A Field Disease Evaluation Method for Selecting Wheats Resistant to Mycosphaerella graminicola

Reliable and efficient methods of selection are important for improving disease resistance. Three methods of field assessment of the Septoria tritici blotch disease, caused by Mycosphaerella graminicola (Fückel) Schroeter, were compared to identify the most reliable for selecting resistant wheats, Triticum aestivttm L. Nine cultivars which differed in disease reaction to plant height and maturity, and their progenies from several generations were used. The methods consisted of scoring chlorotic and necrotic leaf area covered with pycnidia on the flag leaf and the leaf below the flag leaf (flag leaf-1) as percent of the total leaf area, on a plant-basis, and the percent necrosis visually estimated on a plot-basis. Plot data were greatly influenced by environmental changes leading to inconsistent genetic results. The flag leaf and flag leaf-1 methods provided the most precise consistent results. The use of the flag leaf-1 method is suggested for selection.     

Dosage Response of Rye Genes in a Wheat Background

Wheat (Triticum aestivum L.) breeders often utilize alien sources to supply new genetic variation to their breeding programs. However, the alien gene complexes have not always behaved as desired when placed into a wheat background. The introgressed genes of interest may be linked to undesirable genes, expressed at low levels or not at all. The short arm of rye (Secale cereale L.) chromosome one (1RS) contains many valuable genes for wheat improvement. In order to study rye gene response to varying copy number, wheat lines were constructed which contained zero, two or four doses of 1RS. The meiotic behavior of rye chromosome 1R, and wheat/rye translocation chromosomes, 1AL/1RS and 1BL/1RS was studied in the F₁ hybrids between wheat lines carrying 1R or the translocation chromosomes. The IRS arm was transmitted at a very high frequency; 98 % of the F₂ plants had at least one of the chromosomes with a IRS arm. In addition, 44 % of the F₂ plants received at least one copy of the chromosomes from each parent. Analysis of the meiotic behavior of the IRS arm suggested that few euploid wheat gametes were formed. Therefore, most of the pollen must have contained IRS. It is unknown whether the lack of euploid wheat pollen could account for the high transmission frequency of the rye chromosomes. There may have been differential survival of the embryos receiving the rye chromosome as well.     

Scaling Aspen-FACE experimental results to century and landscape scales

The Aspen-FACE experiment generated 11 years of empirical data on the effect of CO₂ enrichment and elevated ozone on the growth of field-grown trees (maple, birch and six aspen clones) in northern Wisconsin, but it is not known how these short-term plot-level responses might play out at the landscape scale over multiple decades where competition, succession and disturbances interact with tree-level responses. In this study we used a forest landscape model (LANDIS-II) to scale these site level results to broader temporal and spatial scales. These general principles emerged from the results. (1) The productivity of taxa under future conditions is the primary determinant of short-term taxon dominance. (2) Longer-term, longevity and shade tolerance may supersede productivity as the determinant of importance, depending on the disturbance regime. This result offers hope that, even in the face of atmospheric changes, managers may have some control over future forest composition and carbon sequestration through modification of disturbance regimes. (3) Changes in the abundance of taxa were mostly gradual and none of the taxa were extirpated from the landscape, even under treatments for which they were poorly adapted. This suggests that as atmospheric conditions change, abrupt extirpations are expected to be rare. (4) Similarly, different taxa fared relatively well under different treatments. This suggests that maintaining species and genetic diversity is a prudent forest management strategy in the face of global change. (5) Accounting for spatial processes is important because seed dispersal and establishment may limit the ability of some species to colonize available habitat.     

Aluminum tolerance in triticale, wheat, and rye

Acid soils containing high levels of aluminum (Al) are known to severely limit plant growth on over 1.6 billion hectares worldwide. In the United States, a gradual decline in the pH of many soils both in the Great Plains as well as the Southeast, has caused many soils to become high in levels of free Al. This worldwide condition encouraged the analysis of wheat (Triticum aestivum L. em Thell.), triticale (X Triticosecale Wittmack), and rye (Secale cereale L.) germplasm from one of the major acid soil regions of the world (Brazil) in order to evaluate and compare the genetic potential of Al genes for cereal improvement. The objectives were to compare Al-tolerance levels in wheats, triticales, and ryes by measuring root elongation responses in Al-containing hydroponic nutrient solutions. Root elongation was impaired for all species grown in 1 mg/L concentrations of Al. Rye had the longest root regrowth and Al-sensitive wheats had the shortest root regrowth. The triticales containing a 2D(2R) substitution developed in the mid-1970s had the poorest root regrowth of all triticale types. The newly developed advanced triticale lines (AABBRR) yet to be released for commercial production showed the highest degree of Al tolerance of all the triticale types and approached or exceeded the levels observed in rye. This indicated that progress is being made in improving Al-tolerance of triticale in Brazil. Of all the old and new wheat varieties showing the highest degree of Al-tolerance, none of them were better than ‘BH 1146’ a variety that is at least 50 years old. This indicated that over the past 50 years, although Brazilian wheat breeders have made yield improvements in wheat production, they have not improved Al-tolerance. Rye showed a higher degree of Al-tolerance than the other cereals when tested in 1 mg/L of Al, but as expected, some variation was noted. This revised version was published online in August 2006 with corrections to the Cover Date.     

