The Locus on Wheat Chromosome 2B Controls Major Natural Variation for Floret Sterility Responses to Heat Stress at Booting Stage.

Heat stress at booting stage causes significant losses to floret fertility (grain set) and hence yield in wheat ( L.); however, there is a lack of well-characterized sources of tolerance to this type of stress. Here, we describe the genetic analysis of booting stage heat tolerance in a cross between the Australian cultivars Drysdale (intolerant) and Waagan (tolerant), leading to the definition of a major-effect tolerance locus on the short arm of chromosome 2B, ().

Fine mapping of root lesion nematode (Pratylenchus thornei) resistance loci on chromosomes 6D and 2B of wheat.

Resistance QTL to root lesion nematode (Pratylenchus thornei) in wheat (Triticum aestivum), QRlnt.sk-6D and QRlnt.sk-2B, were mapped to intervals of 3.

Diverging temperature responses of CO2 assimilation and plant development explain the overall effect of temperature on biomass accumulation in wheat leaves and grains.

There is a growing consensus in the literature that rising temperatures influence the rate of biomass accumulation by shortening the development of plant organs and the whole plant and by altering rates of respiration and photosynthesis. A model describing the net effects of these processes on biomass would be useful, but would need to reconcile reported differences in the effects of night and day temperature on plant productivity. In this study, the working hypothesis was that the temperature responses of CO assimilation and plant development rates were divergent, and that their net effects could explain observed differences in biomass accumulation.

Modelling and genetic dissection of staygreen under heat stress.

Staygreen traits are associated with heat tolerance in bread wheat. QTL for staygreen and related traits were identified across the genome co-located with agronomic and physiological traits associated to plant performance under heat stress. Plant chlorophyll retention-staygreen-is considered a valuable trait under heat stress.

Truncation of grain filling in wheat (Triticum aestivum) triggered by brief heat stress during early grain filling: association with senescence responses and reductions in stem reserves.

Short heat waves during grain filling can reduce grain size and consequently yield in wheat (Triticum aestivum L.). Grain weight responses to heat represent the net outcome of reduced photosynthesis, increased mobilisation of stem reserves (water-soluble carbohydrates, WSC) and accelerated senescence in the grain.

A QTL on the short arm of wheat (Triticum aestivum L.) chromosome 3B affects the stability of grain weight in plants exposed to a brief heat shock early in grain filling.

Background: Molecular markers and knowledge of traits associated with heat tolerance are likely to provide breeders with a more efficient means of selecting wheat varieties able to maintain grain size after heat waves during early grain filling.

Results: A population of 144 doubled haploids derived from a cross between the Australian wheat varieties Drysdale and Waagan was mapped using the wheat Illumina iSelect 9,000 feature single nucleotide polymorphism marker array and used to detect quantitative trait loci for heat tolerance of final single grain weight and related traits. Plants were subjected to a 3 d heat treatment (37 °C/27 °C day/night) in a growth chamber at 10 d after anthesis and trait responses calculated by comparison to untreated control plants.

Post-anthesis heat and a Gpc-B1 introgression have similar but non-additive effects in bread wheat.

High temperatures during grain filling can reduce the yield of wheat and affect its grain protein concentration. The Gpc-B1 locus of wheat also affects grain protein concentration, but it is not known whether its effects interact with those of heat. The aim of this study was to investigate the effects of high temperature in lines with and without functional (high-protein) alleles at Gpc-B1.

Variation in the interaction between alleles of HvAPETALA2 and microRNA172 determines the density of grains on the barley inflorescence.

Within the cereal grasses, variation in inflorescence architecture results in a conspicuous morphological diversity that in crop species influences the yield of cereal grains. Although significant progress has been made in identifying some of the genes underlying this variation in maize and rice, in the temperate cereals, a group that includes wheat, barley, and rye, only the dosage-dependent and highly pleiotropic Q locus in hexaploid wheat has been molecularly characterized. Here we show that the characteristic variation in the density of grains along the inflorescence, or spike, of modern cultivated barley (Hordeum vulgare) is largely the consequence of a perturbed interaction between microRNA172 and its corresponding binding site in the mRNA of an APELATA2 (AP2)-like transcription factor, HvAP2.

Fine mapping and chromosome walking towards the Ror1 locus in barley (Hordeum vulgare L.).

The Ror1 gene was fine-mapped to the pericentric region of barley chromosome 1HL. Recessively inherited loss-of-function alleles of the barley (Hordeum vulgare) Mildew resistance locus o (Mlo) gene confer durable broad-spectrum disease resistance against the obligate biotrophic fungal powdery mildew pathogen Blumeria graminis f.sp.

HVP10 encoding V-PPase is a prime candidate for the barley HvNax3 sodium exclusion gene: evidence from fine mapping and expression analysis.

In cereals, a common salinity tolerance mechanism is to limit accumulation of Na(+) in the shoot. In a cross between the barley variety Barque-73 (Hordeum vulgare ssp. vulgare) and the accession CPI-71284 of wild barley (H.

The CC-NB-LRR-type Rdg2a resistance gene confers immunity to the seed-borne barley leaf stripe pathogen in the absence of hypersensitive cell death.

Background: Leaf stripe disease on barley (Hordeum vulgare) is caused by the seed-transmitted hemi-biotrophic fungus Pyrenophora graminea. Race-specific resistance to leaf stripe is controlled by two known Rdg (Resistance to Drechslera graminea) genes: the H. spontaneum-derived Rdg1a and Rdg2a, identified in H.

HvNax3--a locus controlling shoot sodium exclusion derived from wild barley (Hordeum vulgare ssp. spontaneum).

