Stem Solidness Research Articles

A large-scale multiomics analysis of wheat stem solidness and the wheat stem sawfly feeding response, and syntenic associations in barley, Brachypodium, and rice

The wheat stem sawfly (WSS), Cephus cinctus Norton (Hymenoptera: Cephidae), is an important pest of wheat and other cereals, threatening the quality and quantity of grain production. WSS larvae feed and develop inside the stem where they are protected from the external environment; therefore, pest management strategies primarily rely on host plant resistance. A major locus on the long arm of wheat chromosome 3B underlies most of the variation in stem solidness; however, the impact of stem solidness on WSS feeding has not been completely characterized. Here, we used a multiomics approach to examine the response to WSS in both solid- and semi-solid-stemmed wheat varieties. The combined transcriptomic, proteomic, and metabolomic data revealed that two important molecular pathways, phenylpropanoid and phosphate pentose, are involved in plant defense against WSS. We also detected a general downregulation of several key defense transcripts, including those encoding secondary metabolites such as DIMBOA, tricetin, and lignin, which suggested that the WSS larva might interfere with plant defense. We comparatively analyzed the stem solidness genomic region known to be associated with WSS tolerance in wild emmer, durum, and bread wheats, and described syntenic regions in the close relatives barley, Brachypodium, and rice. Additionally, microRNAs identified from the same genomic region revealed potential regulatory pathways associated with the WSS response. We propose a model outlining the molecular responses of the WSS–wheat interactions. These findings provide insight into the link between stem solidness and WSS feeding at the molecular level.

Characterization of Resistance to Cephus cinctus (Hymenoptera: Cephidae) in Barley Germplasm.

Most barley cultivars have some degree of resistance to the wheat stem sawfly (WSS), Cephus cinctus Norton (Hymenoptera: Cephidae). Damage caused by WSS is currently observed in fields of barley grown in the Northern Great Plains, but the impact of WSS damage among cultivars due to genetic differences within the barley germplasm is not known. Specifically, little is known about the mechanisms underlying WSS resistance in barley. We characterized WSS resistance in a subset of the spring barley CAP (Coordinated Agricultural Project) germplasm panel containing 193 current and historically important breeding lines from six North American breeding programs. Panel lines were grown in WSS infested fields for two consecutive years. Lines were characterized for stem solidness, stem cutting, WSS infestation (antixenosis), larval mortality (antibiosis), and parasitism (indirect plant defense). Variation in resistance to WSS in barley was compared to observations made for solid-stemmed resistant and hollow-stemmed susceptible wheat lines. Results indicate that both antibiosis and antixenosis are involved in the resistance of barley to the WSS, but antibiosis seems to be more prevalent. Almost all of the barley lines had greater larval mortality than the hollow-stemmed wheat lines, and only a few barley lines had mortality as low as that observed in the solid-stemmed wheat line. Since barley lines lack solid stems, it is apparent that barley has a different form of antibiosis. Our results provide information for use of barley in rotation to control the WSS and may provide a basis for identification of new approaches for improving WSS resistance in wheat.

Identification of Candidate Genes Responsible for Stem Pith Production Using Expression Analysis in Solid-Stemmed Wheat.

The wheat stem sawfly (WSS) is an economically important pest of wheat in the Northern Great Plains. The primary means of WSS control is resistance associated with the single quantitative trait locus (QTL) , which controls most stem solidness variation. The goal of this study was to identify stem solidness candidate genes via RNA-seq. This study made use of 28 single nucleotide polymorphism (SNP) makers derived from expressed sequence tags (ESTs) linked to contained within a 5.13 cM region. Allele specific expression of EST markers was examined in stem tissue for solid and hollow-stemmed pairs of two spring wheat near isogenic lines (NILs) differing for the QTL. Of the 28 ESTs, 13 were located within annotated genes and 10 had detectable stem expression. Annotated genes corresponding to four of the ESTs were differentially expressed between solid and hollow-stemmed NILs and represent possible stem solidness gene candidates. Further examination of the 5.13 cM region containing the 28 EST markers identified 260 annotated genes. Twenty of the 260 linked genes were up-regulated in hollow NIL stems, while only seven genes were up-regulated in solid NIL stems. An -methyltransferase within the region of interest was identified as a candidate based on differential expression between solid and hollow-stemmed NILs and putative function. Further study of these candidate genes may lead to the identification of the gene(s) controlling stem solidness and an increased ability to select for wheat stem solidness and manage WSS.

