Effects of collembolan grazing on fungal colonization of leaf litter

After a detailed field study of the leaf litter biota of an aspen poplar forest at the time of snow melt, and the confirmation of selective fungal feeding by field-collected specimens of Onychiurus subtenuis Folsom, an attempt was made to assess the effects of this selective feeding on the colonization of leaf litter by two common species of litter fungi. Simple microcosms held under controlled laboratory conditions were used in this study.The results showed that relatively low rates of selective grazing by the Collembola had potentially important effects on the competitive colonizing ability of the individual fungal species studied.     

Pre-determination of survival rate of apple and pear scions after X-ray treatment

Summary A simple method is described which makes it possible to pre-determine the survival rate of dormant scions of woody crops such as apple and pear after X-ray treatment.During early spring irradiated scions were kept on water in a warm glasshouse and the buds were left to sprout. It appeared that the relation between X-ray dose and percentage of buds surviving on the scions after 3–4 weeks was similar to the relation between dose and the percentage of irradiated grafts surviving after two growing seasons in the field. In sofar the dose at which 50% survival occurs is presumed to be the most efficient one, the method enables speedy determination of the most effective dose of X-ray treatment.     

Assessing single-nucleotide polymorphism selection methods for the development of a low-density panel optimized for imputation in South African Drakensberger beef cattle

A major obstacle in applying genomic selection (GS) to uniquely adapted local breeds in less-developed countries has been the cost of genotyping at high densities of single-nucleotide polymorphisms (SNP). Cost reduction can be achieved by imputing genotypes from lower to higher densities. Locally adapted breeds tend to be admixed and exhibit a high degree of genomic heterogeneity thus necessitating the optimization of SNP selection for downstream imputation. The aim of this study was to quantify the achievable imputation accuracy for a sample of 1,135 South African (SA) Drakensberger cattle using several custom-derived lower-density panels varying in both SNP density and how the SNP were selected. From a pool of 120,608 genotyped SNP, subsets of SNP were chosen (1) at random, (2) with even genomic dispersion, (3) by maximizing the mean minor allele frequency (MAF), (4) using a combined score of MAF and linkage disequilibrium (LD), (5) using a partitioning-around-medoids (PAM) algorithm, and finally (6) using a hierarchical LD-based clustering algorithm. Imputation accuracy to higher density improved as SNP density increased; animal-wise imputation accuracy defined as the within-animal correlation between the imputed and actual alleles ranged from 0.625 to 0.990 when 2,500 randomly selected SNP were chosen vs. a range of 0.918 to 0.999 when 50,000 randomly selected SNP were used. At a panel density of 10,000 SNP, the mean (standard deviation) animal-wise allele concordance rate was 0.976 (0.018) vs. 0.982 (0.014) when the worst (i.e., random) as opposed to the best (i.e., combination of MAF and LD) SNP selection strategy was employed. A difference of 0.071 units was observed between the mean correlation-based accuracy of imputed SNP categorized as low (0.01 < MAF ≤ 0.1) vs. high MAF (0.4 < MAF ≤ 0.5). Greater mean imputation accuracy was achieved for SNP located on autosomal extremes when these regions were populated with more SNP. The presented results suggested that genotype imputation can be a practical cost-saving strategy for indigenous breeds such as the SA Drakensberger. Based on the results, a genotyping panel consisting of ~10,000 SNP selected based on a combination of MAF and LD would suffice in achieving a <3% imputation error rate for a breed characterized by genomic admixture on the condition that these SNP are selected based on breed-specific selection criteria.     

Identification and mapping of quantitative resistance to late blight (<Emphasis Type="Italic">Phytophthora infestans</Emphasis>) in <Emphasis Type="Italic">Solanum habrochaites</Emphasis> LA1777

Late blight (Phytophthora infestans) can have devastating effects on tomato production over the whole world. Most of the commercial cultivars of tomato, Solanum lycopersicum, are susceptible. Qualitative and quantitative resistance has been described in wild relatives of tomato. In general qualitative resistance can more easily be overcome by newly evolved isolates. Screening of three S. habrochaites accessions (LA1033, LA2099 and LA1777) through a whole plant assay showed that accession LA1777 had a good level of resistance to several isolates of P. infestans. To explore the potential in this wild species, an introgression line (IL) population of S. habrochaites LA1777 was used to screen individual chromosome regions of the wild species by a detached leaf assay. Two major isolates (T_1,2 and T_1,2,4) were used and two parameters were measured: lesion size (LS), and disease incidence (DI). Substantial variation was observed between the individual lines. QTLs were identified for LS but not for DI. The presence of five QTLs derived from LA1777 (Rlbq4a, Rlbq4b, Rlbq7, Rlbq8 and Rlbq12) results in unambiguous higher levels of resistance. All QTLs co-localized with previously described QTLs from S. habrochaites LA2099 except QTL Rlbq4b, which is therefore a novel QTL.     

