Investigations on resistance of oats to Heterodera avenae: Location of resistance genes

Summary By using 15 available mono/nullisomic lines of Sun II back ground, the Heterodera avenae resistance gene in Nelson (from Avena sativa CI 3444) and Panema (from A. sterilis I. 376) were located on monosome XV. Genes with smaller effects were located on monosomes VIII and X. The absence of these genes derived from Sun II would increase cyst production on plants lacking major resistance genes.     

Marker-assisted selection for complex trait in common bean (Phaseolus vulgaris L.) using QTL-based index

A procedure was developed for marker-assisted selection of complex traits for common bean (Phaseolus vulgarisL.) using an index based on QTL-linked markers and ultrametric genetic distances between lines and a target parent. A comparison of the mean seed yields of the top five lines selected by different schemes demonstrated that the highest yielding group was selected on the basis of a combination of phenotypic performance and a high QTL-based index,followed by groups identified by a high QTL-based-index, conventional selection,and a low QTL-based-index. This study demonstrated a simple way to use information obtained from QTL studies to make selection decisions. The study also showed that the use of the QTL-based-index in conjunction with the ultrametric genetic distance to the target parent would enablea plant breeder to select lines that retain important QTL in a desirable genetic background. Therefore, this type of MAS would be expected to be superior to the phenotypic selection. This revised version was published online in August 2006 with corrections to the Cover Date.     

Comparison of Spring Barley Lines Produced by Single Seed Descent, Pedigree Inbreeding and Doubled Haploidy

Samples of inbred lines of Hordeum vulgare produced by pedigree inbreeding, doubled haploidy and single seed descent have been compared for a range of agronomic characters. Differences between the means of the in bred s produced by single seed descent and pedigree breeding were due to differing levels of inbreeding. The present study confirmed chat recombinant inbred families which out-perform the higher scoring parent may be produced by either method. Caution should, however, be exercised when simply inherited characters controlled by major genes are fixed in early generations. Differences between the doubled haploid and single seed descent samples for the character thousand grain weight were attributable to coupling linkages involving epistatic genes. The production and evaluation of random inbred lines should be considered as an alternative to pedigree methods of barley breeding.     

Designing grasses with a future – combining the attributes of Lolium and Festuca

Lolium species (considered the ideal grasses for European agriculture) are not sufficiently robust to meet many of the environmental challenges that face extensive agriculture in less favoured areas. Fortunately, adaptations to abiotic and biotic stresses exist amongst Festuca species related closely to Lolium. The complex of species has an enormous wealth of genetic variability and potentiality for genetic exchange, thus offering unique opportunities for the production of versatile hybrid varieties with new combinations of useful characters suited to modern grassland farming. The attributes of Lolium and Festuca can be combined into a single genotype by amphiploidy or alternatively, a limited number of characters can be selectively introgressed from Festucainto Lolium or vice versa. Androgenesis of the interspecific hybrids can generate genotypes combining characters that may not be recovered by sexual backcrossing. Genomic in situ hybridization(GISH) can differentially ‘paint’ the chromosomes of Lolium and Festuca and identify Lolium-Festuca recombinant chromosomes. GISH is valuable in the analysis of amphiploids, introgressions and androgenic genotypes and can be used to physically map introgressed traits. Introgression mapping is a powerful new approach to the mapping of traits and arises from a fusion of physical and genetic mapping. For example, in a diploidLolium introgression genotype with only one introgressed Festucasegment, the gene(s) for any Festucaderived trait expressed by the plant must be located within the segment. Using GISH and molecular markers, a dense but highly localised map of the Festuca segment is made in isolation of the Loliumgenome – this may simplify QTL analysis. This revised version was published online in July 2006 with corrections to the Cover Date.     

Responses of different arabica coffee (Coffea arabica L.) clones to varied environmental conditions

Different improved coffee arabica crosseshaving resistance to coffee berry diseaseand leaf rust, plus a standard cultivar,were grown under a range of environmentalconditions in a series of field trials inKenya. The effects of location and year ofproduction and their interactions with theclones were determined for berry yield.These data were used to estimate andcompare methods of analysis of GEI. An AMMImodel, joint regression model and ANOVAwith repeated measurements were used toinvestigate these interactions. The resultsindicated the relative effects of theclones and the environmental conditions,with Meru being the location where therewas greatest discrimination between theclones, probably because it was bettersuited for coffee. Clones,environments and joint regressions combinedaccounted for 31.20% of the interaction,leaving a residual of 68.80%. Significantresidual mean squares showed therelationship between clones andenvironments not to be strictly linear,thus indicating that regression analysisdid not always provide good estimates ofindividual clonal performance acrossenvironments. High correlations wereobtained between mean yield and regressioncoefficients and between ecovalence andmean square deviations as well as thecoefficient of determination. Resultsshowed that the improved clones surpassedthe standard cultivar both in terms ofyield and stability.Different analyses of the various aspectsof genotype response enabled the 21 clonesto be classified into different similaritygroups based on their performance andphenotypic stability as measured by variousstability parameters and the use of biplotsfrom the AMMI analysis.     