Influence of Stem Solidness on Stem Strength and Stem Solidness Associated QTLs in Bread Wheat

Influence of Stem Solidness on Stem Strength and Stem Solidness Associated QTLs in Bread Wheat

The mineralization effect of wheat straw on soil properties described by MFPC analysis and other methods

Abstract Recycling of crop residues is essential to sustain soil fertility and crop production. Despite the positive effect of straw incorporation, the slow decomposition of that organic substance is a serious issue. The aim of the study was to assess the influence of winter wheat straws with different degrees of stem solidness on the rate of decomposition and soil properties. An incubation experiment lasting 425 days was carried out in controlled conditions. To perform analyses, soil samples were collected after 7, 14, 21, 28, 35, 49, 63, 77, 91, 119, 147, 175, 203, 231, 259, 313, 341, 369, 397 and 425 days of incubation. The addition of two types of winter wheat straw with different degree of stem solidness into the sandy soil differentiated the experimental treatments. The results demonstrate that straw mineralization was a relatively slow process and did not depend on the degree of filling of the stem by pith. Multivariate functional principal component analysis (MFPC) gave proof of significant variation between the control soil and the soil incubated with the straws. The first functional principal component describes 48.53% and the second 18.55%, of the variability of soil properties. Organic carbon, mineral nitrogen and sum of bases impact on the first functional principal component, whereas, magnesium, sum of bases and total nitrogen impact on the second functional principal component.

Host plant quantitative trait loci affect specific behavioral sequences in oviposition by a stem-mining insect.

Genetic diversity in quantitative loci associated with plant traits used by insects as cues for host selection can influence oviposition behavior and maternal choice. Host plant selection for oviposition is an important determinant of progeny performance and survival for phytophagous insects. Specific cues from the plant influence insect oviposition behavior; but, to date, no set of host plant quantitative trait loci (QTLs) have been shown to have an effect on behavioral sequences leading to oviposition. Three QTLs in wheat (Triticum aestivum L.) have been identified as influencing resistance to the wheat stem sawfly (WSS) (Cephus cinctus Norton). Wheat near-isogenic lines (NILs) for each of the three QTLs were used to test whether foraging WSS were able to discriminate variation in plant cues resulting from allelic changes. A QTL on chromosome 3B (Qss-msub-3BL) previously associated with stem solidness and larval antibiosis was shown to affect WSS oviposition behavior, host preference, and field infestation. Decreased preference for oviposition was also related to a QTL allele on chromosome 2D (Qwss.msub-2D). A QTL on chromosome 4A (Qwss.msub-4A.1) affected host plant attractiveness to foraging females, but did not change oviposition preference after females landed on the stem. These findings show that oviposition decisions regarding potential plant hosts require WSS females to discriminate signals from the plant associated with allelic variation at host plant quantitative loci. Allele types in a host plant QTL associated with differential survival of immature progeny can affect maternal choices for oviposition. The multidisciplinary approach used here may lead to the identification of plant genes with important community consequences, and may complement the use of antibiosis due to solid stems to control the wheat stem sawfly in agroecosystems.

Alleles at a quantitative trait locus for stem solidness in wheat affect temporal patterns of pith expression and level of resistance to the wheat stem sawfly

AbstractThe stem solidness trait in wheat has been the most effective mechanism for management of the wheat stem sawfly (WSS) for six decades. However, recent results have shown that in certain genotypes, the degree of stem solidness is not a useful indicator of WSS resistance. A morphological characterization of solidness expression indicated that in the genotype ‘Conan’, very solid pith undergoes rapid retraction during stem maturation, resulting in significantly less solidness at maturity. In other solid‐stemmed genotypes, including the standard WSS‐resistant cultivar ‘Choteau’, dense pith in the stem remains nearly unchanged throughout plant development. In cage trials, ‘Conan’ plants were less preferred for oviposition by the WSS when paired with ‘Choteau’ plants. Field bioassays using near‐isogenic lines differing for alleles at Qss.msub‐3BL showed that the Conan allele provides higher levels of early stem solidness and rapid pith retraction during stem maturation. These results suggest that the traditional approach for increasing WSS resistance by selecting for increasing stem solidness needs to be modified to consider temporal variations in pith expression associated with alleles at Qss.msub‐3BL.

