Contents lists available at ScienceDirect Field Crops Research journal homepage: www.elsevier.com/locate/fcr The combination of dwarfing genes Rht4 and Rht8 reduced plant height, improved yield traits of rainfed bread wheat (Triticum aestivum L.) Yingying Du a,1 , Liang Chen a,1 , Yushen Wang a , Zhiyuan Yang a , Iqbal Saeed a , Bachir Goudia Daoura a , Yin-Gang Hu a,b, ⁎ a State Key Laboratory of Crop Stress Biology for Arid Areas, College of Agronomy, Northwest A & F University, Yangling, Shaanxi, 712100, P.R. China b Institute of Water Saving Agriculture in Arid Regions of China, Yangling, Shaanxi, 712100, PR China ARTICLE INFO Keywords: Bread wheat Dwarfing gene Rht4 Early vigor Plant height Grain yield ABSTRACT The utilization of dwarfing genes in wheat breeding has reduced plant height, improved lodging resistance and increased the harvest index. The effects of dwarf genes Rht4 and Rht4 + Rht8 on early vigor, morphology and grain yield traits in bread wheat were evaluated using the F 4 ,F 5 and F 6 dwarf lines derived from Chinese wheat cultivars Xifeng20 and Jinmai47 (with Rht8) with Burt ert 937 (Rht4 donor) in three crop seasons under rainfed conditions. The results showed that Rht4 did not affect coleoptile length but increased maximum length, total length and surface area of roots, while root diameter was reduced. Compared with their tall parents, plant height was reduced by 8.8–15.3% and 7.4–17.7% in the Rht4 and Rht4 + Rht8 dwarf lines, respectively. The length and diameter of the internodes other than the peduncle was significantly reduced. The length, width and area of flag leaf were not affected in the Rht4 + Rht8 dwarf lines but were increased in the Rht4 dwarf lines. Grain number per spike was reduced in the Rht4 and Rht4 + Rht8 dwarf lines. Finally, the 1000–kernal weight, aboveground biomass and grain yield were also reduced in the Rht4 dwarf lines, while they were increased in the Rht4 + Rht8 dwarf lines. These results revealed that the dwarfing gene Rht4 had moderate effects on plant height and the combinations of Rht4 and Rht8 could reduce plant height to a desirable level and improve yield-related traits in the rainfed cultivation. 1. Introduction Dwarfing genes have been widely used in bread wheat breeding to reduce plant height, improve lodging resistance and convert more photosynthate to grain yield (Rebetzke et al., 2012). Dwarfing genes Rht-B1b and Rht-D1b are gibberellin insensitive (GAI), leading to de- creased sensitivity of vegetative tissues to endogenous gibberellins and, consequently, to reductions in stem internode length and reduce overall plant height (Keyes et al., 1989; Hoogendoorn et al., 1990; Keyes et al., 1990), thereby allowing more assimilate to pass to florets, increasing floret survival and potential grain number (Hoogendoorn et al., 1990). The gibberellin-responsive (GAR) dwarfing genes, such as Rht8, Rht12 and Rht13, can reduce plant height by 7%, 40–45% and 34%, respec- tively, through shortening the lengths of different internodes (Gasperini et al., 2012; Chen et al., 2013; Chen et al., 2014; Daoura et al., 2014; Wang et al., 2015). The coleoptile protects the elongating seedling as it emerges through the soil surface. A shorter coleoptile will tend to result in poor establishment if seeds are sown too deep under drought conditions. Improved seedling establishment and rapid leaf area development contribute to greater groundcover early in the season. In rainfed en- vironments, such as in northwest China, poor ground cover will reduce competitiveness with weeds and increase soil water loss through eva- poration. In turn, water use efficiency, biomass and, ultimately, grain yield are likely to decrease (Botwright et al., 2002). Dwarfing genes Rht-B1b and Rht-D1b reduced cell length and width and result in shorter coleoptile and peduncle length (Botwright et al., 2005). Unlike Rht-B1b and Rht-D1b, GAR dwarfing genes have no negative effects on coleoptile length and seeding vigor and therefore may be adapted for deep sowing and potential use in wheat crop improvement for rainfed environments (Gasperini et al., 2012; Chen et al., 2013; Chen et al., 2014; Daoura et al., 2014; Wang et al., 2015), especially since the changes to early vigor, cell number and size in wheat with Rht8 was independent of plant height (Botwright et al., 2005). Enhanced responsiveness to gib- berellins could also contribute to improved early vigor and reduce water loss from the soil and thereby improve competitiveness with http://dx.doi.org/10.1016/j.fcr.2017.10.015 Received 4 June 2017; Received in revised form 23 September 2017; Accepted 18 October 2017 ⁎ Corresponding author at: State Key Laboratory of Crop Stress Biology for Arid Areas, College of Agronomy, Northwest A & F University, Yangling, Shaanxi, 712100, P.R. China. 1 These two authors contributed equally to this work. E-mail address: huyingang@nwsuaf.edu.cn (Y.-G. Hu). Field Crops Research 215 (2018) 149–155 Available online 06 November 2017 0378-4290/ © 2017 Elsevier B.V. All rights reserved. MARK