The effect of the opaque-2 gene on yield in maize

Summary It is difficult to use opaque-2 hybrids mainly because of their present low yield as compared with that of normal hybrids.Our studies were based on an experimental design allowing the comparison between 10 normal hybrids and their opaque-2 counterparts.The differences between normal and opaque-2 hybrids indicate that the opaque-2 (o ₂) gene chiefly affects kernel characters, and slightly some other characters.The observed phenotypical variability is mainly related with genetical causes. This means that the selection for suitable hybrid combinations may lessen the opaque-2 negative effects, which should be possible without modifying the protein quality of the opaque-2 maize.     

A recurrent selection programme for grain yield in winter barley

Summary The effect of a recurrent selection procedure was evaluated in a winter barley (Hordeum vulgare L.) population. Cycle zero (C₀) was initiated by crossing six high yielding winter barley cultivars with the short straw cv Onice. The F₁'s were crossed according to a diallel scheme without reciprocals. A total of 750 S₀ plants were derived and evaluated; 329 S₀ plants were selected and their progenies (S₁ lines) tested. Fifteen S₁ lines were chosen and used as parents of cycle 1 (C₁), by producing 105 F₁ hybrids which simulated a random mating offspring. One hundred and three randomly chosen S₁ lines belonging to C₀, and 103 S₁ lines belonging to C₁, were evaluated at two locations.For grain yield a significant difference between cycles was observed. From C₀ to C₁ the grain yield increased with 307 g/m². This increase was due to a higher number of seeds per m². For plant height, heading date and 100-kernel weight no differences between cycles were observed.The positive results obtained in this study indicate the potential usefulness of recurrent selection for developing parents or lines superior for grain yield, with little change in other important agronomic traits.     

Contribution of the Patagonia Icefields of South America to sea level rise

Digital elevation models of the Northern and Southern Patagonia Icefields of South America generated from the 2000 Shuttle Radar Topography Mission were compared with earlier cartography to estimate the volume change of the largest 63 glaciers. During the period 1968/1975-2000, these glaciers lost ice at a rate equivalent to a sea level rise of 0.042 +/- 0.002 millimeters per year. In the more recent years 1995-2000, average ice thinning rates have more than doubled to an equivalent sea level rise of 0.105 +/- 0.011 millimeters per year. The glaciers are thinning more quickly than can be explained by warmer air temperatures and decreased precipitation, and their contribution to sea level per unit area is larger than that of Alaska glaciers.     

Weak effects of habitat type on susceptibility to invasive freshwater species: an Italian case study

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Prognostic indicators for dogs with dilated cardiomyopathy

The purpose of this study was to investigate the prognostic value of various clinical, ECG, echocardiographic, and Doppler echocardiographic variables in dogs with dilated cardiomyopathy. The relationship to survival of 11 variables was evaluated in 63 dogs. Studied variables were age at time of diagnosis, class of heart failure (HF), dyspnea, ascites, atrial fibrillation (AF), ejection fraction (EF), E-point septal separation, end-diastolic volume index, end-systolic volume index (ESV-I), and restrictive or nonrestrictive transmitral flow (TMF) pattern. Median survival time was 671 days (lower 95% confidence limit, 350 days). Survival curves showed that severity of HF, ascites, ESV-I greater than 140 mL/m2, EF less than 25%, and restrictive TMF pattern had a significant negative relation to survival time. Thirty-nine dogs with both sinus rhythm and AF presented adequate TMF recordings; in these dogs, after stratification by TMF pattern, the restrictive TMF pattern was the most important negative prognostic indicator. We conclude that in dogs with dilated cardiomyopathy the restrictive TMF pattern appears to represent a useful prognostic indicator. Class of HF, ascites, ESV-I, and EF are also useful indexes if an adequate TMF pattern is not recorded.     

Competition between Ascorbate and Glutathione for the Oxidized Form of Methylated Quercetin Metabolites and Analogues: Tamarixetin, 4'O-Methylquercetin, Has the Lowest Thiol Reactivity

Quercetin (Q) is a bioactive compound with excellent antioxidant activity. However, the thiol reactivity of its oxidation product (oxQ) forms a disadvantage. The aim of the present study was to decrease this thiol toxicity. We found that methylated Q metabolites displayed lower thiol reactivity than Q. The most effective was tamarixetin, 4'O-methylquercetin (4'MQ), that has a corresponding oxidation product (ox4'MQ) with thiol reactivity 350 times lower than oxQ. The endogenous metabolism of Q to 4'MQ might be a physiological way to safely benefit from the antioxidant potential of Q in vivo. Our results were explained with Pearson's HSAB concept and corroborated by quantum molecular calculations that revealed a strong correlation between the relative thiol reactivity and the lowest unoccupied molecular orbital (LUMO). The polarity of the molecule and the π-π interaction between the AC- and the B-ring appeared to determine the LUMO and the thiol reactivity of the oxidation product.     