Sowing Density and Cultivar Effects on Pith Expression in Solid‐Stemmed Durum Wheat

The wheat stem sawfly (WSS) (Cephus cinctus; Hymenoptera: Cephidae) is a destructive insect pest of spring, winter (Triticum aestivum L.), and durum wheat (Triticum turgidum L. var. durum) in North America. Sawfly larvae hatch from eggs deposited inside the stem, and their subsequent feeding damages vascular tissue, reducing photosynthetic capacity and grain yields. Growing solid‐stemmed wheat cultivars that develop pith in the culm lumen is the most effective method to minimize yield losses. Recent work has focused on optimizing sowing densities to achieve maximum levels of pith expression and grain yields in common wheat; however, little research has been conducted on durum wheat. We investigated the influence of four sowing densities (150, 250, 350, 450 seeds m−2) on pith expression in two newly released solid‐stemmed durum cultivars, CDC Fortitude and AAC Raymore, and compared them to the solid‐stemmed common wheat cultivar, Lillian. CDC Fortitude and AAC Raymore displayed consistently high levels of pith expression across environments and sowing densities, in contrast to Lillian, which produced only slightly more pith than the hollow‐stemmed durum check cultivar, Strongfield. A yield drag often associated with high pith expression was not evident as CDC Fortitude and AAC Raymore produced grain yield similar to Strongfield. When averaged over cultivars, increasing sowing density had a positive effect on grain yield, but was negatively associated with stem solidness. Our findings suggest that, unlike with CWRS solid‐stemmed cultivars, altering sowing density is not required to achieve effective sawfly resistance with CDC Fortitude and AAC Raymore.

Association Analysis of Stem Solidness and Wheat Stem Sawfly Resistance in a Panel of North American Spring Wheat Germplasm

ABSTRACTThe expanding geographical range of wheat stem sawfly (WSS) damage, coupled with the limited number of effective control measures, calls for a need to better characterize and explore the genetic variability for resistance in wheat (Triticum aestivum L.) germplasm from North America. An association‐mapping analysis for stem solidness and wheat stem sawfly resistance was conducted using a set of 244 elite spring wheat lines from 10 North American breeding programs. Three previously identified quantitative trait loci (QTL) for resistance were confirmed, including QTL for stem solidness, heading date, and stem cutting. Three new QTL on chromosomes 2A, 3A, and 5B were identified to be associated with larval mortality and a QTL associated with early stem solidness was identified on chromosome 5D. Genetic variation for late stem solidness is mainly determined by the solid‐stem QTL on chromosome 3B, while variation for early solidness is affected by chromosomal regions on 1B, 3B, and 5D. Potential sources of a novel resistance mechanism causing larval mortality were identified among the panel lines. Favorable alleles for stem solidness and other resistance traits are available within North American wheat germplasm, but only Montana and South Dakota breeding programs appear to have favorable alleles for all QTLs detected in this study. Improvements in wheat stem sawfly management, for both historically impacted areas and for regions first experiencing damage, may be obtained using alleles that already exist in elite germplasm.

A Multiple Decrement Life Table Reveals That Host Plant Resistance and Parasitism Are Major Causes of Mortality for the Wheat Stem Sawfly.

This study investigated the dynamics of parasitism, host plant resistance, pathogens, and predation on the demography of wheat stem sawfly, Cephus cinctus Norton (Hymenoptera: Cephidae), developing in susceptible (hollow stem) and resistant (solid stem) wheat hosts. This study is also the first to investigate the prevalence and impact of cannibalism on wheat stem sawfly mortality. Wheat stem sawflies were sampled in two commercial wheat fields over 4 yr from the egg stage through adult emergence, and multiple decrement life tables were constructed and analyzed. Cannibalism, host plant resistance, or unknown factors were the most prevalent factors causing egg mortality. Summer mortality of prediapause larvae ranged from 28 to 84%, mainly due to parasitism by Bracon cephi (Gahan) and Bracon lissogaster Muesebeck, cannibalism, and host plant resistance. Winter mortality ranged from 6 to 54% of the overwintering larvae, mainly due to unknown factors or pathogens. Cannibalism is a major cause of irreplaceable mortality because it is absolute, with only a single survivor in every multiple infested stem. Subsequent to obligate cannibalism, mortality of feeding larvae due to host plant resistance was lower in hollow stem wheat than in solid stem wheat. Mortality from host plant resistance was largely irreplaceable. Irreplaceable mortality due to parasitoids was greater in hollow stem wheat than in solid stem wheat. Host plant resistance due to stem solidness and parasitism in hollow stems cause substantial mortality in populations of actively feeding larvae responsible for all crop losses. Therefore, enhancing these mortality factors is vital to effective integrated pest management of wheat stem sawfly.

