Comparative study of the genetic basis of nitrogen use efficiency in wild and cultivated barley

Abstract

To curb the increasing demand for nitrogenous fertilizers, it is imperative to develop new cultivars with comparatively greater nitrogen use efficiency (NUE). Nonetheless, so far very meager information is available concerning the variances among barley (Hordeum vulgare L.) varieties for their response to nitrogen deprivation. The current study was carried out to explore the potential of barley genotypes for higher NUE. A hydroponic experiment was conducted at seedling stage to compare the performance of four barley genotypes, ZD9 and XZ149 (with higher NUE) and HXRL and XZ56 (with lower NUE) in response to low (0.1 mM) and normal nitrogen (2 mM) levels. Under low N, all the genotypes expressed less number of tillers, decreased soluble proteins, chlorophyll and N concentrations in both roots and shoots, in comparison with normal N supply. However, significant differences were found among the genotypes. The genotypes with high NUE (ZD9 and XZ149) showed higher N concentration, increased number of tillers, improved chlorophyll and soluble proteins in both roots and shoots as compared to the inefficient ones (HXRL and XZ56). Furthermore, nitrate transporter gene (NRT2.1) showed higher expression under low N, both in roots and leaves of N efficient genotypes, as compared to the N inefficient ones. However, N assimilatory genes (GS1 and GS2) showed higher expression under normal and low N level, in leaves and roots respectively. The outcome of the study revealed that genotypes with higher NUE (ZD9 and XZ149) performed better under reduced N supply, and may require relatively less N fertilizer for normal growth and development, as compared to those with lower NUE. The study also revealed a time-specific expression pattern of studied

Genetic regulation of the traits contributing to wheat nitrogen use efficiency

“…The NRT2 gene family has also been reported in model crop species, including tobacco [44], M. truncatula [45], tomato [34] and soybean [46], and also in cereal/grass crop species, including barley [38], rice (Oryza sativa) [47], maize [48], sorghum [49] and Brachypodium [50]. Phylogenetic analysis demonstrated that the NRT2 genes of grass and cereals positioned distantly from that of A. thaliana, which make it hard to predict the function of those genes in grass and cereals based on functional characterisation in A. thaliana [13].…”

“…The pioneer investigations on NRT1 was conducted with A. thaliana due to the ease of obtaining mutants and transgenic plants [33]. However, close homologues of the A. thaliana NRT1 gene have been identified in other species such as tomato [34] and M. truncatula [35] and in cereals including rice [36], sugarcane [37], barley [38], maize [39], and wheat [40]. Until now, the functional characterization of this gene family has not been conducted in many crop species including wheat.…”

Genome editing to re-domesticate and accelerate use of barley crop wild relatives

“…Nitrogen use efficiency (NUE) is increasingly important (Ekardt et al, 2018). Studies with wild barley suggest that it inherits improved NUE and could be a valuable source for new alleles (Shah et al, 2017(Shah et al, , 2019Zahn et al, 2020). Rehman et al (2021) screened wild barley accessions and found several accessions that were less susceptible to common diseases (net blotch, scald, leaf rust and powdery mildew).…”

“…Phenotyping technologies may be used to screen CWR directly, followed by crossing of the CWR with a cultivar with a suitable genetic background and then selection, or conversely, CWR may be crossed with domesticated lines first, followed by evaluation of the F 1 ; both strategies involve advancement and screening of multiple subsequent backcross generations (Dempewolf et al, 2017;Zhang et al, 2022). Identification of the specific genes or quantitative trait loci (QTL) conferring resistance or tolerance to the target trait(s) can speed up the process of ensuring relevant genes are introgressed through markerassisted selection (Swamy and Sarla, 2008;Sharma et al, 2013;Migicovsky and Myles, 2017). There are some examples where this type of pre-breeding work has paid dividends.…”

Transcriptome Analysis Reveals Different Responsive Patterns to Nitrogen Deficiency in Two Wheat Near-Isogenic Lines Contrasting for Nitrogen Use Efficiency

“…Additionally, plant genetic information is also an important approach to improve NUE [ 15 ]. For instance, Shah et al [ 16 ] reported that the NRT2.1 expression level in the N-efficient genotypes was higher than that in the inefficient ones in barley under low-N stress. Likewise, Wei et al [ 17 ] found that overexpression of TaGS2 may improve nitrogen assimilation under N-deficit conditions.…”