Hemel Hempstead, United Kingdom
Hemel Hempstead, United Kingdom

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Huang Y.J.,University of Hertfordshire | Huang Y.J.,Rothamsted Research | Jestin C.,Terres Inovia | Jestin C.,French National Institute for Agricultural Research | And 9 more authors.
Theoretical and Applied Genetics | Year: 2016

Key message: Six stable QTL for resistance againstL. maculans(phoma stem canker) have been identified by QTL × environment interaction analysis using data from five winter oilseed rape field experiments. Abstract: Phoma stem canker, caused by Leptosphaeria maculans, is a disease of worldwide importance on oilseed rape (Brassica napus). Quantitative trait loci (QTL)-mediated resistance against L. maculans in B. napus is considered to be race non-specific and potentially durable. Identification and evaluation of QTL for resistance to L. maculans is important for breeding oilseed rape cultivars with durable resistance. An oilseed rape mapping population was used to detect QTL for resistance against L. maculans in five winter oilseed rape field experiments under different environments. A total of 17 QTL involved in ‘field’ quantitative resistance against L. maculans were detected and collectively explained 51 % of the phenotypic variation. The number of QTL detected in each experiment ranged from two to nine and individual QTL explained 2–25 % of the phenotypic variation. QTL × environment interaction analysis suggested that six of these QTL were less sensitive to environmental factors, so they were considered to be stable QTL. Markers linked to these stable QTL will be valuable for selection to breed for effective resistance against L. maculans in different environments, which will contribute to sustainable management of the disease. © 2015, The Author(s).

Gilks W.R.,Rothamsted Research | Gilks W.R.,University of Leeds | Welham S.J.,Rothamsted Research | Welham S.J.,VSN International Ltd | And 5 more authors.
Theoretical and Applied Genetics | Year: 2012

This paper develops a simple diagnostic for the investigation of uncertainty within genetic linkage maps using a Bayesian procedure. The method requires only the genotyping data and the proposed genetic map, and calculates the posterior probability for the possible orders of any set of three markers, accounting for the presence of genotyping error (mistyping) and for missing genotype data. The method uses a Bayesian approach to give insight into conflicts between the order in the proposed map and the genotype scores. The method can also be used to assess the accuracy of a genetic map at different genomic scales and to assess alternative potential marker orders. Simulation and two case studies were used to illustrate the method. In the first case study, the diagnostic revealed conflicts in map ordering for short inter-marker distances that were resolved at a distance of 8-12 cM, except for a set of markers at the end of the linkage group. In the second case study, the ordering did not resolve as distances increase, which could be attributed to regions of the map where many individuals were untyped. © 2012 Springer-Verlag.

Elek H.,KWS UK Ltd | Smart L.,Rothamsted Research | Martin J.,Rothamsted Research | Ahmad S.,Rothamsted Research | And 5 more authors.
Bulletin of Insectology | Year: 2013

As an environmentally compatible alternative to the use of conventional insecticides to control cereal aphids, the possibility of exploiting natural resistance to insect pests in wheat species was investigated. Previous work, comparing the antibiotic and antixenotic effects of hexaploid wheat (Triticum aestivum, AABBDD), tetraploid wheat (Triticum durum, AABB) and some A genome diploid species on the bird cherry-oat aphid, Rhopalosiphum padi L., found little difference between accessions in the higher ploidy plants, but the diploid species contained attributes that could be important in the breeding for resistance against aphids in the future. This study concentrated on wild accessions of diploid Aegilops species to which the closest ancestor of the B genome donor of hexaploid wheat belongs. The aphid R. padi showed reduced attraction and an increase in the intrinsic rate of population growth on the B genome species tested by compared to the hexaploid control. Investigation of a group of secondary metabolites, the hydroxamic acids or benzoxazinones showed that leaf tissue of one of these (Aegilops speltoides) contains high levels of DIMBOA-glucoside and of the main aglucone, 2,4-dihidroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA) while no hydroxamic acids were found in the leaf tissue of Ae. longissima, Ae. bicornis and Ae. sharonensis and only trace levels in Ae. searsii. In those species, an unknown compound was present, which may have an effect on aphid behaviour. The effect of aphid feeding on levels of hydroxamic acids in Ae. speltoides and Ae. sharonensis was also examined. While a localised defence reaction to aphid feeding had been identified in the hexaploid and tetraploid species, a more systemic effect was observed in the diploid Ae. speltoides.

Elek H.,KWS UK Ltd | Smart L.,Rothamsted Research | Martin J.,Rothamsted Research | Ahmad S.,Rothamsted Research | And 5 more authors.
Annals of Applied Biology | Year: 2013

The potential for exploiting natural wheat resistance to control the cereal aphid Rhopalosiphum padi, the most important aphid pest of small grain cereals in the UK, was investigated as an alternative approach to the use of insecticides. The investigation focussed on a group of secondary metabolites, the hydroxamic acids or benzoxazinones, present naturally as glucosides, but which hydrolyse on tissue damage to give biologically active aglycones, e.g. 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA) which are associated with natural plant defence. These can be important for resistance against insects, fungi, bacteria and nematodes for a range of cultivated monocotyledonous plants and could ultimately be combined with other defence mechanisms to provide a general approach to cereal aphid control. Levels of hydroxamic acids, particularly DIMBOA-glucoside, were determined in hexaploid (Triticum aestivum) and tetraploid (Triticum durum) wheat varieties and differences were found between species and varieties. The effect of feeding by R. padi on the level of hydroxamic acids in the leaf tissue was also investigated. Thus, after 24 h of aphid feeding, as an apparently localised hydrolytic defence reaction in the leaf, levels of DIMBOA-glucoside decreased noticeably. When aphids were fed on sucrose solution containing low doses of DIMBOA there was a significant mortality compared to the sucrose control. However, the levels of and variation in hydroxamic acids in the wheat varieties investigated were insufficient for significant differences in aphid behaviour and development. © 2012 KWS UK Limited. Annals of Applied Biology © 2012 Association of Applied Biologists.

PubMed | VSN International Ltd, proPlant GmbH, Rothamsted Research and Bayer AG
Type: Journal Article | Journal: Pest management science | Year: 2016

The reliance on and extensive use of pyrethroid insecticides have led to pyrethroid resistance in pollen beetle (Meligethes aeneus). Widespread adoption of best practice in pollen beetle management is therefore needed. Decision support systems (DSSs) that identify the risk period(s) for pest migration can help to target monitoring and control efforts, but they must be accurate and labour efficient to gain the support of growers. Weather data and the phenology of pollen beetles in 44 winter oilseed rape crops across England over 4 years were used to compare the performance of two risk management tools: the DSS proPlant expert, which predicts migration risk according to a phenological model and local weather data, and rule-based advice, which depends on crop growth stage and a temperature threshold.Both risk management tools were effective in prompting monitoring that would detect breaches of various control thresholds. However, the DSS more accurately predicted migration start and advised significantly fewer days of migration risk, consultation days and monitoring than did rule-based advice.The proPlant expert DSS reliably models pollen beetle phenology. Use of such a DSS can focus monitoring effort to when it is most needed, facilitate the practical use of thresholds and help to prevent unnecessary insecticide applications and the development of insecticide resistance.

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