Impact of the D genome and quantitative trait loci on quantitative traits in a spring durum by spring bread wheat cross.

The impact of the D genome and QTL in the A and B genomes on agronomic performance of hexaploid wheat and tetraploid durum was determined using novel recombinant inbred line populations derived from interploid crosses. Genetic differences between common hexaploid (6X) bread wheat (Triticum aestivum, 2n = 6x = 42, genome, AABBDD) and tetraploid (4X) durum wheat (T. turgidum subsp. durum, 2n = 4x = 28, genome, AABB) may exist due to effects of the D genome and allelic differences at loci in the A and B genomes. Previous work allowed identification of a 6X by 4X cross combination that resulted in a large number of fertile recombinant progeny at both ploidy levels. In this study, interspecific recombinant inbred line populations at both 4X and 6X ploidy with 88 and 117 individuals, respectively, were developed from a cross between Choteau spring wheat (6X) and Mountrail durum wheat (4X). The presence of the D genome in the 6X population resulted in increased yield, tiller number, kernel weight, and kernel size, as well as a decrease in stem solidness, test weight and seed per spike. Similar results were found with a second RIL population containing 152 lines from 18 additional 6X by 4X crosses. Several QTL for agronomic and quality traits were identified in both the 4X and 6X populations. Although negatively impacted by the lack of the D genome, kernel weight in Mountrail (4X) was higher than Choteau (6X) due to positive alleles from Mountrail on chromosomes 3B and 7A. These and other favorable alleles may be useful for introgression between ploidy levels.

Agronomic Impact of a Stem Solidness Gene in Near‐Isogenic Lines of Wheat

ABSTRACTThe primary trait in wheat (Triticum aestivum L.) to prevent damage caused by the wheat stem sawfly (WSS) (Cephus cinctus) is antibiosis facilitated by solid stems. The pith of solid stems impedes development of larvae, often resulting in their death inside the stem. A key question regarding solid stems is the possible impact on grain yield potential due to photosynthate partitioning to stem pith instead of to grain. Molecular markers for the major gene controlling stem solidness, Qss.msub‐3BL, were used to develop near‐isogenic lines (NIL) for alleles at Qss.msub‐3BL in six genetic backgrounds. The NIL were grown in replicated trials in 12 locations that varied for yield potential in Montana, Washington, and Idaho. There was no significant impact of the solid stem allele on grain yield based on mean performance over recurrent parents and locations. Individually, solid‐stemmed NIL were significantly lower yielding in one of six genetic backgrounds. Based on means over all crosses, the solid‐stemmed NIL had lower yield in only one high‐yielding environment. These results suggest that in general the allele for solid stems at Qss.msub‐3BL does not result in yield reduction. Development of solid‐stemmed cultivars with yield potential similar to the best hollow‐stemmed cultivars is a reasonable goal for wheat breeding programs in areas impacted by the WSS.

Registration of ‘Warhorse’ Wheat

‘Warhorse’ (Reg. No. CV-1096, PI 670157) hard red winter (HRW) wheat (Triticum aestivum L.) was developed and released by the Montana Agricultural Experiment Station in September 2013. Warhorse is of unknown pedigree, derived from a composite of three topcrosses made to the same F 1 population in 2000: MT9908//‘Nuplains’/MTS9862; Nuplains/ MTS9862//MTW0047; and Nuplains/MTS9862//MTS0028. Warhorse was developed using a modified bulk breeding method and selected as an F 5:6 headrow. Warhorse was tested under the experimental number MTS0808 from 2008 to 2013 in Montana. Quality was evaluated in multilocation Montana trials since 2008. Warhorse is a solid-stem, high-yielding HRW wheat line with medium to high test weight, medium maturity, reduced height (Rht-B1b), medium to high grain protein, and acceptable milling and baking quality. Warhorse was released for its improved host plant resistance to wheat stem sawfly (Cephus cinctus Nort.) conditioned by stem solidness, along with short stature and improved yield potential relative to existing solid-stem cultivars adapted to Montana.

