Genetic contributions to agricultural sustainability

The current tools of enquiry into the structure and operation of the plant genome have provided us with an understanding of plant development and function far beyond the state of knowledge that we had previously. We know about key genetic controls repressing or stimulating the cascades of gene expression that move a plant through stages in its life cycle, facilitating the morphogenesis of vegetative and reproductive tissues and organs. The new technologies are enabling the identification of key gene activity responses to the range of biotic and abiotic challenges experienced by plants. In the past, plant breeders produced new varieties with changes in the phases of development, modifications of plant architecture and improved levels of tolerance and resistance to environmental and biotic challenges by identifying the required phenotypes in a few plants among the large numbers of plants in a breeding population. Now our increased knowledge and powerful gene sequence-based diagnostics provide plant breeders with more precise selection objectives and assays to operate in rationally planned crop improvement programmes. We can expect yield potential to increase and harvested product quality portfolios to better fit an increasing diversity of market requirements. The new genetics will connect agriculture to sectors beyond the food, feed and fibre industries; agri-business will contribute to public health and will provide high-value products to the pharmaceutical industry as well as to industries previously based on petroleum feedstocks and chemical modification processes.     

克隆动物研究进展

本文介绍了世界上和中国采用细胞核移植技术克隆动物的研究历史。综述了细胞核移植的程序、方法和影响因素,包括受体卵母细胞的去核、供体细胞核的制备、核移植、激活、受体细胞与供体细胞的融合、重组胚的体内和体外培养以及胚胎移植产生克隆动物。对克隆动物研究和应用前景进行了讨论。近期的研究结果表明,多代克隆可产生大量遗传性相同的动物,不久的将来克隆技术在商业上的应用将成为现实。     

FURTHER OBSERVATIONS ON THE BREEDING BEHAVIOUR OF LABEO UMBRATUS (SMITH) (PISCES: CYPRINIDAE)

SUMMARY

Breeding behaviour of Labeo umbratus was observed in the Modder River, Orange Free State, and ova were collected from below the site and hatched. Fry were reared for 12 months to confirm the identification of the ova collected. The behaviour of spawning fish and the oviposition site are described.     

Quantitative genetics,version 3.0: where have we gone since 1987 and where are we headed?

The last 20 years since the previous World Congress have seen tremendous advancements in quantitative genetics, in large part due to the advancements in genomics, computation, and statistics. One central theme of this last 20 years has been the exploitation of the vast harvest of molecular markers—examples include QTL and association mapping, marker-assisted selection and introgression, scans for loci under selection, and methods to infer degree of coancestry, population membership, and past demographic history. One consequence of this harvest is that phenotyping, rather than genotyping, is now the bottleneck in molecular quantitative genetics studies. Equally important have been advances in statistics, many developed to effectively use this treasure trove of markers. Computational improvements in statistics, and in particular Markov Chain Monte Carlo (MCMC) methods, have facilitated many of these methods, as have significantly improved computational abilities for mixed models. Indeed, one could argue that mixed models have had at least as great an impact in quantitative genetics as have molecular markers. A final important theme over the past 20 years has been the fusion of population and quantitative genetics, in particular the importance of coalescence theory with its applications for association mapping, scans for loci under selection, and estimation of the demography history of a population. What are the future directions of the field? While obviously important surprises await us, the general trend seems to be moving into higher and higher dimensional traits and, in general, dimensional considerations. We have methods to deal with infinite-dimensional traits indexed by a single variable (such as a trait varying over time), but the future will require us to treat much more complex objects, such as infinite-dimensional traits indexed over several variables and with graphs and dynamical networks. A second important direction is the interfacing of quantitative genetics with physiological and developmental models as a step towards both the gene–phenotype map as well as predicting the effects of environmental changes. The high-dimensional objects we will need to consider almost certainly have most of their variation residing on a lower (likely much lower) dimensional subspace, and how to treat these constraints will be an important area of future research. Conversely, the univariate traits we currently deal with are themselves projections of more complex structures onto a lower dimensional space, and simply treating these as univariate traits can result in serious errors in understanding their selection and biology. As a field, our future is quite bright. We have new tools and techniques, and (most importantly) new talent with an exciting international group of vibrant young investigators who have received their degrees since the last Congress. One cloud for concern, however, has been the replacement at many universities of plant and animal breeders with plant and animal molecular biologists. Molecular tools are now an integral part of breeding, but breeding is not an integral part of molecular biology.     

诱变技术在植物育种中的研究新进展

结合近年来国内外对诱变技术的研究进展 ,综述了主要诱变技术的诱变机理及其在植物育种中的应用 ,并讨论了突变体的选择和鉴定技术等问题     

Cage restraints for rhinoceroses

Captive breeding programs for the rhinoceros can be enhanced by studying their reproductive physiology. To do so requires repetitive manipulations under physically controlled circumstances. To facilitate these procedures, zoos throughout the world have constructed restraint devices, or chutes. Chute designs are usually determined by the space in which they are to be situated and the budget available for their construction. In this study, eight chute designs at seven institutions were compared for efficiency in controlling rhinoceroses during ultrasonography, semen collection, and blood sampling. Procedures were conducted on 16 rhinoceroses of four species: the white rhinoceros (Ceratotherium simum simum), the black (Diceros bicornis), the greater one-horned Asian (Rhinoceros unicornis), and the Sumatran (Dicerorhinus sumatrensis). Chutes were evaluated for dimensions, fabricating materials, procedures to be attempted, and structural features such as shoulder restraints. Permanent, indoor, side-adjustable, pass-through chutes were determined to be the most efficient and convenient type because they saved time and reduced stress on the animals. Zoo Biol 17:343–359, 1998. © 1998 Wiley-Liss, Inc.     

