A wheat/rye polymorphism affects seminal root length and yield across different irrigation regimes

Alien introgression to wheat for food security: functional and nutritional quality for novel products under climate change

Crop yield and quality has increased globally during recent decades due to plant breeding, resulting in improved food security. However, climate change and shifts in human dietary habits and preferences display novel pressure on crop production to deliver enough quantity and quality to secure food for future generations. This review paper describes the current state-of-the-art and presents innovative approaches related to alien introgressions into wheat, focusing on aspects related to quality, functional characteristics, nutritional attributes, and development of novel food products. The benefits and opportunities that the novel and traditional plant breeding methods contribute to using alien germplasm in plant breeding are also discussed. In principle, gene introgressions from rye have been the most widely utilized alien gene source for wheat. Furthermore, the incorporation of novel resistance genes toward diseases and pests have been the most transferred type of genes into the wheat genome. The incorporation of novel resistance genes toward diseases and pests into the wheat genome is important in breeding for increased food security. Alien introgressions to wheat from e.g. rye and Aegilops spp. have also contributed to improved nutritional and functional quality. Recent studies have shown that introgressions to wheat of genes from chromosome 3 in rye have an impact on both yield, nutritional and functional quality, and quality stability during drought treatment, another character of high importance for food security under climate change scenarios. Additionally, the introgression of alien genes into wheat has the potential to improve the nutritional profiles of future food products, by contributing higher minerals levels or lower levels of anti-nutritional compounds into e.g., plant-based products substituting animal-based food alternatives. To conclude, the present review paper highlights great opportunities and shows a few examples of how food security and functional-nutritional quality in traditional and novel wheat products can be improved by the use of genes from alien sources, such as rye and other relatives to wheat. Novel and upcoming plant breeding methods such as genome-wide association studies, gene editing, genomic selection and speed breeding, have the potential to complement traditional technologies to keep pace with climate change and consumer eating habits.

Chasing high and stable wheat grain mineral content: Mining diverse spring genotypes under induced drought stress

Climate change-induced drought has an effect on the nutritional quality of wheat. Here, the impact of drought at different plant stages on mineral content in mature wheat was evaluated in 30 spring-wheat lines of diverse backgrounds (modern, old and wheat-rye-introgressions). Genotypes with rye chromosome 3R introgression showed a high accumulation of several important minerals, including Zn and Fe, and these also showed stability across drought conditions. High Se content was found in genotypes with chromosome 1R. Old cultivars (K, Mg, Na, P and S) and 2R introgression lines (Fe, Ca, Mn, Mg and Na) demonstrated high mineral yield at early and late drought, respectively. Based on the low nutritional value often reported for modern wheat and negative climate effects on the stability of mineral content and yield, genes conferring high Zn/Fe, Se, and stable mineral yield under drought at various plant stages should be explicitly explored among 3R, 1R, old and 2R genotypes, respectively.

Preserving root stem cell functionality under low oxygen stress: the role of nitric oxide and phytoglobins

MAIN CONCLUSION

The preservation of quiescent center stem cell integrity in hypoxic roots by phytoglobins is exercised through their ability to scavenge nitric oxide and attenuate its effects on auxin transport and cell degradation. Under low oxygen stress, the retention or induction of phytoglobin expression maintains cell viability while loss or lack of induction of phytoglobin leads to cell degradation. Plants have evolved unique attributes to ensure survival in the environment in which they must exist. Common among the attributes is the ability to maintain stem cells in a quiescent (or low proliferation) state in unfriendly environments. From the seed embryo to meristematic regions of the plant, quiescent stem cells exist to regenerate the organism when environmental conditions are suitable to allow plant survival. Frequently, plants dispose of mature cells or organs in the process of acclimating to the stresses to ensure survival of meristems, the stem cells of which are capable of regenerating cells and organs that have been sacrificed, a feature not generally available to mammals. Most of the research on plant stress responses has dealt with how mature cells respond because of the difficulty of specifically examining plant meristem responses to stress. This raises the question as to whether quiescent stem cells behave in a similar fashion to mature cells in their response to stress and what factors within these critical cells determine whether they survive or degrade when exposed to environmental stress. This review attempts to examine this question with respect to the quiescent center (QC) stem cells of the root apical meristem. Emphasis is put on how varying levels of nitric oxide, influenced by the expression of phytoglobins, affect QC response to hypoxic stress.

