Varietal Differences in Development of Maize (Zea mays L.) Seedlings on Compacted Soils

Differences among open-pollinated tropical maize ( Zea mays L.) varieties in seedling development and establishment on compacted soils were studied. Soil dry density was used as an index of compaction. Three soil compaction levels and 12 traits associated with development and establishment of maize seedlings were investigated. A control (without compaction) was also included. Varietal differences were observed for most traits measured. Genetic differences for seedling development on compacted soil were detected. Varietal differences contributed about three times the contribution of compaction to total variability in the traits. Better seedling development and performance were obtained in moderately compacted soil than in the control. Shoot length, shoot dry weight and per cent dry matter in roots were good indicators of the tolerance of maize seedlings to compaction. A physiological strategy for maize seedling establishment on compacted soil was proposed. The implications of the results for seed testing were also highlighted. It was concluded that consideration should be given to the genotype of maize destined for use in ecologies prone to high soil densities. All varieties of maize grown in an agroecological zone could be screened to identify genotypes tolerant of higher soil densities. The seeds could then be multiplied and distributed to farmers.     

Effect of the number of intercrosses on grain yield in basic rice synthetic populations

The effect of 0, 1, 2, 3 and 4 intercross cycles using genetic male sterility on the mean yield and genetic variability of the CNA 5 irrigated rice synthetic population was assessed studying 300 S_0:2 (1998/99) and S_0:3 (1999/00) families grown in two locations (Lambari, MG and Goianira, GO). Each intercross was investigated using a 8 × 8 triple lattice design experiment containing 60 families and four control cultivars. Five experiments were carried out per location and generation, totaling 20 experiments. Individual, combined over locations, combined over generations and combined over locations and generations analyses of variance were performed. Linear regression equations were fitted to data of each location and generation as well as, genetic and phenotypic parameters were estimated. An average increase of 3.91% in grain yield was obtained with the increase in the number of intercrosses. However, when genetic gains obtained from selection of the five and ten highest yielding families were considered, negative b estimates were always obtained, suggesting a tendency of gain increase reduction with the increase in the number of intercrosses. This was confirmed by the analysis of the means of the best families, since increases in the number of intercrosses did not result in selection of families with greater mean grain yield. The estimates of the genetic variances and heritabilities did not suggest an increase in genetic variability with the increase in intercross cycles. Therefore, carrying out intercrosses on the base population did not improve the results of the irrigated rice recurrent selection program. This revised version was published online in August 2006 with corrections to the Cover Date.     

选择产蛋量七个世代蛋壳及蛋品质的相关反应

以北京白鸡Ⅲ系七世代选择群和基础群为材料,估计选择产蛋量七个世代对蛋壳及蛋品质产生的相关反应.结果表明,经七个世代选择,产蛋量、蛋重、蛋白高度和哈夫单位都有所提高,而蛋壳厚度和蛋比重有一定程度下降.估计蛋壳厚度、蛋白高度和哈夫单位的遗传力分别是0.159 5、0.017 8和0.099 4.产蛋量与蛋白高度、哈夫单位和蛋壳厚度呈负遗传相关.选择产蛋量使蛋壳品质发生负向相关反应.     

Variation in Nicotine Content of Cultured Cell Lines of Nicotiana Species and their Somatic and Sexual Hybrids

Several Nicotiana species, their intergeneric sexual and somatic hybrids were compared for their in vitro growth rate and nicotine content. Cell yield on a dry weight basis and HPLC analysis of their nicotine content revealed a very high variation within each cell line from parental, sexual and somatic hybrids for the two traits analyzed. The trigeneríc sexual hybrids (N. rustica × N. debneyi) × N. tabacum and only two of the N. rustica × N. tabacum somatic hybrid lines show a positive heterosis in nicotine content in vitro The in vitro growth rate and nicotine content did not demonstrate a statistically significant correlation.     

利用微卫星遗传标记估计金华猪个体间的亲缘关系

本研究采用微卫星标记多重扩增结合荧光标记检测技术,对金华猪Ⅰ系保种群中的120头猪的29个微卫星位点的基因型进行了检测,由检测结果可见,金华猪的基因纯合率较高,用SPSS软件对其中的72头金华猪个体间的亲缘关系进行聚类,在距离系数为8．147的水平上将这些猪聚成10大类。个体间的亲缘关系清楚可见,除个别猪外,与系谱资料的记录结果基本相符。根据聚类结果对5头系谱不明的猪进行了亲缘关系分析,结果是97-288与 98-104接近全同胞。23与784、99-542、K89等4头猪间的亲缘关系接近半同胞,302、382这两只猪间及与其他猪间几乎无亲缘关系。     

昆山麻鸭微卫星DNA标记监测选种效果的研究

利用12个微卫星标记分析了昆山麻鸭高产系F0代和F1代遗传多样性,监测选种效果。结果表明12个微卫星座位共检出83个等位基因,基因频率分布在0.0077～0.5859,平均每对引物扩增出8.3个等位基因。F0代微卫星的平均杂合度为0.7489,平均多态性含量0.7125;F1代为0.7668和0.6901。表明昆山麻鸭种群的群体遗传变异已趋于稳定。     

短季棉主要农艺性状的遗传分析

选用5个早熟不早衰的短季棉品种和5 个早衰的短季棉品种进行部分双列杂交。通过对亲本、F1 和F2 代分别于2001 年和 2002 年两年田间试验研究。结果表明:子棉产量、皮棉产量和衣分3个性状以显性效应为主,其次为加性效应,同时还存在极显著的加性上位性与环境的互作效应,单铃重和成铃数以显性效应为主;与早熟有关的诸性状,生育期、始花期、铃期和果枝始节4个性状以加性效应为主,其次为显性效应,霜前花率以显性效应×环境互作效应为主,同时存在显著的加性上位效应,落叶株率以加性与加性互作上位性为主,落叶指数以加性效应为主;与纤维品质有关的诸性状,2.5%跨长、比强度、伸长率3个性状以加性效应为主,其次为显性效应,同时还存在着加性、上位性与环境的互作效应;同时还研究了产量、早熟性和纤维品质各性状之遗传和表型相关关系。     

单核苷酸多态性(SNP)的研究进展和应用

单棱苷酸多态性(SNP)是最新发展起来的第三代分子标记，具有密度高、双等位基因、易实现自动化检测等优点。本文重点介绍了SNP的概念、特点、分析检测技术以及SNP的应用。     

红河大翼橙的遗传多样性分析*

 在100个随机引物中选取了13个可扩增出多态性产物的引物,对红河大翼橙6个居群的120个体进行了ISSR扩增,试验结果表明,红河大翼橙居群之间表现出较高水平的遗传分化,为柑橘遗传资源利用和保护方面提供了分子水平上的依据。     

基于遗传算法的变压边力模型及其在回弹控制中的应用

为尽可能地减少回弹对冲压件质量的影响，采用Hughes和Liu提出的适用于非线性的二维壳单元来开发冲压和回弹的计算程序．在准确预测回弹量的前提下，提出了一种基于遗传算法的变压边力模型用于回弹控制．与常压边力模型相比，回弹得到很好控制，能够得到更好的成型结果．