Rising CO2 from historical concentrations enhances the physiological performance of Brassica napus seedlings under optimal water supply but not under reduced water availability.

The productivity of many important crops is significantly threatened by water shortage, and the elevated atmospheric CO2 can significantly interact with physiological processes and crop responses to drought. We examined the effects of three different CO2 concentrations (historical ~300 ppm, ambient ~400 ppm and elevated ~700 ppm) on physiological traits of oilseed rape (Brassica napus L.) seedlings subjected to well-watered and reduced water availability. Our data show (1) that, as expected, increasing CO2 level positively modulates leaf photosynthetic traits, leaf water-use efficiency and growth under non-stressed conditions, although a pronounced acclimation of photosynthesis to elevated CO2 occurred; (2) that the predicted elevated CO2 concentration does not reduce total evapotranspiration under drought when compared with present (400 ppm) and historical (300 ppm) concentrations because of a larger leaf area that does not buffer transpiration; and (3) that accordingly, the physiological traits analysed decreased similarly under stress for all CO2 concentrations. Our data support the hypothesis that increasing CO2 concentrations may not significantly counteract the negative effect of increasing drought intensity on Brassica napus performance.

Grass-Endophyte Interactions and Their Associated Alkaloids as a Potential Management Strategy for Plant Parasitic Nematodes.

Claviceptaceous endophytic fungi in the genus Epichloë mostly form a symbiotic relationship with cool-season grasses. Epichloë spp. are capable of producing bioactive alkaloids such as peramines, lolines, ergot alkaloids, and indole-diterpenes, which protect the host plant from herbivory by animals, insects, and nematodes. The host also benefits from enhanced tolerance to abiotic stresses, such as salt, drought, waterlogging, cold, heavy metals, and low nitrogen stress. The bioactive alkaloids produced can have both direct and indirect effects towards plant parasitic nematodes. Direct interaction with nematodes' motile stages can cause paralysis (nematostatic effect) or death (nematicidal effect). Indirectly, the metabolites may induce host immunity which inhibits feeding and subsequent nematode development. This review highlights the different mechanisms through which this interaction and the metabolites produced have been explored in the suppression of plant parasitic nematodes and also how the specific interactions between different grass genotypes and endophyte strains result in variable suppression of different nematode species. An understanding of the different grass-endophyte interactions and their successes and failures in suppressing various nematode species is essential to enable the proper selection of grass-endophyte combinations to identify the alkaloids produced, concentrations required, and determine which nematodes are sensitive to which specific alkaloids.

Effect of environment and variety on the relationships of wheat grain physical and chemical characteristics with ethanol yield.

BACKGROUND: Following the Renewable Transport Fuel Obligation (RTFO), there is an increasing demand for wheat grain for liquid biofuel in the UK. In order to enhance productivity of the bioethanol industry, good quality wheat must be used. RESULTS: A total of 84 grain samples comprising 14 varieties collected from 11 sites in two harvest years were analysed for a range of grain quality parameters and ethanol yield (EY). The grain quality parameters studied were starch and protein concentration, specific weight, grain density, packing efficiency, thousand-grain weight (TGW), grain length, width, length/width ratio and hardness index. Regression analysis was used to establish the relationships between grain quality parameters and EY. Apart from grain length and density, all grain parameters had significant relationships with EY. In the order of importance, protein concentration, TGW, packing efficiency and specific weight showed good relationships with EY. All other parameters, including starch concentration, showed a poor correlation with EY. EY and the relationship with the grain parameters were affected more by environment than by variety. Some sites gave consistently higher EY than others. When site and variety were considered with TGW and protein, a good prediction of EY could be made (variance accounted for = 87%). CONCLUSION: Combining TGW and protein concentration could be a better indicator of EY than the current practice of specific weight and protein.

Relationships between disease control, green leaf duration, grain quality and the production of alcohol from winter wheat.

BACKGROUND: Since demand for distilling wheat is expected to increase rapidly as a result of the development of the bioethanol industry, efficient production will become of increasing importance. Achieving this will require an understanding of the agronomic factors that influence both grain yield and alcohol yield. Therefore five field experiments using the winter distilling wheat variety Glasgow were conducted over three seasons (2006-2007, 2007-2008 and 2008-2009) to study the relationships between foliar disease and alcohol yield. RESULTS: There was a significant relationship between alcohol yield and the severity of the disease septoria leaf blotch (Septoria tritici), which was present in the experiments from natural infection. Retention of green flag leaf area as affected by disease control following fungicide application was also shown to be important for achieving high alcohol yields. Measurements of grain quality showed that high thousand-grain weight and low grain protein concentration were significantly related to increased alcohol yield. CONCLUSION: The experiments showed the importance of disease management to protect alcohol yields in the distilling wheat crop. Fungicides that provide greater disease control and improved green leaf retention are likely to be beneficial to alcohol yield.

Fungicide seed treatment efficacy against Microdochium nivale and M. majus in vitro and in vivo.