Development and Identification of a Wheat-Rye Breeding Line for Harmonious Improvement Between Powdery Mildew Resistance and High Yield Potential

Powdery mildew, caused by Blumeria graminis f. sp. tritici, is a devastating disease that seriously threatens wheat yield and quality. To control this disease, host resistance is the preferred measure. However, wheat breeding is a complex process with elusive exchange and recombination of the traits from their parents. Increased resistance often leads to a decline in other key traits, such as yield and quality. Developing breakthrough germplasms with harmonious powdery mildew resistance and other key breeding traits is attractive in wheat breeding. In this study, we developed an ideal wheat breeding line AL46 that pyramided its hexaploid triticale parent-derived desirable yield traits and its wheat parent-derived powdery mildew resistance gene Pm2. Sequential genomic in situ hybridization (GISH), multicolor GISH, multicolor fluorescence in situ hybridization, and molecular marker analyses revealed that AL46 was a wheat-rye T1RS·1BL translocation line. Genetic analysis combined with function marker detection and sequence alignment were used to confirm that AL46 carried the Pm2 gene. Then, we evaluated the powdery mildew resistance and comprehensive traits of AL46, and just as we designed, AL46 showed harmonious powdery mildew resistance with some key breeding traits. This study not only developed an ideal wheat germplasm resource but also provided a successful example for pyramiding breeding, which could be a promising direction for wheat improvement in the future.

Effects of substituting wheat by rye in diets for young fattening pigs on nutrient digestibility, performance, products of intestinal fermentation, and fecal characteristics

Climate change and increasing demands to reduce the environmental impact of feed production are major challenges for animal nutritionists. Compared to wheat, which is commonly used in high levels in European piglet diets, rye is more efficient in using limited resources, most importantly, water and phosphorus. As a result, its cultivation has a relatively low carbon footprint. The high amounts of non-starch polysaccharides of rye might lead to an increased intestinal fermentation with potential beneficial effects on gut health. However, the high levels of non-starch polysaccharides in rye, which have a major impact on the physico-chemical conditions of the digesta, might affect digestibility and performance especially in young animals. It was therefore of interest to compare the effects of isoenergetic diets with increasing levels of rye as a replacement for wheat fed to young fattening pigs (bodyweight: 16-40 kg). The control diet contained 69% of wheat, while in the other three experimental diets, the amount of wheat was gradually replaced (by a third in each case) with rye. Thus, the experimental diets contained 23, 46, and 69% of rye. A total of 40 young pigs were housed individually in four dietary treatment groups. During a 4 week trial, effects on performance, digestibility, products of intestinal fermentation, and fecal characteristics were evaluated. There were no negative effects on feed intake and gains, even though the feed conversion ratio increased with the highest dietary rye level (69%). Digestibility rates of organic matter and crude protein did not differ significantly. Without affecting the characteristics of the feces, numerically higher amounts of intestinal fermentation products and higher colonic digesta mass were observed.

Root Distribution of Tomato Cultivated in Greenhouse under Different Ventilation and Water Conditions

