NARDI FUNDULEA, ROMANIA ROMANIAN AGRICULTURAL RESEARCH, NO. 37, 2020 www.incda-fundulea.ro Print ISSN 1222‒4227; Online ISSN 2067‒5720 ________________________________________ Received 12 August 2019; accepted 5 September 2019. First Online: September, 2019. DII 2067-5720 RAR 2020-17 RELATIONSHIP OF SEMINAL ROOTS ANGLE AND GRAIN YIELD OF WINTER WHEAT CULTIVARS UNDER THE CONTINENTAL CLIMATE OF ROMANIA Elena Petcu * , Cătălin Lazăr, Cristina Marinciu, Nicolae N. Săulescu National Agricultural Research and Development Institute Fundulea, 915200 Fundulea, Călăraşi County, Romania * Corresponding author. E-mail: petcue@ricic.ro ABSTRACT Root system traits are important for accessing water from different soil depths, for nutrient capture from the soil profile and for plant anchorage influence on lodging resistance. All these can have complex and sometimes contradictory effects on grain yield. Wheat root system architecture is closely related to seminal roots axis angle in the seedlings stage. Our research is an attempt to define the most desirable seminal root angle for the continental climate of Romania, by studying its correlation with grain yield of several winter wheat cultivars tested in a representative sample of 108 yield trials, covering a wide range of environmental conditions. Correlation coefficients varied from -0.46 to +0.77, with an average of +0.17. In most yield trials correlations were positive, but low and mostly not significant. This suggests that for most of Romania and for regions with similar conditions, winter wheat breeding should aim at creating mainly cultivars with large seminal roots angle that could better use rainfall falling during the vegetation season, but also cultivars with a small seminal roots angle that can improve the access to water in the soil depth profile during severe drought conditions. Keywords: root system architecture, seminal roots angle, yield, drought, nutrient capture. INTRODUCTION oot system architecture plays an important role in determining crops efficiency. First, root system architecture has important functional implications for water extracted from the soil (Blum and Arkin, 1984; Manschadi et al., 2006). But root system architecture is also important for nutrient use efficiency (Lynch, 2019). By exploring the subsoil, a steep and deep root system is beneficial not only for accessing water from the soil depth (Singh et al., 2011), but also for N capture from the soil profile. In contrast, a shallow but dense root system is not only better for using rainfall during the vegetation season (Liao et al., 2006), but also has advantages regarding P capture and should also be useful for capture of K, Ca, and Mg in acid soils (Lynch, 2019). Finally, the root system is important in wheat for lodging resistance, by its effect on anchorage strength. Crook and Ennos (1994) reported that plants with stronger, more widely spread coronal roots produced larger soil cones during anchorage failure and resisted larger forces, while Pinthus (1967) found high correlations between root spreading angles and lodging rates from a series of field trials grown under various environmental conditions. There is a large genotypic variation in crop plant root systems, that could be exploited in breeding programs (O’Toole and Bland, 1987; Fukai and Cooper, 1995; Kato et al., 2006; Manschadi et al., 2008), but not much progress has been made so far, because of difficulties in studying and selecting for improved root systems. The root system traits expressed in the early development stages (seminal roots angle and number) were found to be associated with the root system architecture of the mature plants (Richard et al., 2015), the differences in the seminal roots angle being related to the horizontal and vertical exploration of the soil. This allowed the development of a rapid method for high- throughput phenotyping of seminal root traits in wheat, which opened new perspectives in R