Genome-wide association studies of agronomic and quality traits in a set of German winter barley (Hordeum vulgare L.) cultivars using Diversity Arrays Technology (DArT)

A set of about 100 winter barley (Hordeum vulgare L.) cultivars, comprising diverse and economically important German barley elite germplasm released during the last six decades, was previously genotypically characterized by single nucleotide polymorphism (SNP) markers using the Illumina GoldenGate BeadArray Technology to detect associations with phenotypic data estimated in three-year field trials at 12 locations. In order to identify further associations and to obtain information on whether the marker type influences the outcome of association genetics studies, the set of winter barley cultivars was re-analyzed using Diversity Arrays Technology (DArT) markers. As with the analysis of the SNPs, only polymorphic markers present at an allele frequency >5 % were included to detect associations in a mixed linear model (MLM) approach using the TASSEL software (P?≤?0.001). The population structure and kinship matrix were estimated on 72 simple sequence repeats (SSRs) covering the whole barley genome. The respective average linkage disequilibrium (LD) analyzed with DArT markers was estimated at 5.73 cM. A total of 52 markers gave significant associations with at least one of the traits estimated which, therefore, may be suitable for marker-assisted breeding. In addition, by comparing the results to those generated using the Illumina GoldenGate BeadArray Technology, it turned out that a different number of associations for respective traits is detected, depending on the marker system. However, as only a few of the respective DArT and Illumina markers are present in a common map, no comprehensive comparison of the detected associations was feasible, but some were probably detected in the same chromosomal regions. Because of the identification of additional marker–trait associations, it may be recommended to use both marker techniques in genome-wide association studies.     

Carbon footprint of spring barley in relation to preceding oilseeds and N fertilization

Purpose

Carbon footprint of field crops can be lowered through improved cropping practices. The objective of this study was to determine the carbon footprint of spring barley (Hordeum vulgare L.) in relation to various preceding oilseed crops that were fertilized at various rates of inorganic N the previous years. System boundary was from cradle-to-farm gate.

Materials and methods

Canola-quality mustard (Brassica juncea L.), canola (Brassica napus L.), sunflower (Helianthus annuus L.), and flax (Linum usitatissimum L.) were grown under the N fertilizer rates of 10, 30, 70, 90, 110, 150, and 200?kg?N?ha^?1 the previous year, and spring barley was grown on the field of standing oilseed stubble the following year. The study was conducted at six environmental sites; they were at Indian Head in 2005, 2006 and 2007, and at Swift Current in 2004, 2005 and 2006, Saskatchewan, Canada.

Results and discussion

On average, barley grown at humid Indian Head emitted greenhouse gases (GHGs) of 1,003?kg?CO₂eq?ha^?1, or 53% greater than that at the drier Swift Current site. Production and delivery of fertilizer N to farm gate accounted for 26% of the total GHG emissions, followed by direct and indirect emissions of 28% due to the application of N fertilizers to barley crop. Emissions due to N fertilization were 26.6 times the emission from the use of phosphorous, 5.2 times the emission from pesticides, and 4.2 times the emission from various farming operations. Decomposition of crop residues contributed emissions of 173?kg?CO₂eq?ha^?1, or 19% of the total emission. Indian Head-produced barley had significantly greater grain yield, resulting in about 11% lower carbon footprint than Swift Current-produced barley (0.28 vs. 0.32?kg?CO₂eq?kg^?1 of grain). Emissions in the barley production was a linear function of the rate of fertilizer N applied to the previous oilseed crops due to increased emissions from crop residue decomposition coupled with higher residual soil mineral N.

Conclusions

The key to lower the carbon footprint of barley is to increase grain yield, make a wise choice of crop types, reduce N inputs to crops grown in the previous and current growing seasons, and improved N use efficiency.     