Mastering root distribution is essential for optimizing the root zone environment and for improving water use efficiency, especially for crops cultivated in greenhouses. Here, we set up two irrigation amount levels based on measurements of the cumulative 20 cm pan evaporation (E_p) (i.e., K_0.9: 0.9 E_p; K_0.5: 0.5 E_p), and three ventilation modes through opening the greenhouse vents at different locations (T_R: open the roof vents only; T_RS: open both the roof and south vents; T_S: open the south vents only) to reveal the effects of the ventilation mode and irrigation amount on the root distribution of greenhouse tomato. Six treatments were designed in blocks with the ventilation mode as the main treatment and the irrigation amount as the vice treatment. On this basis, the normalized root length density (NRLD) model of six treatments was developed by considering air environment, soil water and temperature conditions, root length density (RLD) and yield. The results showed that air speed of the T_RS was significantly higher than T_R and T_S (p < 0.01), and the air temperature and relative humidity under different ventilation showed the rule: T_R > T_S > T_RS. There was a significant third-order polynomial function relationship between NRLD and soil depth, and the coefficient of the cubic term (R₀) had a bivariate quadratic polynomial function relationship with irrigation amount and air speed (determination coefficient, R² = 0.86). Root mean square errors of the simulated and measured value of NRLD under T_R, T_RS and T_S were 0.20, 0.23 and 0.27 in 2020, and 0.31, 0.23 and 0.28 in 2021, respectively, normalized root mean squared errors were 15%, 17%, 20% in 2020, and 23%, 18% and 21% in 2021. The RLD distribution ratio from the ground surface to a one-quarter relative root depth was 74.1%, and 88.0% from the surface to a one-half relative root depth. The results of the yield showed that a better combination of ventilation and irrigation was recommended as T_RS combined with K_0.9.

Dosage differences in 12-OXOPHYTODIENOATE REDUCTASE genes modulate wheat root growth

Wheat, an essential crop for global food security, is well adapted to a wide variety of soils. However, the gene networks shaping different root architectures remain poorly understood. We report here that dosage differences in a cluster of monocot-specific 12-OXOPHYTODIENOATE REDUCTASE genes from subfamily III (OPRIII) modulate key differences in wheat root architecture, which are associated with grain yield under water-limited conditions. Wheat plants with loss-of-function mutations in OPRIII show longer seminal roots, whereas increased OPRIII dosage or transgenic over-expression result in reduced seminal root growth, precocious development of lateral roots and increased jasmonic acid (JA and JA-Ile). Pharmacological inhibition of JA-biosynthesis abolishes root length differences, consistent with a JA-mediated mechanism. Transcriptome analyses of transgenic and wild-type lines show significant enriched JA-biosynthetic and reactive oxygen species (ROS) pathways, which parallel changes in ROS distribution. OPRIII genes provide a useful entry point to engineer root architecture in wheat and other cereals.

Development and identification of an elite wheat-Hordeum californicum T6HcS/6BL translocation line ND646 containing several desirable traits

Hordeum californicum (H. californicum, 2n=2X=14, H^cH^c), one of the wild relatives of wheat (Triticum aestivum L.), harbors many desirable genes and is a potential genetic resource for wheat improvement. In this study, an elite line ND646 was selected from a BC₄F₅ population, which was developed using ⁶⁰Co-γ irradiated wheat-H. californicum disomic addition line WJ28-1 (DA6H^c) as the donor parent and Ningchun 4 as the recurrent parent. ND646 was identified as a novel wheat-H. californicum 6H^cS/6BL translocation line using genomic in situ hybridization (GISH), fluorescence in situ hybridization (FISH), and H. californicum-specific expressed sequence tag (EST) markers. Further evaluation revealed that ND646 had excellent performance in several traits, such as a higher sedimentation value (SV), higher water absorption rate (WAR), and higher hardness index (HI). More importantly, it had more kernels per spike (KPS), a higher grain yields (GY), and good resistance to powdery mildew, leaf rust, and 2,4-D butylate (2,4-D). Its excellent phenotypic performance laid the foundation for further investigation of its genetic architecture and makes ND646 a useful germplasm resource for wheat breeding.

Climate Change Impact on Wheat Performance—Effects on Vigour, Plant Traits and Yield from Early and Late Drought Stress in Diverse Lines