Resistance to Cephus cinctus Norton, the wheat stem sawfly, in a recombinant inbred line population of wheat derived from two resistance sources

AbstractSeveral species of wheat stem sawflies (WSS) are pests of wheat, including Cephus cinctus Norton in North America. Larvae feed inside the stems and cut the stem near plant maturity. The primary means of control is resistance due to solid stems, largely controlled by a locus on chromosome 3B (Qss.msub‐3BL). Cultivars that differed for WSS resistance, but with similar stem solidness, were crossed to determine the genetic basis for the differences. The cultivar ‘Scholar’ is susceptible, while ‘Conan’ shows resistance. Scholar and Conan possessed different alleles at Qss.msub‐3BL. Both alleles conferred solidness, yet the Conan allele conferred higher WSS resistance. An allele from Conan on chromosome 4A also decreased infestation and stem cutting. The 3B and 4A alleles from Conan acted in an additive fashion to provide increased WSS resistance without increasing stem solidness. Stem solidness has long been used by breeders as a proxy for WSS resistance because of its simplicity. Our results suggest that other resistance mechanisms may complement solid stems.

Application of molecular markers to wheat breeding in Canada

AbstractMarker‐assisted breeding provides an opportunity for wheat breeders to introgress/pyramid genes of interest into breeding lines and to identify genes and/or quantitative trait loci in germplasm to be used as parents. Molecular markers were deployed to assist selection for disease resistance, agronomic and quality traits in several wheat cultivars released for commercial cultivation in Canada. Marker‐assisted breeding is routinely used in most wheat breeding programmes for rust resistance (leaf, stem and stripe rust), orange wheat blossom midge resistance, high grain protein concentration, Fusarium head blight and common bunt resistance. Markers are being used selectively within breeding programmes to target traits that relate to market class or regional adaptation. For example, marker‐assisted breeding for low lipoxygenase activity and low grain cadmium is being performed in durum breeding programmes and for enhancing stem solidness in programmes targeting resistance to the wheat stem sawfly. Markers are also being utilized for ergot resistance in durum wheat. Increased gluten strength is being selected with a marker for the overexpression of the Bx7 high‐molecular‐weight glutenin subunit. Marker‐assisted breeding is also being used to pyramid resistance genes against a group of stem rust races related to TTKS (Ug99), a disease that poses a serious threat to global wheat production. Development of tightly linked diagnostic markers and high‐throughput genotyping with SNP markers will result in more effective molecular wheat breeding in the near future and will open the door to genomic selection.

Registration of ‘Bearpaw’ Wheat

‘Bearpaw’ (Reg. No. CV‐1083, PI 665228) hard red winter (HRW) wheat (Triticum aestivum L.) was developed and released by the Montana Agricultural Experiment Station in September 2011. Bearpaw is of unknown pedigree, derived from a composite of five crosses made to the same F1 male sterile parent in 1999: Dominant male sterile (DMS)/‘Rampart’//‘Pronghorn’/3/2*Rampart, DMS/Rampart//Pronghorn/3/Rampart/4/MTW9806, DMS/Rampart//Pronghorn/3/Rampart/4/‘Nuplains’, DMS/Rampart//Pronghorn/3/Rampart/4/MT9513, DMS/Rampart//Pronghorn/3/Rampart/4/MT98113. Bearpaw was developed using a modified bulk‐breeding method and selected as an F5:6 headrow. Bearpaw was tested under the experimental number MTS0721 from 2007 to 2011 in Montana. Quality has been evaluated in multilocation Montana trials since 2007. Bearpaw is a high‐yielding, solid‐stem, semidwarf (Rht‐B1b) HRW wheat cultivar with medium maturity, medium to high test weight and grain protein, and acceptable milling and baking quality. Bearpaw was released for its host‐plant resistance to wheat stem sawfly (Cephus cinctus Nort.) conditioned by stem solidness, along with short stature and improved yield potential relative to existing solid‐stem cultivars adapted to Montana.

Registration of ‘Judee’ Wheat

‘Judee’ (Reg. No. CV‐1084, PI 665227) hard red winter (HRW) wheat (Triticum aestivum L.) was developed and released by the Montana Agricultural Experiment Station in September 2011. Judee has the pedigree ‘Vanguard’/‘Norstar’//‘Judith’ dwarf selection/3/‘NuHorizon’. Judee was developed using a modified bulk‐breeding method and selected as an F5:6 headrow. Judee was tested under the experimental number MTS0713 from 2007 to 2011 in Montana. Quality was evaluated in multilocation Montana trials since 2007. Judee is a solid‐stem, high‐yielding HRW wheat line with medium to high test weight, medium maturity, reduced height (Rht‐B1b), medium to high grain protein, and acceptable milling and baking quality. Judee was released for its host‐plant resistance to wheat stem sawfly (Cephus cinctus Nort.) conditioned by stem solidness, along with short stature and improved yield potential relative to existing solid‐stem cultivars adapted to Montana.