Interactions between viscerotropic velogenic Newcastle disease virus and pet birds of six species. II. Viral evolution through bird passage

Following in vivo studies in pet birds of 6 species, 279 Newcastle disease virus (NDV) reisolates were selected for characterization by the embryonated-chicken-egg mean-death-time, plaque-assay, hemagglutination-elution, and hemagglutinin-thermostability techniques. Initially, the 279 isolates were screened by the mean-death-time and plaque-assay techniques, and 5 sequential isolates were chosen for each of 3 budgerigars and 2 parrots for characterization by the other 2 in vitro assays to determine whether the Colorado Psittacine Isolate of viscerotropic velogenic (VV) NDV (COPI-VVNDV) had evolved during passage through pet birds. Nineteen isolates were then selected for chicken back-passage studies. Fifteen of the 19 isolates were chosen for potential avirulence for 8-week-old domestic chickens. The 4 remaining isolates produced large red plaques when assayed and were therefore used as virulent virus controls likely to be VVNDV. Subsequent in vitro characterization of selected back-passage chicken NDV isolates demonstrated little change in the 4 parameters originally evaluated for the pet-bird isolates used for the back-passage studies. Although the psittacine isolate slowly evolved to relatively avirulent strains of NDV by passage in pet birds, reversion did not occur during the chicken back-passage studies.     

Studies on the pharmacokinetics and pharmacodynamics of mirtazapine in healthy young cats

Mirtazapine pharmacokinetics was studied in 10 healthy cats. Blood was collected before, and at intervals up to 72 h after, oral dose of 3.75 mg (high dose: HD) or 1.88 mg (low dose: LD) of mirtazapine. Liquid chromatography coupled to tandem mass spectrometry was used to measure mirtazapine, 8-hydroxymirtazapine and glucuronide metabolite concentrations. Noncompartmental pharmacokinetic modeling was performed. Median half-life was 15.9 h (HD) and 9.2 h (LD). Using Mann-Whitney analysis, a statistically significant difference between the elimination half-life, clearance, area under the curve (AUC) per dose, and AUC(∞) /dose of the groups was found. Mirtazapine does not appear to display linear pharmacokinetics in cats. There was no significant difference in glucuronidated metabolite concentration between groups. Pharmacodynamics was studied in 14 healthy cats administered placebo, LD and HD mirtazapine orally once in a crossover, blinded trial. In comparison with placebo, cats ingested significantly more food when mirtazapine was administered. No difference in food ingestion was seen between HD and LD, but significantly more behavior changes were seen with the HD. Limited serum sampling during the pharmacodynamic study revealed drug exposure comparable with the pharmacokinetic study, but no correlation between exposure and food consumed. Mirtazapine (LD) was administered daily for 6 days with no drug accumulation detected.     

Analysis of the diagnostic accuracy of the gamma interferon assay for detection of bovine tuberculosis in U.S. herds

The goal of this study was to evaluate the test sensitivity (SE) and specificity (SP) of the gamma interferon (G-IFN) assay used for the detection of bovine tuberculosis (bTB) in U.S. cattle herds. In addition, the study assessed the association between G-IFN test results and bTB status of cattle, and explored different cut off values for classification of test results in adult cattle using receiver operating characteristics (ROC) curve analysis. Test SE was estimated using a population of 87 confirmed infected cattle from 14 herds distributed in 6 states. Test SP was estimated using a population of 4123 cattle representing 3000 premises in 3 states. These animals were from bTB free areas, accredited bTB free herds, or herds that were historically bTB free based on the absence of lesions found at slaughter and historical records of negative tests performed for bTB surveillance. The distribution of G-IFN results and its association with bTB infection status was also explored in a group of 914 exposed cattle in which infection was not confirmed. The results showed that the SE of the G-IFN for a cut-off value ≥0.1 was 83.9% (76.1, 91.6). The SP of the G-IFN was 90.7% (95% CI: 89.8, 91.6), 97% (95% CI: 96.5, 97.5), and 98.6%(95% CI: 98.2, 98.9), for cut off values of 0.1, 0.3, and 0.5, respectively. For a cut off value ≥0.1, the likelihood ratio of a positive G-IFN test was 9.03 (95% CI: 7.90, 10.31), and the likelihood ratio of a negative G-IFN test was 0.18 (95% CI: 0.11, 0.29). The area under the ROC curve was 0.976 (95% CI: 0.97, 0.98), characteristic of a highly accurate test. ROC analysis also showed that lower cut-off values, such as 0.1, have high SE with suitable SP for use in parallel testing, while cut-off values ranging between 0.3 and 0.6 provide the high SP desired in series-testing protocols with lower SE values. Findings from this study indicated that the G-IFN performs with high accuracy in the field, yielding SE and SP estimates comparable to those reported in previous evaluations (Ryan et al., 2000; Ameni et al., 2000; de la Rua-Domenech et al., 2006; Gormley et al., 2006).