Global climate change is threatening wheat productivity; improved yield under drought conditions is urgent. Here, diverse spring-wheat lines (modern, old and wheat-rye introgressions) were examined in an image-based early-vigour assay and a controlled-conditions (Biotron) trial that evaluated 13 traits until maturity. Early root vigour was significantly higher in the old Swedish lines (root length 8.50 cm) and introgressed lines with 1R (11.78 cm) and 1RS (9.91 cm) than in the modern (4.20 cm) and 2R (4.67 cm) lines. No significant correlation was noted between early root and shoot vigour. A higher yield was obtained under early drought stress in the 3R genotypes than in the other genotype groups, while no clear patterns were noted under late drought. Evaluating the top 10% of genotypes in terms of the stress-tolerance index for yield showed that root biomass, grains and spikes per plant were accountable for tolerance to early drought, while 1000-grain weight and flag-leaf area were accountable for tolerance to late drought. Early root vigour was determined as an important focus trait of wheat breeding for tolerance to climate-change-induced drought. The responsible genes for the trait should be searched for in these diverse lines. Additional drought-tolerance traits determined here need further elaboration to identify the responsible genes.

Molecular Cytogenetic Identification of a New Wheat-Rye 6R Addition Line and Physical Localization of Its Powdery Mildew Resistance Gene

Rye (Secale cereale L.), a naturally cross-pollinating relative of wheat, is a tertiary gene donor and of substantial value in wheat improvement. Wheat powdery mildew is caused by Blumeria graminis f. sp. tritici (Bgt), which seriously affects yield and quality worldwide. Identifying and transferring new, effective resistance genes against powdery mildew from rye is important for wheat breeding. The current study developed a wheat-rye line YT2 resistant to powdery mildew by crossing, backcrossing, and self-pollination for multiple generations between octoploid triticale 09R2-100 and common wheat cultivar Shixin 616. YT2 was confirmed to be a 6R disomic addition and T1RS⋅1BL translocation line by genomic in situ hybridization (GISH), multicolor fluorescence in situ hybridization (mc-FISH), multicolor-GISH (mc-GISH), and molecular marker analyses. Disease responses to different Bgt isolates and genetic analysis showed that the powdery mildew resistance gene of YT2 was derived from the rye chromosome 6R of 09R2-100, which differed from the previously reported Pm genes from rye including Pm20 on 6RL. Resistance phenotype of different translocation lines and deletion lines derived from YT2 combined with newly developed 6RL-specific markers analysis suggested that the powdery mildew resistance gene of YT2 was localized to the region in chromosome 6RL: 890.09-967.51 Mb and flanked by markers XM189 and X4M19, corresponding to the reference genome of Weining rye. Therefore, YT2 could be used as a promising bridging parent for wheat disease resistance improvement.

Phosphorus-Induced Adaptation Mechanisms of Rye Grown on Post-Flotation Copper Tailings

Simple Summary

The mining activities for the production of copper, lead, zinc, and others are inevitably associated with the generation of an enormous volume of waste materials, i.e., tailings. The global area covered with tailings is on the order of hundreds of millions of hectares, with this being predicted to rise significantly in the coming decades. Importantly, the physicochemical properties of tailings, such as high content of heavy metals and high pH, pose a serious threat to the surrounding ecological environment. This, combined with low available nutrients, makes revegetation of degraded lands very difficult, with the number of field trials demonstrating successful revitalisation remaining very low. In this study, we investigate in rye, as a model plant, a wide array of physiological processes and their significance in determining survival on the copper tailings. We demonstrate that limitations in plant growth on such wastes is not simply related to high copper content. Rather, we present data that the low availability of phosphorus and activity of the mechanisms involved in phosphorus extraction from the rhizosphere are important determinants of the plant growth and survival rate. With these results, we make a direct and significant contribution towards meeting future demands for effective revitalisation techniques of degraded lands.