Hybridisation‐based target enrichment of phenology genes to dissect the genetic basis of yield and adaptation in barley

Barley (Hordeum vulgare L.) is a major cereal grain widely used for livestock feed, brewing malts and human food. Grain yield is the most important breeding target for genetic improvement and largely depends on optimal timing of flowering. Little is known about the allelic diversity of genes that underlie flowering time in domesticated barley, the genetic changes that have occurred during breeding, and their impact on yield and adaptation. Here, we report a comprehensive genomic assessment of a worldwide collection of 895 barley accessions based on the targeted resequencing of phenology genes. A versatile target‐capture method was used to detect genome‐wide polymorphisms in a panel of 174 flowering time‐related genes, chosen based on prior knowledge from barley, rice and Arabidopsis thaliana. Association studies identified novel polymorphisms that accounted for observed phenotypic variation in phenology and grain yield, and explained improvements in adaptation as a result of historical breeding of Australian barley cultivars. We found that 50% of genetic variants associated with grain yield, and 67% of the plant height variation was also associated with phenology. The precise identification of favourable alleles provides a genomic basis to improve barley yield traits and to enhance adaptation for specific production areas.     

Comparison of the efficacy of chitosan with that of a fluorescent pseudomonad for the control of Fusarium head blight disease of cereals and associated mycotoxin contamination of grain

Fusarium culmorum can cause Fusarium head blight (FHB) disease of cereals, resulting in yield loss and contamination of grain with the trichothecene mycotoxin, deoxynivalenol (DON). In this study, we compared the efficacy of a biological control agent (Pseudomonas fluorescens strain MKB 158) with the biochemical chitosan (the deacetylated derivative of chitin) in controlling FHB disease of wheat and barley. Both agents were equally effective in reducing DON contamination of grain caused by F. culmorum. Under both glasshouse and field conditions, treatment with commercially available crabshell-derived chitosan reduced the severity of FHB symptom development on wheat and barley by ?74% (P ? 0.050). While treatment with P. fluorescens reduced the severity of FHB symptom development on these cereals by ?48% (P ? 0.050). Chitosan and P. fluorescens respectively prevented ?58 and ?35% of the FHB-associated reductions in 1000-grain weight in wheat and barley (P ? 0.050). Both agents significantly reduced the DON content of wheat and barley under both glasshouse and field conditions (P ? 0.050) and were equally efficacious in doing so (?74 and ?79% reductions due to chitosan and P. fluorescens, respectively). Crude chitin extracts from crabshells and crude chitosan-based formulations prepared from crabshells and eggshells were also tested under field conditions, but were not as effective as the commercial crabshell-derived preparation in controlling FHB disease. This is the first report on the use of chitosan for the control of Fusarium head blight disease and DON contamination of grain.     

QTLs for earliness and yield-forming traits in the Lubuski × CamB barley RIL population under various water regimes

Drought has become more frequent in Central Europe causing large losses in cereal yields, especially of spring crops. The development of new varieties with increased tolerance to drought is a key tool for improvement of agricultural productivity. Material for the study consisted of 100 barley recombinant inbred lines (RILs) (LCam) derived from the cross between Syrian and European parents. The RILs and parental genotypes were examined in greenhouse experiments under well-watered and water-deficit conditions. During vegetation the date of heading, yield and yield-related traits were measured. RIL population was genotyped with microsatellite and single nucleotide polymorphism markers. This population, together with two other populations, was the basis for the consensus map construction, which was used for identification of quantitative trait loci (QTLs) affecting the traits. The studied lines showed a large variability in heading date. It was noted that drought-treatment negatively affected the yield and its components, especially when applied at the flag leaf stage. In total, 60 QTLs were detected on all the barley chromosomes. The largest number of QTLs was found on chromosome 2H. The main QTL associated with heading, located on chromosome 2H (Q.HD.LC-2H), was identified at SNP marker 5880–2547, in the vicinity of Ppd-H1 gene. SNP 5880–2547 was also the closest marker to QTLs associated with plant architecture, spike morphology and grain yield. The present study showed that the earliness allele from the Syrian parent, as introduced into the genome of an European variety could result in an improvement of barley yield performance under drought conditions.     

