ARS | Publication request: Identification of Chromosome Locations of Genes Affecting pre-Harvest Sprouting and Seed Dormancy using Chromosome Substitution Lines in Tetraploid Wheat (Triticum turgidum L.)

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 27, 2009
Publication Date: July 1, 2010
Citation: Chao, S., Xu, S.S., Elias, E., Faris, J.D., Sorrells, M. 2010. Identification of Chromosome Locations of Genes Affecting pre-Harvest Sprouting and Seed Dormancy using Chromosome Substitution Lines in Tetraploid Wheat (Triticum turgidum L.). Crop Science. 50:1180-1187

Interpretive Summary: Pre-harvesting sprouting (PHS) refers to germination of grain in the ear prior to harvesting under high moisture field conditions. PHS damage often leads to a reduction in both grain yield and grain quality. Seed dormancy, the main factor contributing to PHS resistance, is a complex trait and strongly influenced by environmental growth conditions. To better understand the genetic control of PHS and seed dormancy, 37 genotypes were grown in nine field environments and evaluated for seed dormancy and PHS resistance in this study. Seed dormancy was assessed based on seed germination rate in a seven-day period. PHS was evaluated by subjecting spikes to simulated rainfall in a mist chamber for four days. PHS scores were determined by visually rating the extent of sprouting. The 37 genotypes used in this study were derived from three sets of single chromosome substitution lines in a durum wheat (Triticum turgidum var. durum) cultivar, Langdon, background with each of the 14 Langdon chromosomes substituted with its counterpart originating from three wild emmer (T. turgidum var. dicoccoides) accessions. Single chromosome substitution lines allow the traits affected by genes on single chromosomes to be studied in a homogeneous background. Consequently they are useful for dissecting the inheritance of complex traits, such as PHS. Wild emmer, a close relative of cultivated durum wheat, is known to be a rich source of genetic variation including novel genes for disease resistance and end-use grain quality that can be used for genetic improvement of cultivated wheat. The substitution lines involving chromosome 3A, which harbors a gene for red kernel color, were among the most dormant genotypes, which was consistent with the previous findings of close association of red seed color with higher levels of dormancy and PHS resistance. Germination tests further indicated that five additional chromosomes contained genes influencing seed dormancy at a level comparable to chromosome 3A. Results from PHS tests indicated that PHS was affected by at least eight wild emmer chromosomes including 3A. The chromosomes harboring genes for seed dormancy did not fully correspond with those for PHS resistance. The weak correlations between PHS and dormancy observed in this study indicate that different genes are affecting these traits and they may be differentially influenced by the environment. Nonetheless, our results revealed that genes present on five chromosomes, 2A, 2B, 3A, 4A and 7B, were found to affect both PHS resistance and seed dormancy. These genotypes, thus, provide useful resources for further studies on genetic interactions that contribute to the overall phenotypic variation, and on genetic dissection of genes underlying PHS resistance.

Technical Abstract: Seed dormancy, the main factor contributing to pre-harvest sprouting (PHS) resistance, is a complex trait and strongly influenced by environmental growth conditions. In this study, three sets of single chromosome substitution lines, including 37 genotypes, in a durum wheat (Triticum turgidum var. durum) background with donor chromosomes originating from three wild emmer (T. turgidum var. dicoccoides) accessions were grown in nine field environments and evaluated for seed dormancy and PHS resistance. The substitution lines involving chromosome 3A, which harbors a gene for red kernel color, were among the most dormant genotypes. Germination tests indicated that five additional chromosomes contained genes influencing seed dormancy at a level comparable to chromosome 3A. Results from PHS tests indicated that PHS was affected by at least eight T. dicoccoides chromosomes including 3A. The chromosomes harboring genes for seed dormancy did not fully correspond with those for PHS resistance. The weak correlations between PHS and dormancy observed in this study indicate that different genes are affecting these traits and they may be differentially influenced by the environment. Nonetheless, our results revealed that genes present on five chromosomes, 2A, 2B, 3A, 4A and 7B, were found to affect both PHS resistance and seed dormancy. These genotypes, thus, provide useful resources for further studies on genetic interactions that contribute to the overall phenotypic variation, and on genetic dissection of QTLs underlying PHS resistance.