Genetic improvement of the Pacific oyster Crassostrea gigas (Thunberg) in Australia

The Pacific oyster industry in Australia is derived from importations from Japan in the late 1940s and early 1950s to Tasmania and is almost completely hatchery based. This makes it a good target for developing and deploying genetically improved strains. An allozyme survey comparing hatchery stocks with self‐recruiting Tasmanian stocks and with two collections from Japan found abundant variation and no significant evidence of allele loss. The subsequent selection programme (initiated in the summer of 1996/97) had several strands. We wanted to take advantage of the increased power that marker‐assisted selection could bring and, therefore, needed to develop a linkage map and isolate flanking markers around quantitative trait loci (QTLs). Several types of markers (allozymes, microsatellites and AFLPs) were used, and single‐pair crosses were set up; QTLs have been detected. Conventional selection programmes, one based on mass selection and one on family selection, have been established. Triploid Pacific oysters produced via chemical means have been available for several years, but rates of triploidy achieved by such means are usually less than 100%. In 1999, we will assess whether our tetraploid 2‐year‐old broodstock can be crossed with diploids to give 100% triploid offspring.     

Effect of Steeping Conditions on Wet-Milling Characteristics of Hard Red Winter Wheat

A batch-wise small-scale wet-processing laboratory for whole wheat kernel has been designed and constructed to produce wheat starch and gluten from wheat grains. Hard red winter wheat kernels were steeped in three steeping media: SO₂ solution, lactic acid, and hydrochloric acid. Acid concentrations of 0.1, 0.3, and 0.5%, were used for SO₂ solutions and hydrochloric acid, and 0.1, 0.6, and 3.0% for lactic acid. After 16, 20, and 24 hr of steeping, the wheat was wet-milled. Yields and protein contents of wet-milling fractions were compared. Both high concentration of steeping media and long steeping time increased the starch yield and decreased the protein contents of the starch. However, the steeping time and acid concentration could be reduced from 24 to 20 hr and from 0.5 to 0.3%, respectively, without any statistically significant difference in starch yields or protein contents of the starch. Consistency and color of the starch were affected by both steeping time and acid concentrations of steeping media.     

Wound contamination and antimicrobial susceptibility of bacteria cultured during total ear canal ablation and lateral bulla osteotomy in dogs.

OBJECTIVE: To detect contamination of wound sites from surgical handling of excised tissues during total ear canal ablation and lateral bulla osteotomy in dogs, and to compare susceptibility of bacterial isolates to cefazolin with susceptibility to other antimicrobial agents. DESIGN: Prospective clinical study. ANIMALS: 13 dogs. PROCEDURE: Dogs were treated surgically for otitis externa and media via total ear canal ablation and lateral bulla osteotomy. Specimens for aerobic bacterial culture were obtained from SC tissue immediately following skin incision, tissues excised from the osseous bulla (after transection of the horizontal ear canal and lateral bulla osteotomy), and from SC tissue prior to skin closure. Antimicrobial susceptibility of bacterial isolates to various antibiotics was determined by use of a broth dilution assay. RESULTS: There was a significant association between isolation of Streptococcus canis and Escherichia coli from specimens from the osseous bulla and specimens from the SC tissues prior to skin closure, indicating contamination of the SC tissues during surgery. Seventy percent of bacterial isolates were susceptible to cefazolin. CLINICAL IMPLICATIONS: Measures to limit bacterial contamination resulting from tissue handling during total ear canal ablation and lateral bulla osteotomy are necessary. Bacteriologic culture of tissue of the osseous bulla and determination of antimicrobial susceptibility are recommended. Administration of cefazolin alone may not be efficacious for antimicrobial prophylaxis.     

Using 3D animations to teach intracellular signal transduction mechanisms: taking the arrows out of cells

Traditional methods of teaching intracellular biological processes and pathways use figures or flowcharts with the names of molecules linked with arrows. Many veterinary students, presented with such material, simply memorize the names or chemical structures of the molecules and are then likely to forget the material once the examination is completed. To address this problem, the authors designed, created, and field-tested new teaching media that incorporate realistic three-dimensional (3D) animations depicting the dynamic changes that occur in intracellular molecules during cellular activation. Testing found that veterinary students taught using traditional teaching media (e.g., lectures, handouts, textbooks) are proficient in memorizing the names and order of intracellular molecules but unable to appreciate the interactions between these elements or their spatial relationships within cells. In contrast, more than 90% of veterinary students taught using 3D animations not only recall the facts about the intracellular elements but also develop accurate mental images of the interactions among these molecules and their spatial relationships. These findings strongly suggest that the comprehension of complex biological processes by veterinary students can be enhanced by the use of dynamic 3D depictions of these processes in the classroom.     

Prediction of irrigation return flows through a hierarchical modeling approach

The quantity of water available for irrigation is getting scarce in many countries and it assumes great importance for assured crop production, especially in view of the erratic behavior of the monsoon. Thus, there is a pressing need to improve the water efficiency of irrigation systems. One-way of improving the efficiency of the irrigation system is reusing the return flow from the irrigation system. This task requires quantification of return flow, which still remains as a grey area in irrigation water management. The estimation of return flow from the irrigation system is usually obtained using thumb rules depending upon the site-specific conditions like command area conditions and soil properties. In this paper, a hierarchical modeling technique, namely, regression tree is developed for return flow estimation. Regression tree is built through binary recursive partitioning. The effective rainfall, inflow, consumptive water demand, and percolation loss are taken as predictor variables and return flow is treated as the target variable. The applicability of the hierarchical model is demonstrated through a case study of Periyar-Vaigai Irrigation System in Tamil Nadu, India. The model performance shows a good match between the simulated and the field measured return flow values. Results of statistical analysis indicated that the correlation coefficients are high for both single as well as double crop seasons.     

Inheritance of leaf angle in Triticum aestivum L.

Summary A 6×6 diallel was prepared to study the inheritance of leaf angle in T. aestivum L. Genetic analysis in terms of diallel cross parameters and graphic analysis indicated the control of additive gene effects in the expression of this character. The results of F₁ analysis were supported by the analysis of F₂ data.     

Hybrid grass-clump dwarfness in wheat: Physiology and genetics

Summary The growth of all grass-clump dwarfs is sensitive to temperature with low temperature giving rise to the grass-clump phenotype and high temperature producing normal phenotype. A continuous temperature of 26°C is required for normal growth of Type 1 dwarfs, a continuous temperature of 21°C is required for normal growth of Ty[e 2 dwarfs and a continuous temperature of 16°C is required for normal growth of Type 3 dwarfs.Genetic studies show that the inheritance of the grass-clump characteristic is due to three complementary dominant genes.The grass-clump growth habit is produced as a result of the temperature sensitivity of the apical meristem. In grass-clump plants low temperature treatment results in the cessation of cell division, DNA synthesis and phospholipid synthesis in the apical meristem. The primary temperature lesion has not been identified. Prolonged low temperature treatment of grass-clump plants results in extensive cell necrosis in a region just below the apical meristem; this cell death results in the permanent inactivation of the apical meristem.Supported in part by the National Research Council of Canada.