Genomic regions associated with the nitrogen limitation response revealed in a global wheat core collection

Modern wheat (Triticum aestivum L.) varieties in Western Europe have mainly been bred, and selected in conditions where high levels of nitrogen-rich fertilizer are applied. However, high input crop management has greatly increased the risk of nitrates leaching into groundwater with negative impacts on the environment. To investigate wheat nitrogen tolerance characteristics that could be adapted to low input crop management, we supplied 196 accessions of a wheat core collection of old and modern cultivars with high or moderate amounts of nitrogen fertilizer in an experimental network consisting of three sites and 2 years. The main breeding traits were assessed including grain yield and grain protein content. The response to nitrogen level was estimated for grain yield and grain number per m² using both the difference and the ratio between performance at the two input levels and the slope of joint regression. A large variability was observed for all the traits studied and the response to nitrogen level. Whole genome association mapping was carried out using 899 molecular markers taking into account the five ancestral group structure of the collection. We identified 54 main regions involving almost all chromosomes that influence yield and its components, plant height, heading date and grain protein concentration. Twenty-three regions, including several genes, spread over 16 chromosomes were involved in the response to nitrogen level. These chromosomal regions may be good candidates to be used in breeding programs to improve the performance of wheat varieties at moderate nitrogen input levels.     

Effects of foliar application of BAP on source and sink strength in four six-rowed barley (Hordeum vulgare L.) cultivars

A field experiment was conducted to investigate the effects of foliar application of a synthetic cytokinin (BAP) on source and sink strength of four different six-rowed barley (Hordeum vulgare L.) cultivars. Different spraying treatments consisting of spraying on whole plant, spraying only on leaves and spraying only on ears started at anthesis and continued for 7 days. One additional spraying was carried out on late period of grain filling. Results showed that spraying only on leaves did not affect ear weight, grain yield and 1,000-grain weight, while the two other treatments increased all above mentioned traits. Neither of treatments affected stem weight, biological yield and contribution of stem reserves in grain filling. Exogenous cytokinin did not increase photosynthetic rate and chlorophyll content in treated leaves until late period of grain filling, although there was no significant increase in final grain weight due to late application of BAP. Our results suggested that effects of foliar application of BAP were mostly due to increased sink size soon after anthesis and increased sink demand probably met by current photosynthesis of organs other than leaves, like ear green tissues. An erratum to this article is available at .     

Mixed model association scans of multi-environmental trial data reveal major loci controlling yield and yield related traits in Hordeum vulgare in Mediterranean environments

An association panel consisting of 185 accessions representative of the barley germplasm cultivated in the Mediterranean basin was used to localise quantitative trait loci (QTL) controlling grain yield and yield related traits. The germplasm set was genotyped with 1,536 SNP markers and tested for associations with phenotypic data gathered over 2?years for a total of 24?year?×?location combinations under a broad range of environmental conditions. Analysis of multi-environmental trial (MET) data by fitting a mixed model with kinship estimates detected from two to seven QTL for the major components of yield including 1000 kernel weight, grains per spike and spikes per m², as well as heading date, harvest index and plant height. Several of the associations involved SNPs tightly linked to known major genes determining spike morphology in barley (vrs1 and int-c). Similarly, the largest QTL for heading date co-locates with SNPs linked with eam6, a major locus for heading date in barley for autumn sown conditions. Co-localization of several QTL related to yield components traits suggest that major developmental loci may be linked to most of the associations. This study highlights the potential of association genetics to identify genetic variants controlling complex traits.     

Root colonization by Piriformospora indica enhances grain yield in barley under diverse nutrient regimes by accelerating plant development

