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Grain protein content (GPC) is one of the most important quality traits in wheat, defining the nutritional and end-use properties and rheological characteristics. Over the years, a number of breeding programs have been developed aimed to improving GPC, most of them having been prevented by the negative correlation with grain yield. To overcome this issue, a collection of durum wheat germplasm was evaluated for both GPC and grain protein deviation (GPD) in seven field trials. Fourteen candidate genes involved in several processes related to nitrogen metabolism were precisely located on two high-density consensus maps of common and durum wheat, and six of them were found to be highly associated with both traits. The wheat collection was genotyped using the 90 K iSelect array, and 11 stable quantitative trait loci (QTL) for GPC were detected in at least three environments and the mean across environments by the genome-wide association mapping. Interestingly, seven QTL were co-migrating with N-related candidate genes. Four QTL were found to be significantly associated to increases of GPD, indicating that selecting for GPC could not affect final grain yield per spike. The combined approaches of candidate genes and genome-wide association mapping led to a better understanding of the genetic relationships between grain storage proteins and grain yield per spike, and provided useful information for marker-assisted selection programs.

Projected global climate change is a potential threat for food security. Both rising atmospheric CO₂ concentrations ([CO₂]) and temperatures have significant impacts on crop productivity, but the combined effects on grain quality are not well understood. We conducted an open-air field experiment to determine the impacts of elevated [CO₂] (E-[CO₂], up to 500 μmol mo−1) and warming (+2°C) on grain yield, protein and amino acid (AAs, acid digests) in a rice–winter wheat rotation system for 2 yr. E-[CO₂] increased grain yield by 11.3% for wheat and 5.9% for rice, but decreased grain protein concentration by 14.9% for wheat and by 7.0% for rice, although E-[CO₂] slightly increased the ratio of essential to nonessential AAs. With a consistent decline in grain yield, warming decreased protein yield, notably in wheat, despite a smaller increase in protein concentration. These results indicate that warming could partially negate the negative impact by E-[CO₂] on grain protein concentration at the expense of grain yield; this tradeoff could not fully offset the negative effects of climate change on crop production.

Valorization and utilization of brewers’ spent grain (BSG) are of great interest in terms of reducing food waste and promoting more sustainable food systems. In this study, we aimed to evaluate the nutritional value of upcycled barley/rice proteins (BRP) extracted from BSG and compare this with pea proteins (PP). A randomized, cross-over, double-blind controlled trial was conducted with twelve participants (age: 24 ± 2.8 years, BMI: 23.3 ± 3.0 kg/m2). During three separate visits with a one-week washout period between visits, participants received 20 g BRP, PP, or the benchmark protein whey (WP). Blood-free amino acids (AA) were measured to determine postprandial AA uptake kinetics. The estimated total AA (TAA) uptake of BRP was 69% when compared to WP and 87% when compared to PP. The time to reach the maximum values was similar between the three protein sources. When comparing individual essential AA responses between BRP and PP, we observed higher responses in methionine and tryptophane and lower responses in lysine, histidine, and isoleucine for BRP compared to PP. This study demonstrates that BRP exhibits comparable postprandial TAA uptake profiles to PP. The findings highlight the complementarity of BRP and PP, which may offer the potential for blending approaches to optimize protein quality for overall health.

In plants, carbon and nitrogen (N) economies are intimately linked at the physiological and biochemical level. The strong genetic negative correlation between grain yield and grain protein concentration observed in various cereals is an illustration of this inter-relationship. Studies have shown that deviation from this negative relationship (grain protein deviation or GPD) has a genetic basis, but its physiological basis is still poorly understood. This study analysed data on 27 genotypes grown in multienvironment field trials, representing a wide range of agricultural practices and climatic conditions. The objective was to identify physiological processes related to the genetic variability in GPD. Under most environments, GPD was significantly related to post-anthesis N uptake independently of anthesis date and total N at anthesis. The underlying physiological trait might be related to genotypic differences in either access to soil N, regulation of N uptake by plant N status, or ability to maintain root activity during the grain-filling period. GPD is an interesting potential target in breeding as it appears to be relatively robust across different environments and would be valuable in increasing total N uptake by maturity.

