In situ radiometric mapping of soil erosion and field-moist bulk density on cultivated fields

Abstract. Recent developments in in situγ ray spectrometry offer a new approach to measuring the activity of radionuclides such as ¹³⁷Cs and ⁴⁰K in soils, and thus estimating erosion or deposition rates and field moist bulk density (ρ_m). Such estimates would be rapid and involve minimal site disturbance, especially important where archaeological remains are present. This paper presents the results of a pilot investigation of an eroded field in Scotland in which a portable hyper pure germanium (HPGe) detector was used to measure γ ray spectra in situ. The gamma (γ) photon flux observed at the soil surface is a function of the ¹³⁷Cs inventory, its depth distribution characteristics and ρ_m. A coefficient, Q_Cs, derived from the forward scattering of ¹³⁷Cs γ ray photons within the soil profile relative to the ¹³⁷Cs full energy peak (662 keV), was used to correct the in situ calibration for changes in the ¹³⁷Cs vertical distribution in the ploughed field, a function of tillage, soil accumulation and ρ_m. Based on only 8 measurements, the agreement between in situγ ray spectrometry and soil sample measurements of ¹³⁷Cs inventories improved from a non significant r²=0.05 to a significant r²=0.62 (P<0.05). Erosion and deposition rates calculated from the corrected in situ¹³⁷Cs measurements had a similarly good agreement with those calculated from soil cores. Mean soil bulk density was also calculated using a separate coefficient, Q_K, derived from the forward scattering γ photons from ⁴⁰K within the soil relative to the ⁴⁰K full energy peak (1460 keV). Again there was good agreement with soil core measurements (r²=0.64; P<0.05). The precision of the in situ¹³⁷Cs measurement was limited by the precision with which Q_Cs can be estimated, a function of the low ¹³⁷Cs deposition levels associated with the weapons testing fallout and relatively low detector efficiency (35%). In contrast, the precision of the in situ ρ_m determination was only limited by the spatial variability associated with soil sampling.     

Genetic Engineering Approaches to Pig Production*

Modern biotechnology promises a number of new applications in animal breeding and production. Although conventional pig breeding has achieved a high level of efficiency and productivity numerous problems have been encountered with animal health and the loss of meat quality. Selection based on phenotypic performance data of individual animals does not take into account the importance of specific genes and their relevance within a complex regulatory system. In most cases it is therefore difficult to trace back the genetic origins of clinically important disorders. The application of genetic engineering techniques in pig production will facilitate diagnosis, improvement of productivity, and animal health by allowing direct genetic manipulation. Attention must be focussed on the physical and genetic analysis of the procine genome. The isolation and characterisation of genes, DNA-markers, polymorphic DNA-fragments, and their chromosomal assignment will be important prerequisites and tools for the elucidation of genetic disorders. Especially the detection of heterozygous carriers of recessive disorders and their elimination from the breeding stock will increase selection accuracy and decrease the generation intervals. But also the rapid and simple detection of infectious diseases, which is sometimes difficult if not impossible at present, will improve animal health and welfare. Although the production of transgenic animals either by DNA-microinjection into zygotes or the use of embryonal stem cells manipulated in vitro is less straightforward than DNA-based diagnosis it will play an important role in the direct manipulation of the porcine genome and genes. Breeding programmes including the use of transgenic livestock have already been developed. There is no doubt that genetic engineering has reached a degree of practical feasibility, allowing it to play an important role in pig breeding in particular and animal production in general.     

Genetic Analysis and Mapping of TWH Gene in Rice Twisted Hull Mutant

A mutant with twisted hulls was found in a breeding population of rice (Oryza sativa L.). The mutant shows less grain weight and inferior grain quality in addition to twisted hulls. Genetic analysis indicated that the phenotype of mutant was controlled by a single recessive gene (temporarily designated as TWH). To map the TWH gene, an F2 population was generated by crossing the twh mutant to R725, an indica rice variety with normal hulls. For bulked segregant analysis, the bulk of mutant plants was prepared by mixing equal amount of plant tissue from 10 twisted-hull plants and the bulk of normal plants was obtained by pooling equal amount tissue of 10 normal-hull plants. Two hundred and seven pairs of simple sequence repeat (SSR) primers, which are distributed on 12 rice chromosomes, were used for polymorphism analysis of the parents and the two bulks. The TWH locus was initially mapped close to the SSR marker RM526 on chromosome 2. Therefore, further mapping was performed using 50 pairs of SSR primers around the marker RM526. The TWH was delimited between the SSR markers RM14128 and RM208 on the long arm of chromosome 2 at the genetic distances of 1.4 cM and 2.7 cM, respectively. These results provide the foundation for further fine mapping, cloning and functional analysis of the TWH gene.     