The basidiomycete fungus Piriformospora indica colonizes roots of a broad range of mono- and dicotyledonous plants. It confers enhanced growth, improves resistance against biotic and tolerance to abiotic stress, and enhances grain yield in barley. To analyze mechanisms underlying P. indica-induced improved grain yield in a crop plant, the influence of different soil nutrient levels and enhanced biotic stress were tested under outdoor conditions. Higher grain yield was induced by the fungus independent of different phosphate and nitrogen fertilization levels. In plants challenged with the root rot-causing fungus Fusarium graminearum, P. indica was able to induce a similar magnitude of yield increase as in unchallenged plants. In contrast to the arbuscular mycorrhiza fungus Glomus mosseae, total phosphate contents of host plant roots and shoots were not significantly affected by P. indica. On the other hand, barley plants colonised with the endophyte developed faster, and were characterized by a higher photosynthetic activity at low light intensities. Together with the increased root formation early in development these factors contribute to faster development of ears as well as the production of more tillers per plant. The results indicate that the positive effect of P. indica on grain yield is due to accelerated growth of barley plants early in development, while improved phosphate supply—a central mechanism of host plant fortification by arbuscular mycorrhizal fungi—was not observed in the P. indica-barley symbiosis.     

Response of Barley Genotypes to Fusarium Head Blight under Natural Infection and Artificial Inoculation Conditions

Forty-eight spring barley genotypes were evaluated for deoxynivalenol (DON) concentration under natural infection across 5 years at Harrington, Prince Edward Island. These genotypes were also evaluated for Fusarium head blight (FHB) severity and DON concentration under field nurseries with artificial inoculation of Fusarium graminearum by the grain spawn method across 2 years at Ottawa, Ontario, and one year at Hangzhou, China. Additionally, these genotypes were also evaluated for FHB severity under greenhouse conditions with artificial inoculation of F. graminearum by conidial suspension spray method across 3 years at Ottawa, Ontario. The objective of the study was to investigate if reactions of barley genotypes to artificial FHB inoculation correlate with reactions to natural FHB infection. DON concentration under natural infection was positively correlated with DON concentration (r = 0.47, P < 0.01) and FHB incidence (r = 0.56, P < 0.01) in the artificially inoculated nursery with grain spawn method. Therefore, the grain spawn method can be used to effectively screen for low DON. FHB severity, generated from greenhouse spray, however, was not correlated with DON concentration (r = 0.12, P > 0.05) under natural infection and it was not correlated with DON concentration (r = −0.23, P > 0.05) and FHB incidence (r = 0.19, P > 0.05) in the artificially inoculated nursery with grain spawn method. FHB severity, DON concentration, and yield were affected by year, genotype, and the genotype × year interaction. The effectiveness of greenhouse spray inoculation for indirect selection for low DON concentration requires further studies. Nine of the 48 genotypes were found to contain low DON under natural infection. Island barley had low DON and also had high yield.     

Mapping quantitative trait loci associated with spot blotch and net blotch resistance in a doubled-haploid barley population

Spot blotch and net blotch are important foliar barley (Hordeum vulgare L.) diseases in Canada and elsewhere. These diseases result in significant yield reduction and, more importantly, loss of grain quality, downgrading barley from malt to feed. Combining resistance to these diseases is a breeding priority but is a significant challenge using conventional breeding methodology. In the present investigation, an evaluation of the inheritance of resistance to spot and net blotch was conducted in a doubled-haploid barley population from the cross CDC Bold (susceptible)?×?TR251 (resistant). The population was screened at the seedling stage in the Phytotron and at the adult-plant stage in the field for several years. Chi-squared analysis indicated one- to four-gene segregation depending on disease, isolate, plant development stage, location and year. A major seedling and adult-plant resistance quantitative trait locus (QTL), designated QRpt6, was re-confirmed for net-form net blotch resistance, explaining 32?C61% of phenotypic variation in different experiments. Additional QTL for seedling and adult-plant resistance to net blotch were identified. For spot blotch resistance, a major seedling resistance QTL (QRcss1) was detected on chromosome 1H for isolate WRS1909, explaining 79% of the phenotypic variation. A highly significant QTL on 3H (QRcs3) was identified for seedling resistance to isolate WRS1908 and adult-plant resistance at Brandon, MB, Canada in 2008. The identification of QTL at only one location or from 1?year suggests spot blotch resistance is complex and highly influenced by the environment. Efforts are being made to combine spot and net blotch resistance in elite barley lines using molecular marker-assisted selection.     

