A novel approach to identify genes that determine grain protein deviation in cereals

Abstract

SummaryGrain yield and protein content were determined for six wheat cultivars grown over 3 years at multiple sites and at multiple nitrogen (N) fertilizer inputs. Although grain protein content was negatively correlated with yield, some grain samples had higher protein contents than expected based on their yields, a trait referred to as grain protein deviation (GPD). We used novel statistical approaches to identify gene transcripts significantly related to GPD across environments. The yield and protein content were initially adjusted for nitrogen fertilizer inputs and then adjusted for yield (to remove the negative correlation with protein content), resulting in a parameter termed corrected GPD. Significant genetic variation in corrected GPD was observed for six cultivars grown over a range of environmental conditions (a total of 584 samples). Gene transcript profiles were determined in a subset of 161 samples of developing grain to identify transcripts contributing to GPD. Principal component analysis (PCA), analysis of variance (ANOVA) and means of scores regression (MSR) were used to identify individual principal components (PCs) correlating with GPD alone. Scores of the selected PCs, which were significantly related to GPD and protein content but not to the yield and significantly affected by cultivar, were identified as reflecting a multivariate pattern of gene expression related to genetic variation in GPD. Transcripts with consistent variation along the selected PCs were identified by an approach hereby called one-block means of scores regression (one-block MSR).

Understanding the Interactions between Biomass, Grain Production and Grain Protein Content in High and Low Protein Wheat Genotypes under Controlled Environments

“…The lower average GPC of Mace in NVT data might be due to its higher yield at some of the sites compared with Gregory and Impala. Mace is adapted to the low-yielding environments of southern Australia [49] and its GPC tends to drop at high yielding sites [50]. In this context, the grain protein deviation of Mace, after Spitfire, was higher than the other four genotypes (Supplementary Figure S2B).…”

Perspective on Wheat Yield and Quality with Reduced Nitrogen Supply

“…This protein concentration requires high fertilizer rates after anthesis, for high buildup of storage protein. Despite large efforts by breeders, the negative relationship of yield with grain protein concentration is difficult to break ( Figure 2 A) [30] , although grain quality of modern varieties has increased by enhancing storage protein concentration (measured by near infrared spectroscopy-N content) in the grain ( Figure 2 B). Because of increased N fertilizer and genotypic improvement, the protein concentration in grains, on average, in German wheat genotypes rose from about 7–8% crude protein in the 1960s to 12–16% in modern genotypes ( Figure 2 B) [31] .…”

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Figure 2 Relationship of Yield with Grain Protein Concentration. (A) Negative correlation of single-year grain nitrogen (N) concentrations of six British wheat varieties (different colors), with yield at three N levels: 100 kg/ha (squares), 200 kg/ha (triangles), and 250 kg/ha (open squares) [30] . DM, dry matter.

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Genetic variation and heritability of grain protein deviation in European wheat genotypes

“…On the other hand, the post-anthesis N uptake rather than remobilization or total N content at anthesis was significantly positively correlated with GPD in 12 of the growth environments, with correlation coefficients ranging from 0.44 to 0.76, and close to significant in others. Mosleth et al (2015) compared the patterns of gene expression in developing grain of six genotypes differing in GPD, identifying gene transcripts which were associated with both positive and negative GPD.…”

“…The analysis of GPD is challenging because both grain protein and grain yield exhibit strong genotype x environment (G x E) interactions, including effects of N fertilization where this is included as a factor. We therefore developed a statistical approach to dissociate differences in grain protein content from direct effects of nitrogen availability and indirect effects of yield (Mosleth et al, 2015). This analysis was initially applied to a set of 6 cultivars grown on two sites over three growth years.…”