm of chromosome 5B and the short arm of 2B, respectively. To date, molecular markers linked to these necrosis genes have not been identified. We observed that the hybrids from the crosses between the bread wheat variety ‘Alsen’ and four synthetic hexaploid wheat (SHW) lines (TA4152-19, TA4152-37, TA4152-44, and TA4152-60) developed at the International Maize and Wheat Improvement Center (CIMMYT) exhibited hybrid necrosis. This study was conducted to determine which necrosis genes (Ne1 and Ne2) that the SHW lines and Alsen carry and to map the genes using molecular markers. Genetic analysis indicated that Alsen carries Ne2 whereas the SHW lines carry Ne1. Two molecular markers were found to be closely linked with Ne1 and Ne2, respectively. Thus, relatively precise locations of the two necrosis genes in the genetic maps of wheat have been determined. The closely linked molecular markers identified in this study can be used to evaluate wheat lines for presence of Ne1 and Ne2 or to eliminate the two hybrid necrosis genes using marker-assisted selection.
Technical Abstract: Hybrid necrosis is the gradual pre-mature death of leaves or plants in certain F1 hybrids of wheat (Triticum aestivum L.), and it is caused by the interaction of two dominant complementary genes Ne1 and Ne2 located on chromosome arms 5BL and 2BS, respectively. To date, molecular markers linked to these genes have not been identified and linkage relationships of the two genes with other important genes in wheat have not been established. We observed that the F1 hybrids from the crosses between the bread wheat variety ‘Alsen’ and four synthetic hexaploid wheat (SHW) lines (TA4152-19, TA4152-37, TA4152-44, and TA4152-60) developed at the International Maize and Wheat Improvement Center (CIMMYT) exhibited hybrid necrosis. This study was conducted to determine the genotypes of TA4152-60 and Alsen at the Ne1 and Ne2 loci, and to map the genes using microsatellite markers in backcross populations. Genetic analysis indicated that Alsen has the genotype ne1ne1Ne2Ne2 whereas the SHW lines have Ne1Ne1ne2ne2. The microsatellite marker Xbarc74 was linked to Ne1 at a genetic distance of 2.0 cM on chromosome arm 5BL, and Xbarc55 was 3.3 cM from Ne2 on 2BS. Comparison of the genetic maps with the chromosome deletion-based physical maps indicated that Ne1 lies in the proximal half of 5BL, whereas Ne2 is in the distal half of 2BS. Genetic linkage analysis showed that Ne1 was about 35 cM proximal to Tsn1, a locus conferring sensitivity to the host selective toxin Ptr ToxA produced by the tan spot fungus. The closely linked microsatellite markers identified in this study can be used to genotype parental lines for Ne1 and Ne2 or to eliminate the two hybrid necrosis genes using marker-assisted selection.