Influence of barley grain particle size and treatment with citric acid on digestibility,ruminal fermentation and microbial protein synthesis in Holstein calves

Chemical and physical treatments of barley grain increase ruminally resistant starch and can improve the rumen fermentation pattern. The objective of the present study was to evaluate the effects of chemical (addition of citric acid, CA) and physical (grinding to two different particle sizes, PS) treatment of barley grain on performance, rumen fermentation, microbial protein yield in the rumen and selected blood metabolites in growing calves. In all, 28 male Holstein calves (172±5.1 kg initial BW) were used in a complete randomised design with a factorial arrangement of 2 barley grain particle sizes×2 levels of citric acid. The diets were as follows: (i) small PS (average 1200 µm) barley grain soaked in water (no CA addition); (ii) small PS barley grain soaked in a CA solution (adding 20 g CA/kg barley); (iii) large PS (average 2400 µm) barley grain soaked in water (no citric acid addition) and (iv) large PS barley grain soaked in a citric acid solution (adding 20 g CA/kg barley). Barley grain was then incorporated at 35% in a total mixed ration and fed to the calves for 11 weeks. Feeding small PS barley decreased feed intake (P=0.02) and average daily weight gain (P=0.01). The addition of CA to barley grain did not affect intake but increased weight gain (P<0.01) and improved feed to gain ratio (P=0.03). Digestibility of organic matter and NDF tended (P<0.10) to increase, whereas faecal scoring was improved (P=0.03) and the presence of undigested grain particles in faeces was reduced (P<0.01) with CA-treated barley grain. Glucose and urea concentrations were increased (P<0.01) in the blood of calves fed the CA-treated barley grain. Ruminal pH tended (P=0.08) to be decreased with more finely ground barley and was increased when barley grain was treated with CA. Total volatile fatty acid concentrations in the rumen did not differ among treatments (P>0.05). However, the molar proportion of propionate was increased (P=0.03) when barley was more finely ground, and that of acetate was increased (P=0.04) when CA was added to barley grain. The ruminal concentration of ammonia nitrogen was increased (P<0.01) and microbial nitrogen synthesis in the rumen tended to decrease by adding CA to barley. Treating barley grain with citric acid increased fibre digestibility of total mixed rations, attenuated the decrease in ruminal pH, and improved weight gain and feed efficiency in male Holstein growing calves fed a high-cereal diet (550 g cereal grain/kg diet).     

Ground,dry-rolled and steam-processed barley grain for midlactation Holstein cows

Fine grinding of barley grain has traditionally been considered to be a potential risk to rumen function, feed intake and milk yield. These concerns are thought to be reduced by steam-rolling or coarse dry rolling. We hypothesized that finely ground barley grain is as effective in stimulating feed intake and milk production as are dry- and steam-rolled barley grain, and so the objective was to determine effects of feeding either (1) finely ground, (2) steam-rolled, (3) finely dry-rolled, or (4) coarsely dry-rolled barley grain on rumen fermentation, digestibility and milk yield and composition. Eight multiparous midlactation Holstein cows were used in a replicated 4×4 Latin square design experiment with four periods of 21 d. Diets contained 256 g barley grain/kg on a dry matter (DM) basis. Processing method did not affect milk yield and composition, DM intake, rumen pH and volatile fatty acids, fecal and urine pH, and apparent total tract nutrient digestibility. Results suggest that finely ground barley grain is no different than dry-rolled and steam-rolled barley grains in stimulating feed intake and productivity of midlactation cows, when 256 g of dietary DM/kg is barley grain.     

Verification of marker–trait associations in biparental winter barley (<Emphasis Type="Italic">Hordeum vulgare</Emphasis> L.) DH populations

