Culicoides antigen extract stimulates equine blood mononuclear (BMN) cell proliferation and the release of eosinophil adherence-inducing factor(s)

Intradermal injection of a Culicoides antigen extract (CAgX) induces T lymphocyte and eosinophil accumulation in the skin of horses with sweet itch. Blood mononuclear (BMN) cells from normal ponies proliferate when stimulated by mitogen (phytohaemagglutinin, PHA) or antigen (tetanus toxoid, TT) and, as shown here, release soluble factor(s) that induce eosinophil adherence. CAgX also caused concentration dependent proliferation of BMN cells from sweet itch and normal ponies [stimulation index: 29 (13) and 17 (7) for BMN cells from sweet itch and normal ponies, respectively during the active phase of disease; 4 microg protein ml(-1)CAgX; 168 h]. A heat labile factor(s) which caused eosinophil adherence was also released [sweet itch ponies: 6.0 (1.6) per cent adherence versus 1.3 (0.4) per cent; normal ponies: 6.6 (0.5) per cent adherence versus 0.9 (0.1) per cent for supernatants from CAgX (4 microg protein ml(-1); 48 hours) stimulated versus unstimulated BMN cells, respectively]. These results suggest that soluble proteins released from T lymphocytes could affect eosinophil function in the lesional skin of sweet itch horses.     

Comparison of genome segments 2, 7 and 10 of bluetongue viruses serotype 2 for differentiation between field isolates and the vaccine strain

Bluetongue (BT) virus serotype 2 (BTV 2) was first confirmed in Tunisia in February 2000 and has since spread northward and westward, infecting several other countries and islands, including Corsica, where clinical disease was reported in October 2000. BT was again reported on the Island in July 2001, some six months after a vaccination campaign against BTV 2. The molecular relationship between isolates of the BTV 2 Corsican wild-type viruses from 2000 and 2001, and the attenuated BTV 2 vaccine were determined by comparing corresponding sequences of genome segments 2, 7 and 10 with each other and with already published sequences available in the genome database. Complete genetic stability was observed between the isolates of the Corsican BTV 2. There was some divergence between the nucleotide sequences of segment 10 obtained from the wild-type and vaccine virus strains. Based on these differences, primers were selected that could be used in RT-PCR to differentiate between the wild-type and the vaccine viruses.     

First evidence of bluetongue virus in Kazakhstan

We report the results of the first serological survey for bluetongue virus in Kazakhstan. We analysed blood samples collected from 958 livestock and 513 wild saiga antelopes over a large area of the country, and found 23.2% seroprevalence in livestock and 0% in saigas. Seroprevalence in livestock did not vary by species, but increased significantly with age. There was no evidence for variation in seroprevalence at the regional level, but there was significant clustering at the farm level. Bluetongue has never before been reported in Kazakhstan, yet our results suggest that it may be endemic. We found seropositive animals at the furthest known northern limits of the bluetongue virus in this region of the world. Recorded vectors are not known to be present in Kazakhstan, so a novel vector is likely to be operating. The lack of evidence for bluetongue virus in saigas is unexpected and suggests a need for further investigation.     

The effect of environment on level of resistance to Phomopsis leptostromiformis in lupins and implications for resistance breeding to this disease

Summary Four varieties of lupins were sown at three planting dates and the level of Phomopsis leptostromiformis measured on the mature stems. When averaged over planting dates the varieties did not differ in resistance to this disease, however there were highly significant interactions between varieties and planting dates for level of disease. The implications of this result for resistance breeding to Phomopsis leptostromiformis are discussed.     

Genetic interpretations of the effects of bulk breeding on four populations of beans (Phaseolus vulgaris L.)