Performance of S2 Winter Barley Progenies from Original and Improved Populations Developed via Recurrent Selection

The effect of recurrent selection procedure for improving grain yield in autogamous cereals was evaluated in a six-rowed winter barley population. Gain from selection was estimated by field testing 90 random S2 lines from each of the C₀, C₁ and C₂ populations. Response to selection for grain yield was 0.78 t/ha from C₀ to C₁ and 1.09 t/ha from C₁ to C₂. Broad-sense heritability and genotypic variance for grain yield remained high in all cycles which suggests further gain from additional selection cycles. Yield increase was due to a higher number of seeds/m2. Significant differences among mean values were observed for heading date (189 days in C₀ and 182 days in C₂), whereas no variation was seen for plant height and 1000-kernel weight. The proposed recurrent selection procedure appears effective to improve the population and to extract superior genotypes for varietal development.     

Recurrent selection for seed quality traits in an opaque-2 maize population

Summary The aim of this research was to evaluate the response to phenotypic recurrent selection for four seed quality traits, i.e. protein content, dye binding capacity, tryptophan content, and specific weight, in a modified opaque-2 population of maize (Zea mays L.). Changes in other agronomic traits were also studied. Four selection cycles, using as selection criterion an index constructed from the four seed quality traits, were completed on an individual plant basis. The material from each cycle and from testerosses of each cycle with a homozygous opaque-2 tester was grown for two consecutive years to evaluate the progress due to selection. The results showed that four cycles of recurrent selection induced sizeable variations among cycles for all selected traits. The rate of progress for the four seed quality traits was nearly linear. Further-more, theldata show that improvement in seed-protein related traits had no negative effects on grain yield and kernel weight, when evaluated as the mean performance of testerosses. There was also no appreciable alteration in the other agronomic traits caused by selection for seed quality traits.     

Coincident scrapie infection and nephritis lead to urinary prion excretion

Prion infectivity is typically restricted to the central nervous and lymphatic systems of infected hosts, but chronic inflammation can expand the distribution of prions. We tested whether chronic inflammatory kidney disorders would trigger excretion of prion infectivity into urine. Urinary proteins from scrapie-infected mice with lymphocytic nephritis induced scrapie upon inoculation into noninfected indicator mice. Prionuria was found in presymptomatic scrapie-infected and in sick mice, whereas neither prionuria nor urinary PrP(Sc) was detectable in prion-infected wild-type or PrP(C)-overexpressing mice, or in nephritic mice inoculated with noninfectious brain. Thus, urine may provide a vector for horizontal prion transmission, and inflammation of excretory organs may influence prion spread.     

Comparison of primary mitral valve disease in German Shepherd dogs and in small breeds

The case records of 58 German Shepherds (GS group) affected by mitral valve prolapse (MVP) and/or mitral valve regurgitation (MR), and 49 dogs weighing < 15 kg (D group), affected by chronic valvular disease (CVD) were reviewed. The dogs of the GS group were presented more often without a detectable heart murmur (p < 0.01), and less frequently with a high intensity heart murmur (p < 0.01). Atrial fibrillation (AF) was more common in the GS group (p < 0.001). MVP associated with mitral valve thickening was more common in the D group (p < 0.001). Fractional shortening (FS) was lower (p < 0.0001) and end-systolic volume index (ESV-I) was increased (p < 0.0001) in the GS group, whereas end-diastolic volume index (EDV-I) did not differ between the 2 groups. Prevalence and severity of pulmonary hypertension were similar in the 2 groups. Dogs with mitral valve disease weighing more than 20 kg had a 5.8 higher chance of developing decreased FS, increased ESV-I, AF and ventricular arrhythmias. In the GS group, the decreased FS and increased ESV-I were not associated with the presence of AF or ventricular arrhythmias (p > 0.05). It appears that GS may be affected both by mitral valve prolapse and mitral insufficiency. It also appears that a comparatively large proportion of GS shows no major mitral valve thickening or MVP, but still presents with significant mitral regurgitation, possibly suggesting a different cause for the important incompetence observed in most cases.