Abstract

Although a considerable effort has been made over the last decades to develop cost-effective phytotechnologies as an alternative to conventional techniques for the management of contaminated lands, successful revegetation of the tailings still represents a major challenge. Here, we evaluate the potential of rye (Secale cereale L.) for growth and survival on the tailings after copper (Cu) ore processing. Four rye varieties were cultivated in a pot experiment on the post-flotation sediment with increasing phosphorus (P) doses (22, 44, 66, 88, and 110 mg·kg⁻¹). The resistance of the studied rye genotypes to stress was assessed by observing the growth and development of plants, determining the dry mass accumulation, the Cu and P uptake and content, and a number of physiological parameters related mainly to P mobilisation. Exposure of tested rye varieties to high Cu concentrations in the tailings did not result in any significant plant mortality, with the intracellular Cu concentrations being below the critical toxic level. In contrast, the low availability of P due to alkaline properties of the tailings and the mechanisms involved in the mobilisation of sparingly soluble forms of this element (i.e., H⁺-ATPase-driven proton efflux in roots and organic acid exudation), were identified as main factor determining the level of tolerance. The efficiency of the photosynthetic activity was a key determinant for the P-mobilising capacity of rye. We further showed that rye varieties with more primitive genetic background might be potentially more suitable for growth on the post-flotation copper tailings. The results provide important and novel knowledge that will certainly support future works in developing strategies for successful revitalisation of degraded lands.

Harnessing translational research in wheat for climate resilience

Despite being the world's most widely grown crop, research investments in wheat (Triticum aestivum and Triticum durum) fall behind those in other staple crops. Current yield gains will not meet 2050 needs, and climate stresses compound this challenge. However, there is good evidence that heat and drought resilience can be boosted through translating promising ideas into novel breeding technologies using powerful new tools in genetics and remote sensing, for example. Such technologies can also be applied to identify climate resilience traits from among the vast and largely untapped reserve of wheat genetic resources in collections worldwide. This review describes multi-pronged research opportunities at the focus of the Heat and Drought Wheat Improvement Consortium (coordinated by CIMMYT), which together create a pipeline to boost heat and drought resilience, specifically: improving crop design targets using big data approaches; developing phenomic tools for field-based screening and research; applying genomic technologies to elucidate the bases of climate resilience traits; and applying these outputs in developing next-generation breeding methods. The global impact of these outputs will be validated through the International Wheat Improvement Network, a global germplasm development and testing system that contributes key productivity traits to approximately half of the global wheat-growing area.

Wheat root systems as a breeding target for climate resilience

In the coming decades, larger genetic gains in yield will be necessary to meet projected demand, and this must be achieved despite the destabilizing impacts of climate change on crop production. The root systems of crops capture the water and nutrients needed to support crop growth, and improved root systems tailored to the challenges of specific agricultural environments could improve climate resiliency. Each component of root initiation, growth and development is controlled genetically and responds to the environment, which translates to a complex quantitative system to navigate for the breeder, but also a world of opportunity given the right tools. In this review, we argue that it is important to know more about the 'hidden half' of crop plants and hypothesize that crop improvement could be further enhanced using approaches that directly target selection for root system architecture. To explore these issues, we focus predominantly on bread wheat (Triticum aestivum L.), a staple crop that plays a major role in underpinning global food security. We review the tools available for root phenotyping under controlled and field conditions and the use of these platforms alongside modern genetics and genomics resources to dissect the genetic architecture controlling the wheat root system. To contextualize these advances for applied wheat breeding, we explore questions surrounding which root system architectures should be selected for, which agricultural environments and genetic trait configurations of breeding populations are these best suited to, and how might direct selection for these root ideotypes be implemented in practice.

Structural rearrangements in wheat (1BS)-rye (1RS) recombinant chromosomes affect gene dosage and root length

Good understanding of the genes controlling root development is required to engineer root systems better adapted to different soil types. In wheat (Triticum aestivum L.), the 1RS.1BL wheat-rye (Secale cereale L.) translocation has been associated with improved drought tolerance and a large root system. However, an isogenic line carrying an interstitial segment from wheat chromosome arm 1BS in the distal region of the 1RS arm (1RS^RW ) showed reduced grain yield and shorter roots both in the field and in hydroponic cultures relative to isogenic lines with the complete 1RS arm. In this study, we used exome capture to characterize 1RS^RW and its parental lines T-9 and 1B+40. We show that 1RS^RW has a 7.0 Mb duplicated 1RS region and a 4.8 Mb 1BS insertion colinear with the 1RS duplication, resulting in triplicated genes. Lines homozygous for 1RS^RW have short seminal roots, while lines heterozygous for this chromosome have roots of intermediate length. By contrast, near-isogenic lines carrying only the 1BS distal region or the 1RS-1BS duplication have long seminal roots similar to 1RS, suggesting a limited effect of the 1BS genes. These results suggest that the dosage of duplicated 1RS genes is critical for seminal root length. An induced deletion encompassing 38 orthologous wheat and rye duplicated genes restored root length and confirmed the importance of gene dosage in the short-root phenotype. We explored the expression profiles and functional annotation of these genes and discuss their potential as candidate genes for the regulation of seminal root length in wheat.

