华北油松林油松种群的空间分布格局

以内蒙古黑里河、北京松山及山西太岳山的油松林监测样地为对象,分析了油松(Pinus tabulaeformis)种群的空间分布格局,探讨了油松不同生长阶段(幼树、小树和大树)之间的空间关系.结果表明,黑里河、松山、太岳山样地中胸径≥1cm的油松种群密度分别为1741、467和722株/hm~2.3块样地中油松种群具有一致的空间分布格局,主要呈聚集分布.随着油松种群发育(幼树→小树→大树),聚集强度逐渐减弱甚至趋向于随机分布,一定程度上体现了油松种群的生存策略及其适应机制.不同生长阶段之间的空间关联性受油松植株大小影响,大小差异越小彼此间的空间关联性则越大.     

鲤正、反交F2群体的AFLP遗传图谱构建及其QTL定位

以高代选育的荷包红鲤和兴国红鲤的正、反交F2群体为材料,利用AFLP标记构建了鲤正、反交群体的遗传图谱,并进行了生长相关性状的QTL定位。在正交群体中,14对AFLP引物共产生542个多态性标记,其中325个标记符合3∶1的孟德尔分离比例,利用其构建的遗传图谱涵盖50个连锁群,图谱总长度3 676.1 cM,并获得了与全长、体长、体高、尾柄长和尾柄高5个生长性状相关的17个QTL,可解释表型变异的1.66%~70.49%;在反交群体中,14对AFLP引物共产生605个多态性标记,其中333个标记符合3∶1孟德尔分离比例,构建的遗传图谱也涵盖50个连锁群,图谱总长度3 943.1 cM,获得了与体重、全长、体长、体高和尾柄长5个生长性状相关的15个QTL,可解释表型变异的1.58%~63.89%。还对正、反交群体构建的遗传图谱及QTL定位差异及结果进行了初步分析和探讨。     

鲤易捕性状选育群体不同世代微卫星分析

用30对微卫星引物对易捕性状人工选育鲤(Cyprinus carpio)的4个连续世代共计154个个体进行了遗传分析。4个世代(F1-F4)的平均等位基因数分别为7.7619、6.9189、5.0889、4.6667;平均多态信息含量分别为0.6215、0.7512、0.7314、0.7431;平均观测杂合度分别为0.7730、0.7135、0.7593、0.7196,人工定向选育已对群体的多样性造成了影响。Hardy-Weinberg平衡的卡方检验及F-检验数据显示人工累代选育已经使群体的遗传结构发生了变化,并开始趋于稳定,表现为偏离平衡的位点逐代增加,相邻世代之间遗传分化系数逐代减小。FST平均值0.0995提示出选育群体已处在中等分化水平,有90%的遗传变异来自于群体内个体间。遗传距离及遗传相似性结果显示随着选育世代的增加,世代之间遗传距离越来越小,遗传相似性越来越大,但与理论值仍有差距,说明还有育种潜力,应继续保持遗传效应,确保育种成功。     

K94复合活菌剂对蛋鸡产蛋性能、饲料消化率和盲肠菌群的影响

240只60周龄的海赛克斯褐壳蛋鸡用于作K94的应用效果试验。试验开始2周后，试验组（基础日粮中添加1％K94）产蛋率提高7．85％，对照组（添加无活菌的1％K94）则降低2．34％。日粮中未添加维生素后．试验组产蛋率下降28．15％，对照组则下降38．49％。重新添加维生素后，试验组和对照组产蛋率都迅速回升，但试验组回升速度比对照组快。整个试验期（9周），试验组产蛋率和枚蛋重都明显高于对照组；料蛋比明显比对照组低。饲喂K949周后，与对照组比较，试验组采食量增加8．01％，饲料干物质（DM）和粗蛋白（CP）消化分别提高14．79％和18．49％；盲肠内容物中大肠杆菌明显减少，而厌氧乳杆菌、梭状芽胞杆菌以及双歧杆菌数量明显增多。结果表明，K94能明显改善盲肠微生态环境，提高饲料消化率，从而提高蛋鸡的产蛋性能，改善日粮中维生素不足对产蛋性能的影响。     

Breed, gender and neutering status of British dogs with anal sac gland carcinoma

This study details the breed, gender and neutering status of a large cohort of British canine patients suffering from histologically confirmed anal sac gland carcinoma. Estimates of the relative risk for the development of this disease attributable to these factors are calculated. To reduce the impact of sampling errors, cases were selected from veterinary histopathology laboratories rather than referral hospital databases, and multiple estimates of the general British canine population were used. The weaknesses of the statistical assumptions made are discussed. There was no evidence to support a gender predisposition for the development of this condition. English cocker spaniels are significantly over‐represented, with a mean relative risk estimate of 7.3. The mean relative risk estimate associated with being neutered was 1.4; the effect of neutering appeared to be more significant in male dogs compared with that in female dogs.     

