Genetic Basis for Variation in Wheat Grain Yield in Response to Varying Nitrogen Application

Abstract

Nitrogen (N) is a major nutrient needed to attain optimal grain yield (GY) in all environments. Nitrogen fertilisers represent a significant production cost, in both monetary and environmental terms. Developing genotypes capable of taking up N early during development while limiting biomass production after establishment and showing high N-use efficiency (NUE) would be economically beneficial. Genetic variation in NUE has been shown previously. Here we describe the genetic characterisation of NUE and identify genetic loci underlying N response under different N fertiliser regimes in a bread wheat population of doubled-haploid lines derived from a cross between two Australian genotypes (RAC875 × Kukri) bred for a similar production environment. NUE field trials were carried out at four sites in South Australia and two in Western Australia across three seasons. There was genotype-by-environment-by-treatment interaction across the sites and also good transgressive segregation for yield under different N supply in the population. We detected some significant Quantitative Trait Loci (QTL) associated with NUE and N response at different rates of N application across the sites and years. It was also possible to identify lines showing positive N response based on the rankings of their Best Linear Unbiased Predictions (BLUPs) within a trial. Dissecting the complexity of the N effect on yield through QTL analysis is a key step towards elucidating the molecular and physiological basis of NUE in wheat.

Effect of Deprivation and Excessive Application of Nitrogen on Nitrogen Use Efficiency‐Related Traits Using Wheat Cultivars, Lines, and Landraces

“…The reported negative correlation between NUE and N supply is in agreement with previous studies (Kichey et al, 2007;Mahjourimajd et al, 2016;Daba, 2018) in which they showed that the highest NUE was obtained at lower N supply. Todeschini et al (2016) indicated that among six wheat cultivars, five had higher NUE at low N supply.…”

“…This result is in agreement with those of Guttieri et al (2017). Moreover, the strong negative correlation between GY and GPC observed in this study is well established and has a genetic basis (Le Gouis et al, 2000;Lopes and Reynolds, 2012;Cormier et al, 2013;Mahjourimajd et al, 2016). Moreover, the strong negative correlation between GY and GPC observed in this study is well established and has a genetic basis (Le Gouis et al, 2000;Lopes and Reynolds, 2012;Cormier et al, 2013;Mahjourimajd et al, 2016).…”

“…Todeschini et al (2016) indicated that among six wheat cultivars, five had higher NUE at low N supply. The current study, as well as several others (Cormier et al, 2013;Mahjourimajd et al, 2016), suggested the need for a better definition for NUE due to the criticisms that have been reported for the initial NUE (calculated according to Moll et al, 1982) that focus only on productivity. The current study, as well as several others (Cormier et al, 2013;Mahjourimajd et al, 2016), suggested the need for a better definition for NUE due to the criticisms that have been reported for the initial NUE (calculated according to Moll et al, 1982) that focus only on productivity.…”

“…The analysis of genotypes' response to N supply across environments was estimated using the regression coefficient (b i ) (Eberhart and Russell, 1966) and the N responsiveness (NR) values (Mahjourimajd et al, 2016). When GY increase due to increased N supply was low, genotypes were considered nonresponsive (N stable).…”

“…When GY increase due to increased N supply was low, genotypes were considered nonresponsive (N stable). The analysis of genotypes' response to N supply across environments was estimated using the regression coefficient (b i ) (Eberhart and Russell, 1966) and the N responsiveness (NR) values (Mahjourimajd et al, 2016). The b i reflects the slope of the curves that represent the change in GY with the change in N supply.…”