水稻苗期耐冷性的QTL定位分析

为水稻苗期耐冷性QTL定位克隆研究提供实验素材,以213个IR24/Asominori重组自交家系(RIL)为作图群体,并以141个SSR标记构建的分子连锁图谱为基础,结合苗期低温处理后亲本和213个RILs的苗期死苗率,运用QTL IciMapping 4.0软件进行水稻苗期耐冷性QTL检测及其遗传效应分析。结果表明:在第6、第11和第12染色体上检测到3个苗期耐冷性QTL,分别命名为qCTS-6、qCTS-11和qCTS-12。这3个QTL的LOD值分别为3.194 3、4.688 2和3.797,对应表型变异的解释率分别为5.662 7%、8.549 6%和12.787 7%,且抗性等位基因均来自苗期耐冷亲本Asominori。     

番茄SSR遗传连锁图谱的构建及每序花数性状的QTL定位

以每序花数性状差异显著的栽培番茄与野生醋栗番茄杂交产生的F2为作图群体，应用SSR标记构建了番茄的遗传连锁图谱。图谱共包含120个标记,总长度为879．1cM，标记平均间距7．33cM。利用区间作图法在第2和第5染色体上检测到2个与每序花数有关的QTLs，其贡献值分别为5．22％和8．39％。     

多年生黑麦草叶片长度数量性状位点(QTLs)研究

选择固定有益等位基因,研究多年生黑麦草叶片长度数量性状位点,结果表明:与叶长最为相关的3个标记所表达的变异占表型总变异的50.9%(r2);在选择中如能将这3个标记最优化地组合在一起,其综合共同作用有望使叶片长度延长和缩短26 mm;鉴于供试材料在最初3个世代的群体选择中所估测到叶片长度的遗传力为0.32,这样在今后的选择工作中,即使只使用现有的两个标记,其效果亦优于传统的表型选择法.     

扩增片段长度多态性（AFLP）在动物遗传育种中的应用进展

AFLP是一种新的分子遗传标记技术，它结合了RFLP和PCR技术的优点，具有RFLP的稳定性和PCR的高效性，被称为“最有威力的分子遗传标记”或“下一代分子标记”。相对于国外而言，我国在这方面的研究还比较少。本文综述了扩增片段长度多态性(AFLP)这种遗传标记的原理、技术特点、技术发展及其在动物遗传多样性、种质鉴定、遗传图谱构建、基因定位和标记辅助育种等研究中的应用。     

Power of a genome scan to detect and locate quantitative trait loci in cattle using dense single nucleotide polymorphisms

There is increasing use of dense single nucleotide polymorphisms (SNPs) for whole‐genome association studies (WGAS) in livestock to map and identify quantitative trait loci (QTL). These studies rely on linkage disequilibrium (LD) to detect an association between SNP genotypes and phenotypes. The power and precision of these WGAS are unknown, and will depend on the extent of LD in the experimental population. One complication for WGAS in livestock populations is that they typically consist of many paternal half‐sib families, and in some cases full‐sib families; unless this subtle population stratification is accounted for, many spurious associations may be reported. Our aim was to investigate the power, precision and false discovery rates of WGAS for QTL discovery, with a commercial SNP array, given existing patterns of LD in cattle. We also tested the efficiency of selective genotyping animals. A total of 365 cattle were genotyped for 9232 SNPs. We simulated a QTL effect as well as polygenic and environmental effects for all animals. One QTL was simulated on a randomly chosen SNP and accounted for 5%, 10% or 18% of the total variance. The power to detect a moderate‐sized additive QTL (5% of the phenotypic variance) with 365 animals genotyped was 37% (p < 0.001). Most importantly, if pedigree structure was not accounted for, the number of false positives significantly increased above those expected by chance alone. Selective genotyping also resulted in a significant increase in false positives, even when pedigree structure was accounted for.