Isozyme and amplified fragment length polymorphisms fromCephalosporium maydis in Egypt

Isoenzyme and amplified fragment length polymorphisms (AFLP) variation within a set of 48 isolates ofCephalosporium maydis was characterized. These isolates included ten cultures that have served as standards in the Egyptian maize resistance breeding program and 38 additional strains collected from 11 governates in Egypt during the 1997 growing season. Eight isozymes also were tested, but only five (acid phosphatase, fumerase, gtucose 4-phosphate isomerase, isocitrate dehydrogenase, and malate dehydrogenase) produced identifiable bands and all five of these enzymes were monomorphic. Sixty-eight AFLP primer-pair combinations were used and 865 bands were scored, of which 288 (33%) were polymorphic and could be used to discriminate four distinct subgroups, or lineages. Representatives from only two of the four lineages are included in the set of ten strains that has been used to challenge new lines in the Egyptian maize breeding program. From among these 68 primer-pair combinations, we identified a set of four AFLP primer-pairs that were strongly correlated (Pearson‘sr > 0.85) with the full data set that can be used as markers to determine the distribution of these lineages and to identify new lineages in field populations.     

The use of allozymes at three life stages influences genetic variation analysis and clustering in Cicer arietinum germplasm collections

Levels of genetic variation using 6 enzyme systems for a total of 11 interpretable loci were examined in chickpea (Cicer arietinum) originating from 9locations in Bangladesh. The measurement of genetic variation at enzyme loci was carried out on the seed embryo, on the early leaves of seedlings and on the mature leaves at the vegetative stage. A total of 592individuals, including 240 seeds, 200 seedlings and152 mature leaves were investigated. Using electrophoretic data, chickpea was found to express higher percentages of polymorphic loci at the seed stage (36–64%) than at seedling (22–56%) or the vegetative stage (11–44%). The proportion of mean number of alleles and the average mean observed heterozygosity also were higher at the seed stage when compared to the seedling and vegetative stages. Unique alleles were absent, and only differences infrequencies could be noticed. Positive values of the fixation index were noted for pgm-1 and 6pg-1 for all stages and in both mnr loci for the seed embryo's. A trend towards lower genetic distances of all possible pairs of populations could be observed when comparing those of seed embryo's with seedlings or mature leaves. This trend was even more pronounced when pooling the data of 9 populations into their 3regions. Slight differences in genetic distances caused a separative clustering of population 3 at seed embryo, of population 2 at seedling and of population5 at vegetative stages. It is suggested that careful examination of enzyme polymorphisms at different developmental stages is a prerequisite before drawing conclusions on the genetic distance between germplasm collections from different origins since small differences in the data entry for clustering results in ties that may affect tree topologies. This revised version was published online in July 2006 with corrections to the Cover Date.     

不同林龄杨树人工林对土壤微生物状况和酶活性的影响

对文安县不同林龄的中林-46（Zhonglin-46）杨人工林的土壤微生物和酶活性进行了测定分析。结果表明不同林龄的土壤微生物和土壤酶活性均存在差异,0~20cm的表土层明显高于20~40cm的亚表层和40~60cm深层。在测定时间内（2006年4月—11月）各个林龄的土壤微生物总数在春季较高,夏季较低,秋季又增高,总体上表现为高-低-高的变化。土壤微生物和酶活性之间表现出较高的相关性,土壤微生物的总数和酶活性随着取样深度的增加均表现为逐渐降低。     

Linkage disequilibrium and genomic scan to detect selective loci in cattle populations adapted to different ecological conditions in Ethiopia

Despite the wide range of observed phenotypic diversities and adaptation to different ecological conditions, little has been studied regarding the genetics of adaptation in the genome of indigenous cattle breeds of developing countries. Here, we investigated the linkage disequilibrium (LD) and identified the subset of outlier loci that are highly differentiated among cattle populations adapted to different ecological conditions in Ethiopia. Specifically, we genotyped 47 unrelated animals sampled from high‐ versus low‐altitude environments using a Bovine 50K SNP BeadChip. Linkage disequilibrium was assessed using both D′ and r² between adjacent SNPs. We calculated F_ST and heterozygosity at different significance levels as measures of genetic differentiation for each locus between high‐ and low‐altitude populations following the hierarchical island model approach. We identified 816 loci (p < 0.01) showing selection signals and are associated with genes that might have roles in local adaptation. Some of them are associated with candidate genes that are involved in metabolism (ATP2A3, CA2, MYO18B, SIK3, INPP4A, and IREB2), hypoxia response (BDNF, TFRC, and PML) and heat stress (PRKDC, CDK1, and TFDC). Average r² and D′ values were 0.14 ± 0.21 and 0.57 ± 0.34, respectively, for a minor allele frequency (MAF) ≥ 0.05 and were found to increase with increasing MAF value. The outlier loci identified in the studied Ethiopian cattle populations indicate the presence of genetic variation produced/shaped by adaptation to different environmental conditions and provide a basis for further validation and functional analysis using a reasonable sample size and high‐density markers.     

多种群竞争遗传算法及其性能分析

在指出传统遗传算法收敛中所存在的收敛速度慢及局部收敛问题的基础上,引入了一种新的改进遗传算法——多种群竞争遗传算法。该算法以种群间竞争为基础,不断淘汰相似个体,并不断补充新个体,增加种群的多样性,以提高收敛速度。最后,用一个典型的测试函数对传统遗传算法和多种群遗传算法进行测试,结果表明多种群遗传算法的性能优于传统遗传算法。