Attempted compensation for linkage drag affecting agronomic characteristics of durum wheat 1AS/1DL translocation lines

Authors: Klindworth, Daryl; Hareland, Gary; ELIAS, ELIAS - North Dakota State University; Xu, Steven

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2012
Publication Date: 2/6/2013
Citation: Klindworth, D.L., Hareland, G.A., Elias, E.M., Xu, S.S. 2013. Attempted compensation for linkage drag affecting agronomic characteristics of durum wheat 1AS/1DL translocation lines. Crop Science. 53:422-429.

Interpretive Summary: When incorporating a desirable gene from a wild-wheat relative to cultivated wheat, undesirable genes that are linked, or attached, to the desirable gene are introduced into the cultivated wheat. These undesirable genes usually reduce crop yield or quality, and this is referred to as linkage drag. In this experiment, we attempted to measure and reduce linkage drag associated with a segment of chromosome 1D from bread wheat incorporated into durum wheat. A durum wheat having the chromosome 1D segment was backcrossed to six durum cultivars, Renville, Ben, Lebsock, Maier, Rugby6, and Rugby68. After completing six backcross cycles, plants having (T-lines) or lacking (N-lines) the chromosome 1D segment were selected from each population. After producing sufficient seed of each line, field studies were conducted. We found that N-lines did not differ from their parental cultivars for any traits, suggesting that the backcrossing had successfully incorporated the genetic background of the cultivars into the new lines. We also found that compared to lines from an earlier study, most T-lines did not have improved yield. Grain yield of those lines was 11.1 to 20.5% less than their parental cultivars. However, the Lebsock T-lines had significant yield improvement, though still yielded 8.2% less than Lebsock. A significant reduction of thousand kernel weight was present in T-lines, and this was similar to the lines from an earlier study. We concluded that removal of linkage drag associated with the chromosome 1D segment will be dependent upon improving thousand kernel weight, and this may require further reducing the size of the 1D segment.

Technical Abstract: Yield reduction due to linkage drag caused by introgression of alien chromatin is a major problem for incorporating new genes into durum wheat (Triticum turgidum L. subsp. durum). Here we report attempts to improve yield of 1AS•1AL-1DL translocation lines of durum wheat that had previously been reported to have reduced yield due to linkage drag. Near-isogenic lines (NILs) were produced by six backcrosses of a translocation stock to five cultivars, Renville, Rugby, Lebsock, Ben, and Maier. During backcrossing, we found that ‘Rugby’ had two glutenin biotypes, with one biotype having high molecular weight (HMW) subunits 1Bx6+1By8 (Rugby68), and the second biotype having only 1Bx6 (Rugby6). Rugby6 and Rugby68 did not significantly differ for any trait other than HMW subunits. Rugby6 and Rugby68 were each used to develop a set of NILs. Translocation (T-lines) and non-translocation (N-lines) NILs were yield tested at five North Dakota locations. N-lines did not significantly differ from their parental cultivars for yield, heading date, height, protein content, test weight, or thousand kernel weight (TKW). The Lebsock T-lines yielded significantly less (8.2%) than Lebsock, but yielded significantly better than their parental T-lines. None of the other T-lines had significant yield improvement. All T-lines had from 5.9 to 11.3% reduction in TKW. The results indicate that genetic background is very important in reducing linkage drag. We conclude that improved yield of the 1AS•1AL-1DL translocation lines will be dependent on improving TKW, and this may be best accomplished by further reducing the size of the alien segment.