Key messageAn expressed HMW glutenin subunit Glu-Ay showed positive impacts on a range of wheat processing quality and yield traits. The grain protein compositions are significantly optimised for baking, resulting in a better breadmaking quality.The unique breadmaking properties of wheat flour are related to the quality and quantity of high-molecular weight glutenin subunits (HMW-GSs) present in the grain. In the current study, the silent 1Ay HMW-GS allele, present in most bread wheat cultivars, was replaced by the expressed 1Ay21* allele, which was introgressed into Australian bread wheat cultivar Lincoln by a backcrossing and selfing scheme. Stability of gene expression and the effect of the introgressed 1Ay21* subunit on protein composition, agronomic traits, flour functionality, and breadmaking quality were studied using BC4F5 grain grown in glasshouse and field. Field phenotyping and grain quality testing showed that the 1Ay21* gene conferred significant improvements to a range of traits, including an increase in grain protein content by up to 9%, UPP% by up to 24%, bread volume by up to 28%. The glasshouse experiment and one of the field trials showed positive 1Ay21* effects on yield, while one field trial showed one significant effects. This indicates that expression of the 1Ay21* gene has the potential of simultaneously increasing protein content and grain yield under certain environment. The qualitative improvements of the grain also led to a reduction of the energy required during the baking process in addition to the significant positive effects on bread quality.

Improvement of grain protein content (GPC), loaf volume, and resistance to rusts was achieved in 11 Indian wheat cultivars that are widely grown in four different agro-climatic zones of India. This involved use of marker-assisted backcross breeding (MABB) for introgression and pyramiding of the following genes: (i) the high GPC gene Gpc-B1 ; (ii) HMW glutenin subunits 5 + 10 at Glu-D1 loci, and (iii) rust resistance genes, Yr36 , Yr15 , Lr24 , and Sr24 . GPC increased by 0.8 to 3.3%, although high GPC was generally associated with yield penalty. Further selection among high GPC lines allowed identification of progenies with higher GPC associated with improvement in 1000-grain weight and grain yield in the backgrounds of the following four cultivars: NI5439, UP2338, UP2382, and HUW468. The high GPC progenies (derived from NI5439) were also improved for grain quality using HMW glutenin subunits 5 + 10 at Glu-D1 loci. Similarly, progenies combining high GPC and rust resistance were obtained in the backgrounds of following five cultivars: Lok1, HD2967, PBW550, PBW621, and DBW1. The improved pre-bred lines developed following multi-institutional effort should prove a valuable source for the development of cultivars with improved nutritional quality and rust resistance in the ongoing wheat breeding programmes.

Nitrogen supply and post-anthesis temperature affect the protein distribution gradient in the wheat grain endosperm, as measured using a novel image analysis technique for light microscopy sections. Abstract Gradients exist in the distribution of storage proteins in the wheat (Triticum aestivum) endosperm and determine the milling properties and protein recovery rate of the grain. A novel image analysis technique was developed to quantify both the gradients in protein concentration, and the size distribution of protein bodies within the endosperm of wheat plants grown under two different (20 or 28 °C) post-anthesis temperatures, and supplied with a nutrient solution with either high or low nitrogen content. Under all treatment combinations, protein concentration was greater in the endosperm cells closest to the aleurone layer and decreased towards the centre of the two lobes of the grain, i.e. a negative gradient. This was accompanied by a decrease in size of protein bodies from the outer to the inner endosperm layers in all but one of the treatments. Elevated post-anthesis temperature had the effect of increasing the magnitude of the negative gradients in both protein concentration and protein body size, whilst limiting nitrogen supply decreased the gradients.

