Investigating Genetic Progress and Variation for Nitrogen Use Efficiency in Spring Wheat

Abstract

Improved N use efficiency (NUE) increases wheat (Triticum aestivum L.) yields and reduces N losses in the environment. We investigated genetic variation and correlations among agronomic and NUE traits in Canada Western Red Spring wheat cultivars to further improve NUE. Trials were conducted for 3 yr at two locations in Alberta, Canada, under two levels of N (200 and ~50 kg ha−1). Genotype × environment interaction was significant for traits associated with vegetative growth, and genotype × N fertilizer treatment interaction was significant for important yield and NUE traits. There were significant positive correlations between total dry matter and N uptake efficiency (NUpE) in the high (r = 0.74, P < 0.05) and low (r = 0.83, P < 0.05) N treatments. The effect of dwarfing Rht‐1b allele was more prominent under high N treatment in increasing NUE. However, cultivars with Rht‐1b allele showed inconsistent results for NUpE, indicating that Rht alleles might have pleiotropic effects on N uptake. Grain yield, NUE, and N utilization efficiency (NUtE) exhibited genetic improvement over time only under high N treatment. Our results indicated that grain yield increased mainly due to improved harvest index (HI), suggesting improvement in C assimilation rather than N partitioning efficiency. Nitrogen use efficiency may further be improved by intercrossing cultivars with high HI, N harvest index, and NUtE and those with good NUpE, while using total dry matter production as a selection criterion.

There are Different Pathways to Stable Spring Wheat Grain Yield and Nitrogen Utilization Efficiency in Conventional and Organically‐Managed Systems

“…Although the improvement in grain yield has been mainly achieved by increased HI in modern wheat cultivars (Austin et al, 1980;Guttieri et al, 2017;Hay, 1995), these CWRS cultivars have unique characteristics (i.e., weed, disease, and pest suppression and biomass translocation) that appear to help maintain higher grain yields in organic systems. This, in return, supports results of the previous studies that NUtE mainly increased due to improvement in grain yield, which resulted from breeding for disease resistance and grain quality traits in the CWRS class, regardless of management systems (Kubota et al, 2018;Pswarayi et al, 2014).…”

Identification of quantitative trait loci associated with nitrogen use efficiency in winter wheat

“…While the extent of genetic improvement under differing N conditions varied by study, the authors are generally in agreement that direct selection under multiple N rates will accelerate genetic gains in NUE. This hypothesis was further supported by the detection of significant genotype by N rate (G × N) interactions for grain yield and N traits in recent studies of genotypic variation in wheat [9,[12][13]. However, the authors also note that direct selection under multiple N rates may be cost-prohibitive for wheat breeders.…”

Genotypic variation and stability for nitrogen use efficiency in winter wheat

“…In the present studies, G × N rate interactions for grain yield were most commonly observed when lines were tested under three or five N rates. Although exceptions exist (Kubota et al, 2018;Russell et al, 2017), recent investigations of NUE in wheat generally follow a similar trend where significant interactions between wheat genotype and N rate for grain yield were more frequently reported when more than two N rates were used (Barraclough et al, 2010;Büchi et al, 2016;Gaju et al, 2011;Guttieri, Frels, Regassa, Waters, & Baen-ziger, 2017;Latshaw et al, 2016;Mahjourimajd et al, 2016;Ul-Allah et al, 2018). These findings have led many breeders to advocate for direct selection of NUE under reduced N systems in locations that are subjected to N stress each growing season (Brancourt-Hulmel et al, 2005;Cormier et al, 2013;Muellner et al, 2014;Ranjitha et al, 2018).…”

“…In an effort to further increase rates of genetic gains, Cormier et al (2016) hypothesized that selecting wheat lines under multiple N rates may increase yearly improvements, particularly in trials conducted under conditions of moderate N stress. However, recent investigations of N response in wheat have not led to a consensus regarding the occurrence of significant genotype × N rate (G × N) interactions for NUE and N traits in elite wheat germplasm (Bhatta et al, 2017;Büchi et al, 2016;Kubota et al, 2018;Russell, Lee, & Van Sanford, 2017). The contrasting results have prompted some researchers to explore exotic germplasm for sources of genetic variation and led others to doubt the merits of conducting trials under multiple N rates all together (Hawkesford, 2017;Van Deynze et al, 2018).…”