Genetic control over grain damage in a spring barley mapping population

A genetic map was constructed using DNA‐based markers in a barley mapping population derived from the cross ‘Tankard’בLivet’, that was developed to explore the genetic control over grain damage in spring barley cultivars. Quantitative trait loci (QTL) were located for husk skinning, gape between the lemma and palea and splitting of the fused pericarp/testa/aleurone tissues. The QTL accounted for 70% of the genetic variation in Split and 60% of the genetic variation in Gape and Skinning. The QTL were clustered on chromosomes 1H, 4H, 5H, 6H and 7H. QTL analysis indicates the possibility of transgressive segregation for grain splitting and so the breeding of lines with more extreme splitting. This is of concern to the malting industry as, without extensive phenotypic assessment, such lines could be commercialized, as was the case of Landlord, and put malting barley supplies at risk. These findings are discussed in relation to the genetic control over traits including grain length and width.     

Height,competition and yield potential in winter wheat

Summary A monogenic dominant male sterility is used for hybrid production in autumn and winter cauliflower. The ratio of male sterile plants in the backcross progenies of autumn cauliflower was 1:1 over five years (1987–1991). However, a significant deficit of male sterile plants was observed in the winter type over the same period.The influence of the temperature on the male sterile phenotype was studied within backcross progenies planted inside polythene tunnels. Six classes of phenotype were defined during the flowering period (from May to November). At low temperature, some male sterile plants developed partial to complete male fertility, whereas at high temperature, male fertile plants became male sterile.Segregation among the progenies of self-pollinated unstable male sterile plants did not deviate from the expected 3:1 ratio. Plants homozygous for the male sterility allele have been revealed by test crosses with a male fertile plant.For use in seed production, stable male sterile plants are vegetatively maintained; however, crossing lines isogenic except at the MS locus would allow male sterile plants to be raised from seed.     

Plant Location Patterns in the European Automobile Supplier Industry

Motor vehicle and motor vehicle parts production tend to exhibit a strong degree of agglomeration. We estimate a location model utilizing detailed plant‐level data for over 1,700 European locations of the largest motor vehicle parts suppliers, as well as the location of all light vehicle assembly plants operational in 2010. This unique data set allows us to estimate a location model for the region at a significantly higher level of resolution than the previous literature. The results suggest that the main forces of agglomeration in the European auto supplier sector are highway access and the desire to locate near assembly plants as well as near other parts‐producing plants.     

Development and application of functional markers in maize

Summary Functional markers (FMs) are derived from polymorphic sites within genes causally involved in phenotypic trait variation (Andersen, J.R. & T. Lübberstedt, 2003. Trends Plant Sci 8: 554–560). FM development requires allele sequences of functionally characterized genes from which polymorphic, functional motifs affecting plant phenotype can be identified. In maize and other species with low levels of linkage disequilibrium, association studies have the potential to identify sequence motifs, such as a few nucleotides or insertions/deletions, affecting trait expression. In one of the pioneering studies, nine sequence motifs in the dwarf8 gene of maize were shown to be associated with variation for flowering time (Thornsberry, J.M., M.M. Goodman, J. Doebley, S. Kresovich, D. Nielsen & E.S. Buckler, 2001. Nat Genet 28: 286–289). Proof of sequence motif function can be obtained by comparing isogenic genotypes differing in single sequence motifs. At current, the most appropriate approach for this purpose in crops is targeting induced local lesions in genomes (TILLING) (McCallum, C.M., L. Comai, E.A. Greene & S. Henikoff, 2000. Nat Biotechnol 18: 455–457). In central Europe, maize is mainly grown as forage crop, with forage quality as major trait, which can be determined as proportion of digestible neutral detergent fiber (DNDF). Brown midrib gene knock out mutations have been shown to be beneficial for forage quality but disadvantageous for overall agronomic performance. Two brown midrib genes (bm1 and bm3) have been shown to be involved in monolignol biosynthesis. These two and additional lignin biosynthesis genes have been isolated based on sequence homology. Additional candidate genes putatively affecting forage quality have been identified by expression profiling using, e.g., isogenic bm lines. Furthermore, we identified an association between a polymorphism at the COMT locus and DNDF in a collection of European elite inbred lines.     

Interfering with regular meiotic behaviour in Avena sativa as a method of incorporating the gene for mildew resistance from A. barbata

Summary The regular meiotic behaviour of the cultivated oat Avena sativa (2n=6x=42) is genetically controlled. The factors which control the diploid-like meiotic behaviour also restrict the amount of pairing that occurs between alien chromosomes and their homoeologues in A.sativa, and hence increases the difficulties of introducing desirable variation from wild species into the cultivated oat. A genotype of the diploid species A.longiglumis which interferes with the regular meiotic behaviour of A. sativa can be used to induce pairing between alien chromosomes and their corresponding chromosomes in A. sativa. Using this procedure the dominant gene conferring mildew resistance has been transferred from the tetraploid weed species A. barbata into the cultivated oat.