Induction of male flowering in gynoecious cucumbers (Cucumis sativus L.) by silver ions

Summary Silvernitrate (AgNO₃) and silverthiosulphate (Ag(S₂O₃)₂ ^3-) effectively induced male flowering in many nodes of 7 gynoecious cucumber genotypes in 3 glasshouse trials. A single spraying of the plants in the first true leaf stage with 3 mM Ag⁺ as Ag(S₂O₃)₂ ^3- or AgNO₃ (500 ppm) yielded many more staminate flowers than GA-3 (1500 ppm) and almost as many as 3 consecutive sprayings of GA-4/7 (50 ppm).Male flowering started about 3 weeks after treatment and lasted for a period of up to 4 weeks thereafter. Plants treated with silver ions did not elongate and grew normally; effective concentrations of AgNO₃ proved phytotoxic only in poor growing conditions, while Ag(S₂O₃)₂ ^3- never gave deleterious side-effects. Even very strongly female lines can be induced to male flowering with silver ions, thus increasing the feasibility of large scale seed production of gynoecious × gynoecious cucumber hybrids.     

Coronal access of the canine dentition.

Access preparation for endodontic treatment should be very exact, and knowledge of the anatomy of the teeth is a very important requirement for success. The use of radiographs is indispensable and should be used throughout endodontic treatment. The purpose of this paper is to discuss and illustrate correct coronal access for endodontic treatment in regard to the anatomy of the endodontic system. The most common teeth that require endodontic treatment are the canines, fourth maxillary premolars, first mandibular molars, incisors, and then the remaining premolars and molars. Special emphasis will be placed on coronal access of the canine, carnassial and incisor dentition.     

Changes in haematological and clinicochemical profiles in blood of apparently healthy slaughter pigs, collected at the farm and at slaughter, in relation to the severity of pathological-anatomical lesions.

Differences in haematological and clinicochemical profiles of blood of apparently healthy slaughter pigs collected at the farm and at slaughter were investigated in relation to the severity of pathological-anatomical lesions. For this purpose blood-samples of castrated male pigs were collected once at seven different farms and from the same pigs one to three days later at the slaughterhouse. In general, as far as the investigated blood variables are concerned, there were distinct and significant differences in the mean values between farm and slaughter blood-samples. As a rule the mean values of the investigated blood variables were higher in the slaughter blood than in the farm blood. The effects are most pronounced for leucocyte concentration and for the activity of the enzymes creatine kinase (CK), lactate dehydrogenase (LDH), aspartate aminotransferase (AST) and gamma-glutamyltransferase (gamma-GT). For the blood variables albumin, lymphocytes and magnesium there were significant, but not so strong interactions between the sites of blood-sampling and the groups, which were classified according to the severity of pathological-anatomical lesions. Despite the fact that there were significant differences in the mean values of blood profiles of the slaughter pigs between the sites of blood sampling, this effect was only manifest as a difference in the level of the values of the blood variables. This means that clinicochemical and haematological profiles from groups of pigs at slaughter reflect the herd's health status at the farm and can be used when monitoring it.(ABSTRACT TRUNCATED AT 250 WORDS)     

The influence of disease on feed and water consumption and on pharmacokinetics of orally administered oxytetracycline in pigs

In the present study the feed and water consumption and pharmacokinetic parameters of orally administered oxytetracycline were compared in clinically healthy pigs and in the same pigs following a challenge with Actinobacillus (Haemophilus) pleuropneumoniae toxins. Endobronchial challenge with A. pleuropneumniae toxins was accompanied by anorexia, increased lassitude, labored breathing, fever, and increased white blood cell counts. Pleuropneumonia was evident in all pigs on autopsy. Following the challenge, both feed and water consumption were markedly reduced. In contrast to recommendations in the literature, it is concluded that drugs should not be administered to pneumonic pigs via water. In healthy pigs the oral bioavailability of oxytetracycline (50 mg/kg), given on an empty stomach, was 4.8% and the elimination half-life (t1/2 beta) was 5.92 h. After challenge, the pigs showed great variation in oxytetracycline plasma concentrations. In addition, the mean computed elimination rate constant (beta), t1/2 beta, the area under the plasma concentration-time curve (AUC), and clearance in pneumonic pigs differed significantly (P less than .05) from the values found in healthy pigs. The elimination half-life (t1/2 beta), AUC, and volume of distribution (Vd area) were increased. In diseased pigs the mean of maximum plasma concentrations (.87 micrograms/ml) was reached after 7 h, in contrast to 1.74 h (1.87 micrograms/ml) in the healthy pigs.