In previous genome-wide association studies, marker–trait associations for grain yield and additional traits of agronomic importance were identified in the German winter barley (Hordeum vulgare L.) breeding gene pool. In the present study, seven doubled haploid populations segregating for the relevant alleles at the associated loci were used to get information whether these marker–trait associations can be verified in biparental populations and reliably used in applied barley breeding. The doubled haploid populations were phenotyped in field trials at two to five locations each in 1 year and genotyped by 40 trait-associated single nucleotide polymorphisms using an Illumina VeraCode GoldenGate assay. Large phenotypic variation was observed for all traits within at least one doubled haploid population. For 19 out of 58 marker–trait associations tested, the phenotypic means of both marker classes were significantly (p ≤ 0.005) different, thus confirming the association of the respective marker and the quantitative trait locus detected. For example, doubled haploid lines derived from a cross of ‘Malta’ × ‘Goldmine’ carrying different marker alleles differed by 0.41 t/ha in mean grain yield. The 19 (out of 58) marker–trait associations verified correspond to 10 (out of 27) genomic regions. Markers that were verified to be associated with a quantitative trait locus can be implemented directly in winter barley breeding for the selection of parental lines and marker-assisted pedigree selection.     

Rumen digestion and microbial protein synthesis by growing lambs fed high-concentrate diets: Effects of cereal processing and animal age

Rumen digestion and microbial protein synthesis were studied using 36 growing lambs given either free choice access to separate feeders with whole barley grain and a pelleted soybean meal-based supplement (treatment WB) or a pelleted compound feed (treatment C) made by combining ground barley (0.65) with the same protein supplement (0.35). Free access to barley straw was offered in treatment C but not in WB. While both treatments were imposed before and after weaning (at 42 days), for a third treatment the compound feed was replaced after weaning by whole barley grain and the protein supplement without access to straw (treatment CWB). Six lambs from each treatment were slaughtered at 10 and 30 days post-weaning after ¹⁵N-labelling of microbial N and abomasal digesta flows were estimated using C₃₁ alkane as marker. Processing of barley grain increased (P<0.05) the apparent digestibility of dry matter in the rumen irrespective of age (0.53, 0.48 and 0.43 (S.E. 0.027) for C, CWB and WB). Ruminal pH averaged 5.5 (S.E. 0.06) regardless of cereal processing. The molar ratio of acetate to propionate decreased with age reflecting a higher proportion of grain in the mixed diets (WB and CWB) at 30 than 10 days post-weaning. Even with similar dietary proportions of grain and protein supplement, the acetate to propionate ratio was lower for lambs fed the free-choice (WB and CWB) vs. those fed the compound (C) diet (1.3 vs. 2.2 (S.E.D. 0.37)). Ruminal ammonia concentration increased with age and was lower for treatment C compared with treatments WB and CWB (24 vs. 127 (S.E.D. 22.2) mg/L), reflecting the higher protein intake of the latter two treatments. However, recovery of N intake as abomasal non-ammonia N was low for all treatments due to high protein intake and inefficient microbial growth compared to values reported for mixed diets. The efficiency of microbial N synthesis did not differ between treatments but it was negatively correlated (r = −0.73) with the organic matter apparently digested in the rumen, resulting in similar microbial yields in spite of the lower digestion in the rumen of whole barley diets. Feeding whole barley is thus a useful strategy to modify the site of digestion in intensive lamb fattening, allowing to reduce ruminal fermentation without depressing microbial N yield.     

Kernel texture and hordoindoline patterns in barley (Hordeum vulgare)

Hordoindolines, the tryptophan-rich polypeptides affecting grain hardness in barley, appeared as three pairs of polypeptides in the acidic polyacrylamide gel electrophoresis (A-PAGE) and two-dimensional A-PAGE?×?SDS-PAGE patterns of starch-granule proteins from 18 barley cultivars. On capillary RP-HPLC/nESI-MS/MS spectrometry, one pair of polypeptides was found to correspond to hordoindoline A (HINA), one to hordoindoline B1 (HINB1) and one to hordoindoline B2 (HINB2), the two polypeptides of each pair deriving from post-translational cleavage of a native hordoindoline at different positions at the N-terminus and/or C-terminus. Amongst the barley cultivars analyzed, cvs Hart and Sundance, which were claimed to be unique in lacking the Hina gene coding for HINA, revealed similar Hina coding sequences and accumulated hordoindoline HINA on their starch granules. The amount of total hordoindolines (HINA?+?HINB1?+?HINB2) on the starch granules, as quantified by densitometric scanning of A-PAGE gels, was comparable with that of puroindolines (PINA?+?PINB) in soft-textured wheat. By contrast, the amount of B-type hordoindolines (HINB1 and HINB2 combined) was 50?% lower than that of PINB, suggesting that the absence of barley cultivars with soft kernels is likely due to the reduced amount of B-type hordoindolines accumulated on the starch granules. Approximately 22 and 27?% of the phenotypic variation for kernel hardness in 56 barley cultivars analyzed by the Single Kernel Characterization System (SKCS) were explained by differences in kernel weight and B-type hordoindoline level, respectively. By contrast, the outer husk of barley grain showed no effect on the SKCS index.     