Effect of the early-life nutritional environment on fecundity and fertility of mammals

The early-life developmental environment is instrumental in shaping our overall adult health and well-being. Early-life diet and endocrine exposure may independently, or in concert with our genetic constitution, induce a pathophysiological process that amplifies with age and leads to premature morbidity and mortality. Recently, this has become known as ‘programming’ but is akin to ‘maternal effects’ described for many years in the biological sciences and is defined as any influence that acts during critical developmental windows to induce long-term changes in the organisms'' phenotype. To date, such delayed maternal effects have largely been characterized in terms of susceptibility to cardiovascular or metabolic disease. Here, we review evidence from experimental animal species, non-human primates and man for an effect of the early-life nutritional environment on adult fecundity and fertility. In addition, using a database of pedigree sheep, we also specifically test the hypothesis that being born small for gestational age with or without post-natal growth acceleration directly programmes fertility. We conclude that there is a lack of compelling evidence to suggest pre-natal undernutrition may directly reduce adult fecundity and fertility, but may exert some effects secondarily via an increased incidence of ‘metabolic syndrome’. Possible effects of being born relatively large on subsequent fecundity and fertility warrant further investigation.     

High yield expression and purification of isotopically labelled human endothelin-1 for use in NMR studies

Human endothelin-1 (ET-1) is a potent vasocontractile 21-residue peptide hormone with significant pharmacological importance. An efficient and straightforward expression strategy that enables cost-effective incorporation of stable isotopes is not available thus far. In this report, we describe a cost-effective expression system in Escherichia coli for the production of ET-1 enriched with (15)N and (13)C isotopes. Employing thioredoxin as carrier protein, specific and nearly quantitative cleavage of ET-1 from the fusion was mediated by Factor Xa, and purification to homogeneity (final purity of >95%) was achieved by RP-HPLC. Purified recombinant ET-1 was found to be indistinguishable from the synthetic counterpart as determined by mass spectrometry and NMR spectroscopy. Our expression strategy offers the potential for production of isotopically labeled ET-1 in large (mg) quantities for the purpose of heteronuclear NMR experiments. Moreover, the method devised should be applicable for recombinant expression of small peptides in general.     

The nutritional importance of dietary blood components for reproduction in the tsetse fly, Glossina morsitans

Females of Glossina morsitans morsitans were fed diets of different composition and their performance in terms of survival, fecundity and offspring size, used as a basis for assessing the nutritional importance of the dietary constituents for reproduction. Diets comprised defibrinated bovine blood from which individual components had been removed, or various fractions of bovine blood mixed in different ratios and combinations.Flies fed serum-free diets (comprising saline-washed bovine erythrocytes) failed to reproduce and their ovaries were atrophied. Attempts were made to correct these symptoms by adding serum components to washed erythrocytes. Results showed that serum albumin and lipoproteins were vital for ovarian growth. The erythrocytes in defibrinated bovine blood could be replaced by preparations of haemoglobin. Dialysis against isotonic sodium chloride, removal of gamma globulins, removal of lymphocytes or heating to 55°C for 2 h did not alter the nutritional quality of defibrinated bovine blood. The qualitative importance of dietary albumin associated lipids and lipoproteins for oöcyte growth suggests a specialisation which may be peculiar to viviparous Diptera. Results are discussed in terms of the development of synthetic diets for tsetse.     

应用于家畜育种试验中的组内常相关方差分析

在家畜育种中,不同杂交组合试验的比较,如果采用常规的方差分析方法,由于遗传相关的存在,来自同一家系内的样本,个体之间具有相关性,会产生第一类错误．为此,本文从理论上讨论具有组内常相关性样本的方差分析,导出了新的F检验统计量．并举例在家畜育种试验中的应用．     

Implications of non-linear economic weights for breeding

Summary Relationships were studied theoretically between phenotypic values of selection candidates (parents) and economic worth of the offspring that would belong to production populations. The candidates could include individuals, crosses or clones, and the offspring could be produced either sexually or vegetatively. Cases considered included: three systems for generating production populations [clonal propagation, pair(full-sib)crosses and half-sib crosses]; three economic-worth (profit) functions for individual offspring (linear, intermediate optimum, acceptable versus cull); and independently varying heritabilities for both parents and offspring. The heritabilities were varied in the model against a background of fixed genetic variance. Parental values were considered in terms of phenotypic standard deviations from the population mean, assuming normality. Lower heritabilities and, to a lesser extent, genetic segregation severely damped down the non-linearities of economic worth in relation to measured parental values, such that the linear weightings for traits in a selection index should usually be a good approximation, provided the profit function for individual offspring is monotonic. The economic advantages of corrective mating within a select population may be minimal if both heritabilities are low and the profit functions apply to individual offspring. The economic advantages accruing from genetic uniformity of clones (or crosses between inbreds) in conjunction with non-linear profit functions are strongly dependent on achieving high broad-sense heritabilites, particularly in the offspring (production population).     

Asian elephant (Elephas maximus) milk composition during the first 280 days of lactation

Milk samples (n = 10) taken during the first 280 days of lactation from one Asian elephant were examined for nutrient composition including total solids, protein, fat, ash, α-tocopherol, and retinol levels. Total solids averaged 19.7 ± 2.7% SD (range 15.0–23.3). Percent protein remained fairly stable throughout this portion of lactation and averaged 3.4 ± 0.3% (range 3.0–.4.0). Ash content averaged 0.54 ± 0.03%. Milk fat and fat soluble vitamin levels varied considerably with a suggestion of a cyclic pattern. Fat content of milk averaged 7.6 ± 2.6% (range 3.9–.12.1); α-tocopheral levels averaged 0.33 ± 0.12 μg/ml; and retinol levels averaged 0.46 ± 0.1 μg/ml. © 1994 Wiley-Liss, Inc.