|Campbell, Benjamin - Todd|
Submitted to: Czech Journal of Genetics and Plant Breeding
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2010
Publication Date: 10/1/2011
Citation: Baenziger, P.S., Dweikat, I., Gill, K., Eskridge, K., Berke, T., Shah, M., Campbell, B.T., Ali, M.L., Mengistu, N., Mahmood, A., Auvuchanon, A., Yen, Y., Rustgi, S., Moreno-Sevilla, B., Mujeeb-Kazi, A., Morris, M.R. 2011. Understanding grain yield: It is a journey, not a destination. Czech Journal of Genetics and Plant Breeding. 47:S77-S84. Interpretive Summary: Understanding the genetic architecture of grain yield could lead to significant advances in wheat productivity. Approximately 20 years ago, we began our efforts to understand grain yield in winter wheat using unique genetic strains and populations. Initially, we identified two chromosomes (3A and 6A) that contain genes responsible for 15 to 20% grain yield increases. The genes on chromosomes 3A and 6A responsible for higher yield were mainly expressed in higher yielding environments (e.g., eastern Nebraska). The genes on these chromosomes were found to be under additive control meaning that they could be selected for using traditional self-pollinated crop breeding methods. After developing genetic populations segregating for chromosome 3A only, we pinpointed the location of the chromosome 3A gene containing regions. We also found that the favorable allele of one chromosome 3A gene region likely originated from Turkey Red, one of the primary breeding sources of hard red winter wheat cultivars in the Great Plains. Results indicate that many cultivars adapted to lower yielding environments do not contain the favorable chromosome 3A allele. In addition, many modern, high yielding cultivars also do not have the favorable chromosome 3A allele, indicating we have diversified our germplasm and new alleles have been brought into the breeding program in this region.
Technical Abstract: Approximately 20 years ago, we began our efforts to understand grain yield in winter wheat using chromosome substitution lines between Cheyenne and Wichita. We found that two chromosome substitutions, 3A and 6A, greatly affected grain yield. Cheyenne(Wichita 3A) and Cheyenne(Wichita 6A) had 15 to 20% higher grain yield than Cheyenne, and Wichita(Cheyenne 3A) and Wichita(Cheyenne 6A) had 15 to 20% lower grain yield than Wichita. The differences in grain yield are mainly expressed in higher yielding environments (e.g., eastern Nebraska) indicating genotype by environment interactions. In studies using hybrid wheat, the gene action for grain yield on these chromosomes was mainly additive. In subsequent studies, we developed recombinant inbred chromosome lines (RICLS) using monosomics or doubled haploids. In extensive studies we found two regions on 3A affect grain yield in the Cheyenne (RICLs3A) with the positive QTLs coming from Wichita. In Wichita(RICLs3A), we found one main region on 3A that affected grain yield with the negative QTL coming from Cheyenne. The 3A region identified using Wichita(RICLS3A) coincided with one of the regions previously identified in Cheyenne (RICLs3A). As expected the QTLs have their greatest effect in higher yielding environments and also exhibit QTL by environment interactions. The favorable QTL on 3A in Wichita was also found in Turkey Red, the original hard red winter wheat in the Great Plains and presumably the original source of the QTL. Cheyenne, a selection from Crimea, did not have the favorable QTL. In studying modern cultivars, many high yielding cultivars adapted to eastern Nebraska have the Wichita QTL indicating that it was selected for in breeding higher yielding cultivars. However, some modern cultivars adapted to western Nebraska where the QTL has less effect retain the Cheyenne QTL, presumably because the QTL has less effect (is less important in improving grain yield). In addition many modern cultivars have neither the Wichita QTL, nor the Cheyenne QTL indicating we have diversified our germplasm and new alleles have been brought into the breeding program at this region.