Effect of genotypic, meteorological and agronomic factors on the gluten index of winter durum wheat

The determination of the gluten index is a widely used method for analysing the gluten strength of bread wheat and spring durum wheat genotypes. The present work was carried out to study the effect of the genotype, meteorological factors (temperature, precipitation and number of days with Tmax ≥ 30 °C) and agronomic treatments (N fertilisation and plant protection) on the gluten index of winter durum wheat varieties and breeding lines. The results indicated that the gluten index had little dependence on the environment, being determined to the greatest extent by the genotype. Compared with varieties having weak gluten, those with a strong gluten matrix responded less sensitively to changes in environmental conditions. Among the meteorological factors, high temperature at the end of the grain-filling period caused the greatest reduction in the mean gluten index of three varieties (R 2 = 0.462), while the fertiliser was found to be a significant factor affecting the gluten strength of winter durum wheat varieties. Using selection based on the gluten index, the gluten strength of winter durum wheat lines can be improved sufficiently to make them competitive with high quality spring varieties

Pathogen Populations Evolve to Greater Race Complexity in Agricultural Systems – Evidence from Analysis of Rhynchosporium secalis Virulence Data

Fitness cost associated with pathogens carrying unnecessary virulence alleles is the fundamental assumption for preventing the emergence of complex races in plant pathogen populations but this hypothesis has rarely been tested empirically on a temporal and spatial scale which is sufficient to distinguish evolutionary signals from experimental error. We analyzed virulence characteristics of ∼1000 isolates of the barley pathogen Rhynchosporium secalis collected from different parts of the United Kingdom between 1984 and 2005. We found a gradual increase in race complexity over time with a significant correlation between sampling date and race complexity of the pathogen (r20 = 0.71, p = 0.0002) and an average loss of 0.1 avirulence alleles (corresponding to an average gain of 0.1 virulence alleles) each year. We also found a positive and significant correlation between barley cultivar diversity and R. secalis virulence variation. The conditions assumed to favour complex races were not present in the United Kingdom and we hypothesize that the increase in race complexity is attributable to the combination of natural selection and genetic drift. Host resistance selects for corresponding virulence alleles to fixation or dominant frequency. Because of the weak fitness penalty of carrying the unnecessary virulence alleles, genetic drift associated with other evolutionary forces such as hitch-hiking maintains the frequency of the dominant virulence alleles even after the corresponding resistance factors cease to be used

Identification of wheat genotypes with adult plant resistance to powdery mildew

As in the case of other wheat diseases, adult plant resistance (APR) to powdery mildew remains effective longer than monogenic hypersensitive resistance, so the objective was to identify winter wheat genotypes with this type of resistance. Field and greenhouse tests conducted on 41 varieties and breeding lines indicated that 36 were susceptible in the seedling stage, and only five were resistant in all stages of development. It is probable that these latter genotypes contain major resistance genes. The area under the disease progress curve was the same for most of the wheat genotypes as for the APR control variety Massey, but varieties and lines with significantly better resistance were also identified. Among the genotypes in the Martonvásár breeding stock, Mv Táltos and the line Mv07-03 were found to have excellent adult plant resistance

Differentiation of barley yellow dwarf luteovirus serotypes infecting cereals and maize in Hungary

In 1994, a survey was carried out at 4 different locations in Hungary (Kiszombor, Kompolt, Martonvásár and Táplánszentkereszt) for the presence of barley yellow dwarf luteovirus (BYDV) serotypes in barley, wheat, triticale and maize. Leaf samples exhibiting symptoms of barley yellow dwarf virus were collected from cereal and maize plants. The number of samples collected was 119 from barley, 297 from wheat, 92 from triticale and 274 from maize. Diagnosis was done by double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA), using RPV, RMV, MAV, PAV and SGV diagnostics (Agdia). We determined that, among the barley yellow dwarf luteovirus serotypes, the PAV serotype was dominant in cereals at all locations. In maize both the RPV and RMV serotypes were present at high rates.Différenciation des sérotypes du virus de la jaunisse nanisante de l'orge (BYDV) qui infectent les céréales et le maïs en Hongrie. En 1994, une enquête a été réalisée dans 4 localités de Hongrie (Kiszombor, Kompolt, Martonvásár et Táplánszentkereszt) pour étudier la présence des sérotype du BYDV chez les orges, blé, triticale et maïs. Des échantillons de feuilles montrant des symptômes du BYDV ont été prélevés sur des plantes de céréales à paille et de maïs : 119 d'orge, 297 de blé, 92 de triticale et 274 de maïs. Le diagnostic viral par la méthode DAS-ELISA (double antibody sandwich enzyme-linked immunosorbent assay) a été utilisé pour les virus : RPV, RMV, MAV, PAV et SGV. Les résultats montrent que, parmi les sérotypes du BYDV, c'est le PA V qui est dominant dans les céréales des différentes localités. Chez le maïs, les sérotypes RPV et RMV sont présents à des taux élevés