BACKGROUND: Seed-borne Microdochium majus (Wollenweber) and M. nivale Fries are the primary pathogens responsible for Fusarium seedling blight in the UK. The two species show differences in pathogenicity, host preference and sensitivities to temperature, but their relative sensitivities to fungicide seed treatments are unknown. The aim was firstly to determine the efficacy of fungicide seed treatments towards single-spore isolates of M. majus and M. nivale using in vitro experiments, and subsequently to determine efficacy in vivo over a range of temperatures. RESULTS: Differences in EC(50) values between all seed treatments were evident from the in vitro experiments and ranged from 0.028 mg L(-1) for fludioxonil to 22.8 mg L(-1) for carboxin + thiram. The two seed treatments that showed best performance in vitro were used to examine efficacy towards seed-borne infection in vivo at 4, 8, 12 and 16 degrees C. Generally, seedling emergence improved and the severity of stem-base disease symptoms on emerged seedlings was reduced for both species through the use of the fungicides. The combination of fludioxonil + difenconazole showed improved performance compared with fludioxonil alone. Significantly less severe symptoms were observed through the use of fludioxonil and fludioxonil + difenconazole compared with bitertanol + fuberidazole at 12 degrees C and for all except one M. nivale infected seed lot at 8 degrees C. CONCLUSIONS: Differences in fungicide sensitivity between the two species in vitro were not evident in vivo. This is the first report of the effect of fungicide seed treatments on the control of seedling blight caused by M. majus and M. nivale.

Molecular studies to identify the Fusarium species responsible for HT-2 and T-2 mycotoxins in UK oats.

High levels of Fusarium mycotoxins HT-2 and T-2 have been detected in UK oats since surveys started in 2002. Fusarium langsethiae and the closely related species F. sporotrichioides have previously been associated with the contamination of cereals with type A trichothecenes HT-2 and T-2 in Nordic countries. Preliminary microbiological analysis of UK oat samples with high concentrations of HT-2 and T-2 detected and isolated F. langsethiae and F. poae but not the other type A trichothecene producing species F. sporotrichioides, F. sibiricum and F. armeniacum. Two hundred and forty oat flour samples with a known mycotoxin profile were selected from a previous four year study (2002-2005) to cover the full concentration range from below the limit of quantification (<20 µg/kg) to 9,990 µg/kg HT-2+T-2 combined. All samples were analysed for the DNA of F. langsethiae, F. poae and F. sporotrichioides based on previously published PCR assays. F. langsethiae was detectable in nearly all samples; F. poae was detected in 90% of samples whereas F. sporotrichioides was not detected in any sample. A real-time PCR assay was developed to quantify F. langsethiae DNA in plant material. The assay could quantify as low as 10(-4)ngF. langsethiae DNA/µl. Based on this assay and a previously published assay for F. poae, both species were quantified in the oat flour samples with known HT-2+T-2 content. Results showed a good regression (P<0.001, r(2)=0.60) between F. langsethiae DNA and HT-2+T-2 concentration. F. poae DNA concentration was not correlated to HT2+T2 concentration (P=0.448) but was weakly correlated to nivalenol concentration (P<0.001, r(2)=0.09). Multiple regression with F. langsethiae and F. poae DNA as explanatory variates identified that both F. langsethiae and F. poae DNA were highly significant (P<0.001) but F. poae DNA only accounted for an additional 4% of the variance and the estimate was negative, indicating that higher concentrations of F. poae DNA were correlated with slightly lower concentrations of HT2+T2 detected. A stronger regression (P<0.001, r(2)=0.77) between F. langsethiae DNA and HT-2+T-2 was obtained after extraction and quantification of DNA and mycotoxins from individual oat grains. The results from this study provide strong evidence that F. langsethiae is the primary, if not sole, fungus responsible for high HT-2 and T-2 in UK oats.

Phylogenetic analysis of EF-1 alpha gene sequences from isolates of Microdochium nivale leads to elevation of varieties majus and nivale to species status.

Degenerate PCR primers were designed based on EF-1 alpha (EF-1alpha) gene sequences of several filamentous fungi retrieved from sequence databases. These primers were used to isolate a partial sequence, approximately 830 bp in length of the EF-1alpha from isolates of Microdochium nivale obtained from various geographic locations across the world. Two distinct groups of isolates were evident among those isolates examined. Sequence homology for comparisons within group was 99.7% for group A and 99.8% for group B. Primers specific to either group A or group B sequences were designed and tested on isolates from around the world. Comparisons were made with primers previously reported for the two varieties of M. nivale and revealed that Group A type isolates correlated with M. nivale var. majus and group B isolates with M. nivale var. nivale. The primers from this study and those previously reported were in agreement for all isolates with the exception of one isolate (NRRL 3289) which failed to amplify with previously published M. nivale primers. Sequence analysis of NRRL 3289 suggested that it was an isolate of M. nivale var. nivale as indicated by the EF-1alpha based primers developed in this study. This study provides sequence based phylogenetic evidence of two species and when taken together with biological differences reported, leads to the recognition of M. majus comb. nov. (syn. Fusarium nivale var. majus). Descriptions of the two species are provided.