Influence of Seeding Rate, Nitrogen Management, and Micronutrient Blend Applications on Pith Expression in Solid‐Stemmed Spring Wheat

ABSTRACTThe wheat stem sawfly (Cephus cinctus Norton [Hymenoptera: Cephidae]) is a serious threat to wheat (Triticum aestivum L.) and other cereal grains in the northern Great Plains. Wheat cultivars with high expression of pith in the culm of the stem (stem solidity) can minimize losses associated with sawfly infestations and subsequent stem boring of the larva. Based on the widespread area now sown to solid‐stemmed wheat, our objective was to develop an integrated nutrient and planting strategy specific to solid‐stemmed spring wheat using modern farming techniques. Five levels of banded N fertilizer (0, 30, 60, 90, and 120 kg N ha−1) were arranged in a factorial combination with three levels of sowing density (100, 300, and 500 seeds m−2) and grown at three sites in southern Alberta, Canada, from 2007 to 2009. Increased planting densities optimized yield, but an inverse relationship with pith expression (stem solidness) was observed. Low plant populations (100 seeds m−2) were often most effective at maximizing pith expression in solid‐stemmed wheat and reducing sawfly cutting damage. However, this usually required the highest rates of N fertilizer, so a system of low seeding rates and high N may not be economical based on fertilizer input costs and the generally lower grain yield response (−9%). An integrated planting and nutrient strategy for solid‐stemmed spring wheat cultivars consists of seeding rates no greater than 300 seeds m−2 and basal N applications in the range of 30 to 60 kg N ha−1.

Marker-assisted characterization of durum wheat Langdon–Golden Ball disomic substitution lines

The durum wheat cultivar 'Golden Ball' (GB) is a source of resistance to wheat sawfly due to its superior solid stem. In the late 1980s, Dr. Leonard Joppa developed a complete set of 14 'Langdon' (LDN)-GB disomic substitution (DS) lines by using GB as the chromosome donor and LDN as the recipient. However, these substitution lines have not been previously characterized and reported in the literature. The objectives of this study were to confirm the authenticity of the substituted chromosomes and to analyze the genetic background of the 14 LDN-GB DS lines with the aid of molecular markers, and to further use the substitution lines for chromosomal localization of DNA markers and genes conferring the superior stem solidness in GB. Results from simple sequence repeat marker analysis validated the authenticity of the substituted chromosomes in 14 LDN-GB DS lines. Genome-wide scans using the target region amplification polymorphism (TRAP) marker system produced a total of 359 polymorphic fragments that were used to compare the genetic background of substitution lines with that of LDN. Among the polymorphic TRAP markers, 134 (37.3%) and 185 (51.5%) were present in LDN and GB, respectively, with only 10 (2.8%) derived from Chinese Spring. Therefore, marker analysis demonstrated that each LDN-GB DS line had a pair of chromosomes from GB with a genetic background similar to that of LDN. Of the TRAP markers generated in this study, 200 were successfully assigned to specific chromosomes based on their presence or absence in the corresponding LDN-GB DS lines. Also, evaluation of stem solidness in the substitution lines verified the presence of a major gene for stem solidness in chromosome 3B. Results from this research provides useful information for the utilization of GB and LDN-GB DS lines for genetic and genomic studies in tetraploid wheat and for the improvement of stem solidness in both durum and bread wheat.

Stem solidness and its relationship to water-soluble carbohydrates: association with wheat yield under water deficit

A study of 36 wheat (Triticum aestivum L.) genotypes with different levels of stem solidness was conducted to assess the heritability and relationship among stem morphological properties, stem water-soluble carbohydrates (WSC) storage capacity and grain yield. The total amount of pith-fill in the upper stem internode (VOL) was highly correlated with the total content of WSC per stem under both water deficit (DEF) (r = 0.56) and well irrigated conditions (IRR) (r = 0.49). A positive correlation was also found between VOL and grain yield under DEF (r = 0.49), which was explained by the positive contribution of WSC to grain yield. A closer association of grain yield and morphological traits was identified under DEF than under IRR. The closer associations found among estimations of %WSC and WSC-area and grain yield under DEF indicate that these variables may be adaptive rather than constitutive traits. High heritability values (0.77–0.84) observed for stem morphological traits reinforce their potential use in breeding for high WSC and ultimately, higher grain yield under water-limited environments. Stem length, diameter and solidness could be combined in an ideal plant ideotype to maximise WSC reserves as a strategy to improve yield under water-limited conditions.