Nutrient Digestibility of a Vegetarian Diet with or without the Supplementation of Feather Meal and Either Corn Meal, Fermented Rye or Rye and Its Effect on Fecal Quality in Dogs

Simple Summary

There is a particular need to find components for more sustainability in dog foods. Rye can be produced with a very low environmental impact among cereals. Animal products like hydrolyzed feather meal cannot be used for human consumption. The aim of the present study was to evaluate the offering of a vegetarian diet supplemented with or without feather meal and either corn meal, fermented rye or rye on the fecal quality and the digestibility of nutrients in dogs. Thus, eight Beagle dogs (11.0 ± 1.31 kg) with a median age of three years were included for this study. The dogs received a vegetarian basic diet containing wheat, broken rice and rice protein or the same diet supplemented with hydrolyzed feather meal (2.7%) and either 20.1% of corn meal, 60.4% of fermented rye or 20.1% of rye as is basis (moisture content of the diets about 42%). During the study, the feces were well formed and firm and the digestibility of the diet was not different by using rye compared to all other diets. Moreover, the acceptance “food intake scoring“ was similar among the experimental diets fed to dogs. Therefore, rye can be considered as an alternative cereal grain in dog foods.

Abstract

Cereals with low environmental input like rye and animal by-products which cannot be used for human food like feather meal are receiving growing interest as sustainable feed sources. Thus, eight Beagle dogs were included in a 4 × 4 Latin Square design and received a vegetarian basic diet or the same diets supplemented with hydrolyzed feather meal (2.7%) and either 20.1% of corn meal, 60.4% of fermented rye or 20.1% of rye as is basis (moisture content of the diets about 42%). Compared to other groups the dry matter (DM) content of feces from dogs fed the basic diet was higher (30.0%, p < 0.05), while dogs fed the basic diet + rye had the lowest DM-content (26.5%, p < 0.05). However, the fecal scores were considered to be within an acceptable range (well-formed and firm). Starch digestibility was lower (p < 0.05) for dogs fed the basic diet + corn meal. The dogs showed a high and identical acceptance (scoring of food intake) of the experimental diets. As a comparable quality of feces and a high nutrient digestibility were observed when rye was used in the experimental diets—it can be considered an alternative carbohydrate source in dog foods.

Identification of an Elite Wheat-Rye T1RS·1BL Translocation Line Conferring High Resistance to Powdery Mildew and Stripe Rust

Wheat-rye T1RS·1BL translocations have been widely used worldwide in wheat production for multiple disease resistance and superior yield traits. However, many T1RS·1BL translocations have successively lost their resistance to pathogens due to the coevolution of pathogen virulence with host resistance. Because of the extensive variation in rye (Secale cereale L.) as a naturally cross-pollinating relative of wheat, it still has promise to widen the variation of 1RS and to fully realize its application value in wheat improvement. In the present study, the wheat-rye breeding line R2207 was characterized by comprehensive analyses using genomic in situ hybridization (GISH), multicolor fluorescence in situ hybridization with multiple probes, multicolor GISH, and molecular marker analysis, and then was proven to be a cytogenetically stable wheat-rye T1RS·1BL translocation line. Based on the disease responses to different isolates of powdery mildew and genetic analysis, R2207 appears to possess a novel variation for resistance, which was confirmed to be located on the rye chromosome arm 1RS. Line R2207 also exhibited high levels of resistance to stripe rust at both seedling and adult stages, as well as enhanced agronomic performance, so it has been transferred into a large number of commercial cultivars using an efficient 1RS-specific kompetitive allele specific PCR marker for marker-assisted selection.