Previous work identified the wild barley (Hordeum vulgare ssp. spontaneum) accession CPI-71284-48 as being capable of limiting sodium (Na(+)) accumulation in the shoots under saline hydroponic growth conditions. Quantitative trait locus (QTL) analysis using a cross between CPI-71284-48 and a selection of the cultivated barley (H.

Varietal and chromosome 2H locus-specific frost tolerance in reproductive tissues of barley (Hordeum vulgare L.) detected using a frost simulation chamber.

Exposure of flowering cereal crops to frost can cause sterility and grain damage, resulting in significant losses. However, efforts to breed for improved low temperature tolerance in reproductive tissues (LTR tolerance) has been hampered by the variable nature of natural frost events and the confounding effects of heading time on frost-induced damage in these tissues. Here, we establish conditions for detection of LTR tolerance in barley under reproducible simulated frost conditions in a custom-built frost chamber.

Flt-2L, a locus in barley controlling flowering time, spike density, and plant height.

Flowering time represents an important adaptive trait for temperate cereal crops and may also impact on frost damage in cereal reproductive tissues by enabling escape or by influencing accumulation of genuine tolerance. The Flowering time-2L (Flt-2L) quantitative trait locus (QTL) on the distal end of barley chromosome arm 2HL overlaps with QTL for rachis internode length and reproductive frost damage. Flt-2L was also found to be associated with plant height.

Genes and traits associated with chromosome 2H and 5H regions controlling sensitivity of reproductive tissues to frost in barley.

Frost at flowering can cause significant damage to cereal crops. QTL for low temperature tolerance in reproductive tissues (LTR tolerance) were previously described on barley 2HL and 5HL chromosome arms. With the aim of identifying potential LTR tolerance mechanisms, barley Amagi Nijo x WI2585 and Haruna Nijo x Galleon populations were examined for flowering time and spike morphology traits associated with the LTR tolerance loci.

Structure-function analysis of the barley genome: the gene-rich region of chromosome 2HL.

A major gene-rich region on the end of the long arm of Triticeae group 2 chromosomes exhibits high recombination frequencies, making it an attractive region for positional cloning. Traits known to be controlled by this region include chasmogamy/cleistogamy, frost tolerance at flowering, grain yield, head architecture, and resistance to Fusarium head blight and rusts. To assist these cloning efforts, we constructed detailed genetic maps of barley chromosome 2H, including 61 polymerase chain reaction markers.

Histological and molecular analysis of Rdg2a barley resistance to leaf stripe.

Barley (Hordeum vulgare L.) leaf stripe is caused by the seed-borne fungus Pyrenophora graminea. We investigated microscopically and molecularly the reaction of barley embryos to leaf stripe inoculation.

Lazy males? Bioenergetic differences in energy acquisition and metabolism help to explain sexual size dimorphism in percids.

1. Differences in energy use between genders is a probable mechanism underlying sexual size dimorphism (SSD), but testing this hypothesis in the field has proven difficult. We evaluated this mechanism as an explanation for SSD in two North American percid species--walleye Sander vitreus and yellow perch Perca flavescens.

Boron-toxicity tolerance in barley arising from efflux transporter amplification.

Both limiting and toxic soil concentrations of the essential micronutrient boron represent major limitations to crop production worldwide. We identified Bot1, a BOR1 ortholog, as the gene responsible for the superior boron-toxicity tolerance of the Algerian barley landrace Sahara 3771 (Sahara). Bot1 was located at the tolerance locus by high-resolution mapping.

Fine mapping and targeted SNP survey using rice-wheat gene colinearity in the region of the Bo1 boron toxicity tolerance locus of bread wheat.

Toxicity due to high levels of soil boron (B) represents a significant limitation to cereal production in some regions, and the Bo1 gene provides a major source of B toxicity tolerance in bread wheat (Triticum aestivum L.). A novel approach was used to develop primers to amplify and sequence gene fragments specifically from the Bo1 region of the hexaploid wheat genome.

RAR1, ROR1, and the actin cytoskeleton contribute to basal resistance to Magnaporthe grisea in barley.

The fungus Magnaporthe grisea, the causal agent of rice blast disease, is a major pathogen of rice and is capable of producing epidemics on other cultivated cereals, including barley (Hordeum vulgare). We explored the requirements for basal resistance of barley against a compatible M. grisea isolate using both genetic and chemical approaches.

SNARE-protein-mediated disease resistance at the plant cell wall.

Failure of pathogenic fungi to breach the plant cell wall constitutes a major component of immunity of non-host plant species--species outside the pathogen host range--and accounts for a proportion of aborted infection attempts on 'susceptible' host plants (basal resistance). Neither form of penetration resistance is understood at the molecular level. We developed a screen for penetration (pen) mutants of Arabidopsis, which are disabled in non-host penetration resistance against barley powdery mildew, Blumeria graminis f.

Resistance and susceptibility of plants to fungal pathogens.

Plants are under continuous threat of infection by pathogens endowed with diverse strategies to colonize their host. Comprehensive biochemical and genetic approaches are now starting to reveal the complex signaling pathways that mediate plant disease resistance. Initiation of defense signaling often involves specific recognition of invading pathogens by the products of specialized host resistance (R) genes.

Genetic and molecular characterization of the maize rp3 rust resistance locus.

In maize, the Rp3 gene confers resistance to common rust caused by Puccinia sorghi. Flanking marker analysis of rust-susceptible rp3 variants suggested that most of them arose via unequal crossing over, indicating that rp3 is a complex locus like rp1. The PIC13 probe identifies a nucleotide binding site-leucine-rich repeat (NBS-LRR) gene family that maps to the complex.