Summary The effects of bulk breeding on yield and its components in two high-yeilding and two low-yielding bean populations when grown at crop densities are interpreted in terms of gene action and selection. There was considerable additive variation in the crosses, dominance effects were variable but tended to be negative. The results were compared with results obtained at low density by another worker with the same populations, and this showed that interpretations of gene action in hybrid vigour depend on the test environment used. The interpretations were also compared with plant breeding interpretations made on the same material (Hamblin, 1977), and it was found that a single pattern of response to natural selection, in plant breeding terms, may be explained by more than one genetic interpretation and, conversely, a single genetic interpretation may result in different patterns of response in plant breeding terms. The value of composite crosses in plant breeding are discussed and it is concluded that there is a greater chance of producing improved lines from a large number of simple crosses than from a smaller number of composite crosses.     

Breeding implications of the relationship between competitive ability and pure culture yield in self-pollinated grain crops

Summary The relative efficiencies of pedigree and bulk breeding systems for selection of high yielding genotypes are shown to be dependent on the relationship between competitive ability in mixed culture and yield in pure culture. A critical statistic is the regression coefficient, , of competitive ability (defined as the yield of a genotype in mixed culture minus its yield in pure culture) on yield in pure culture. If is less than –1, competition in mixed culture so supresses genotypes which are high yielding in pure culture conditions that they are eliminated by natural selection in early generations; pedigree selection of the lowest yielding genotypes in the F₂ and F₃ is indicated. If is greater than –1, genotypes which are high yielding in pure culture survive even when they compete less well than low yielding genotypes, and bulk breeding is indicated. An example from two sets of 100 genotypes in pure and mixed culture was analysed and the estimate of fell between 0 and –1, but because exact simulation of a segregating population was not feasible the estimate was biased. The bias tended to give estimates of that were too close to zero.Agricultural Research Council Statistics Group, Department of Applied Biology, University of Cambridge England     

Relationship between barley grain yield measured in low- and high-yielding environments

Summary The paper addresses the general question of identifying the optimum environment for selection in plant breeding programs for low input agricultural systems. After defining low-yielding and high-yielding environments based on the average grain yield of large numbers of barley genotypes in different cropping seasons, we examined: 1) the phenotypic relationships between the highest yielding genotypes in low- and high-yielding environments, and 2) the genetic correlation coefficients between grain yield in low- and high-yielding environments. The results indicate that the alleles controlling high grain yield in low-yielding conditions are at least partially different from those controlling high grain yield in high-yielding conditions. Therefore, selection in high-yielding environments is expected to produce a negative response or no response in low-yielding environments. This may explain why crop varieties bred under high-yielding conditions failed to have an impact in low-yielding agricultural systems. The results may be extrapolated to systems where environmental concern suggests a reduction of inputs by raising the question of whether crop breeding programs based on selection under high inputs are likely to generate the right type of germplasm for an environmentally friendly agriculture.     

Inter-site transferability of crop varieties: another approach for analyzing multi-locational variety trials

Summary Improved crop varieties developed at experimental stations are intended for release for production in farmers' fields which are not necessarily the test sites. Therefore, it is important to measure the inter-site transferability of the crop variety. This study was undertaken to establish a statistical measure of inter-site transferability of a variety. Data on grain yield from two sets of multi-locational trials on barley and four sets of the wheat trials conducted by the Cereal Program, International Center for Agricultural Research in the Dry Areas, Syria, were analyzed to evaluate the inter-site transferability of the varieties. Genotype × environment interaction was significant and experimental errors were heterogeneous in each set of trials. Correlations between the slope (of linear regression of variety mean on location mean) and variety mean were significant (P < 0.01) in all trials. Correlations between the developed inter-site transferability statistic and the variety mean were significant (P < 0.05) in only two trials. Correlations between mean yield and probability of the inter-site transferability statistic were insignificant in all trials. The inter-site transferability statistic and the associated probability of the transferability may be used to select varieties which are high yielding as well as transferable to a new environment. The strong association of slope with mean yield restricted the scope of varietal selection but the introduced statistic did not suffer from this drawback.