Estimation of the chlorophyll content and yield of grain crops via their chlorophyll potential

The results of the assessment of the relationship between the chlorophyll content, crop yield and chlorophyll potential of crops of wheat, barley, and oat are presented. The results of a ground-based remotesensing technique and laboratory data were used to accomplish this assessment. The spectral reflectance data of agricultural crops obtained using a ground-based remote-sensing technique in the Krasnoyarsk region were used to calculate the chlorophyll potential. Long-standing experiments have been carried out in different seasons, under various lighting conditions. Spectral measurements were performed using a double-beam spectroradiometer, which was installed on a mobile work platform at a height from 5 to 18 m. A good correlation between the chlorophyll content, grain yield, and chlorophyll potential of different cultivars of wheat, barley, and oat has been shown. It was also shown that the values of chlorophyll potential are different for wheat, barley, and oat cultivars in the growing season.     

Genetic and Morphometric Analysis of Cob Architecture and Biomass-Related Traits in the Intermated B73 × Mo17 Recombinant Inbred Lines of Maize

Expected future cellulosic ethanol production increases the demand for biomass in the US Corn Belt. With low nutritious value, low nitrogen content, and compact biomass, maize cobs can provide a significant amount of cellulosic materials. The value of maize cobs depends on cob architecture, chemical composition, and their relation to grain yield as primary trait. Eight traits including cob volume, fractional diameters, length, weight, tissue density, and grain yield have been analyzed in this quantitative trait locus (QTL) mapping experiment to evaluate their inheritance and inter-relations. One hundred eighty-four recombinant inbred lines of the intermated B73?×?Mo17 (IBM) Syn 4 population were evaluated from an experiment carried out at three locations and analyzed using genotypic information of 1,339 public SNP markers. QTL detection was performed using (1) comparison-wise thresholds with reselection of cofactors (α?=?0.001) and (2) empirical logarithm of odds score thresholds (P?=?0.05). Several QTL with small genetic effects (R ²?=?2.9–13.4 %) were found, suggesting a complex quantitative inheritance of all traits. Increased cob tissue density was found to add value to the residual without a commensurate negative impact on grain yield and therefore enables for simultaneous selection for cob biomass and grain yield.     

Identifying the critical period for waterlogging on yield and its components in wheat and barley

Background and aims

Crop tolerance to waterlogging depends on factors such as species sensitivity and the stage of development that waterlogging occurs. The aim of this study was to identify the critical period for waterlogging on grain yield and its components, when applied during different stages of crop development in wheat and barley.

Methods

Two experiments were carried out (E1: early sowing date, under greenhouse; E2: late sowing date, under natural conditions). Waterlogging was imposed during 15–20 days in 5 consecutive periods during the crop cycle (from Leaf 1 emergence to maturity).

Results

The greatest yield penalties occurred when waterlogging was applied from Leaf 7 appearance on the main stem to anthesis (from 34 to 92 % of losses in wheat, and from 40 to 79 % in barley for E1 and E2 respectively). Waterlogging during grain filling reduced yield to a lesser degree. In wheat, reductions in grain number were mostly explained by reduced grain number per spike while in barley, by variations in the number of spikes per plant.

Conclusions

The time around anthesis was identified as the most susceptible period to waterlogging in wheat and barley. Exposing the crop to more stressful conditions, e.g. delaying sowing date, magnified the negative responses to waterlogging, although the most sensitive stage (around anthesis) remained unchanged.