In common wheat, genes/QTL for a number of traits including grain quality and resistance against all the three rusts were pyramided in the background of an erstwhile elite Indian wheat cv. PBW343. For this purpose, two improved lines (P1 and P2) each in the background of PBW343 were crossed; these two lines were earlier developed using marker-assisted selection (MAS). The genes carried by line “P1” included Yr70 / Lr76  +  Lr37 / Yr17 / Sr38 , and the genes carried by line “P2” included Gpc-B1/Yr36 + QPhs.ccsu-3A.1 + QGw.ccsu-1A.3 + Lr24 / Sr24 + Glu-A1-1 / Glu-A1-2 . Following foreground MAS in F 2 and F 3 and SDS-PAGE analysis in F 5 , 23 lines were selected, each carrying all the genes/QTL for grain quality and resistance to three rusts in homozygous condition. Eleven of the selected lines had relatively higher grain protein content (along with one or more other traits) and were also resistant to five pathotypes of Puccinia triticina (Pt), seven pathotypes of Puccinia graminis f. sp. tritici (Pgt), and two pathotypes (78S84 and 47S103) of Puccinia striiformis f. sp. tritici (Pst) that occur in major wheat-growing areas of India. One line (CCSU-7) out of these 11 selected lines had significantly higher grain yield as well as grain protein content compared with check cv. PBW343, which should prove useful in future wheat breeding programs for improving not only the grain quality but also the durability of resistance against all three rusts.

The grain protein content (GPC) of rice is an important factor that determines its nutritional, cooking, and eating qualities. To date, although a number of genes affecting GPC have been identified in rice, most of them have been cloned using mutants, and only a few genes have been cloned in the natural population. In this study, 135 significant loci were detected in a genome-wide association study (GWAS), many of which could be repeatedly detected across different years and populations. Four minor quantitative trait loci affecting rice GPC at four significant association loci, qPC2.1 , qPC7.1 , qPC7.2 , and qPC1.1 , were further identified and validated in near-isogenic line F 2 populations (NIL-F 2 ), explaining 9.82, 43.4, 29.2, and 13.6% of the phenotypic variation, respectively. The role of the associated flo5 was evaluated with knockdown mutants, which exhibited both increased grain chalkiness rate and GPC. Three candidate genes in a significant association locus region were analyzed using haplotype and expression profiles. The findings of this study will help elucidate the genetic regulatory network of protein synthesis and accumulation in rice through cloning of GPC genes and provide new insights on dominant alleles for marker-assisted selection in the genetic improvement of rice grain quality.

Public awareness is gradually growing in favour of consuming nutritionally superior brown and pigmented rice which is in general relatively poor in eating and cooking quality. Understanding inheritance pattern of nutritional and quality traits is prerequisite for further improvement exercising molecular tools. A holistic approach was adopted to identify unique and common genomic regions regulating 17 grain nutritional as well as physiochemical traits using a diverse panel of 96 rice genotypes. Seventy eight significant marker-trait associations distributed in all chromosomes with phenotypic variance ranging from 4 to 27% were detected. Marker RM 467 was co-localized with previously identified QTL qPC10.1 and gene OsGluA2. Grain protein and metal content were associated with cooking quality which was also supported by the marker-trait association. Two QTLs for each of grain protein and amylose content (AC) with associated markers RM 17600 and RM 1272 were found co-localized with additive effect in opposite direction. Similarly, RM 162 was associated with both zinc content and cooking time (alkali spreading value). Iron content was also associated with grain size which was supported by the association of RM8050 with the both Fe content and kernel length/breadth ratio. Phenotypically pigmented rice was detected with low AC and one genetic locus for anthocyanin (qANTH5.1) was also found to be co-localized with a QTL for AC (qAC5.1) with additive effect in opposite direction. Co-localized associated loci for nutritional and cooking and eating quality can guide strategic biofotification programs for improving rice for nutritional traits without distracting consumer preference.