Yingang Hu1, 2, Liang Chen1, Yushen Wang1
1.State Key Lab of Crop Stress Biology for Arid Areas and College of Agronomy,
 Northwest A&F University
2.Institute of Water-saving Agriculture for Arid Regions of China,
Northwest A&F University

Wheat is one of the most important grain crops in the world. Drought is one of the most important factors limiting wheat production and yield stability. Understanding the effects of wheat dwarfing genes on drought tolerance and yield potential related traits is crucial for the proper utilization of dwarfing genes in wheat improvement for drought tolerance.
The analysis on the effects of dwarfing genes Rht-B1b, Rht-D1b and Rht8found that GAI dwarfing genes Rht-B1band Rht-D1bwere mostly utilized in theregion, where rainfall was relatively plenty for wheat production or with irrigation; while GAR dwarfing gene Rht8had extensive distribution in various ecological regions, where most of the regions were rainfed areas or with limited irrigation.It seemed that GAR dwarfing genes may be better for improving water use efficiency and wheat yield potential?To evaluate the effects of GAR dwarfing genes on drought tolerance and yield potential of wheat, the populations and lines with GAR dwarfing genes, were constructed, such as Rht12 and Rht13.
Results indicated thatRht12 shortened final plant stature by 40%, and increased the thickness of the internode walls and width of the leaves; Rht12 did not adversely affected the seedling vigour, especially coleoptile length and root traits at the seedling stage; Rht12 elongated the duration of the spike development phase, improved the proportion of spike dry weight at anthesis and significantly increased floret fertility (14%) in the autumn sowing experiment; Rht12 delayed anthesis date by around 5 days and even the dominant Vrn-B1 allele could not compensate this negative effect. Additionally, grain size was reduced; finally, grain yield was similar between the dwarf and tall lines in the autumn sowing experiment.Rht12 could substantially reduce plant height without altering seeding vigour and significantly increase spikelet fertility in the favorable autumn sowing environment.
Results indicated thatRht13 had stronger effect on plant height reduction than that of Rht8. Coleoptile length and root characters were not affected by Rht8 and Rht13. Grain number per spike was significantly reduced by Rht13 while Rht8 had no significant effect on grain number per spike. Rht13 and Rht8 reduced biomass plant-1 by 27.9% and 25.2% and grain yield plant-1 by 29.0% and 17.4%, respectively. Rht13 had no significant effect on 1000-kernel weight and harvest index, whereas Rht8 increased 1000-kernel weight by 6.9% and harvest index by 10.4%.
To broaden the utilization of GAR dwarfing genes in wheat, we have developed a few populations with the GAR dwarfing genes, such as Rht4, Rht15 and Rht18 etc to clarify their effects on drought tolerance and yield related traits, so that novel GAR dwarfing genes could be utilized in breeding programs for improving drought tolerance and yield potential of wheat in dryland and irrigation-limited areas.