Alternate Selection Indices for Leaf Photosynthetic Rate in Greengram (Vigna radiata [L.] Wilczek) Cultivars

Significant differences were observed for leaf net photosynthetic rate, chlorophyll content, soluble protein content, nitrate reductase activity, stomatal frequency and specific leaf mass among ten greengram cultivars. Leaf net photosynthetic rate had significant positive correlation with soluble protein, nitrate reductase activity, stomatal frequency and specific leaf mass. Leaf net photosynthetic rate had no relationship with leaf chlorophyll content in greengram.     

长输管道用管的选择

长输管道选用何种型式的钢管，应根据钢管的特征、工作状况及使用环境而定，对直径为５０８￣８１３ｍｍ范围内的长输管道的用管情况进行了分析。指出直径小于５０８ｍｍ的管道，当工作压力不高于６．４ＭＰａ时，宜选用高频焊接的直缝管（ＥＲＷ），当工作压力超过６．４ＭＰａ时，可选用无缝钢管；直径在５０８￣８１３ｍｍ或大于８１３ｍｍ的管道，当工作压力低于６．４ＭＰａ时，可采用螺旋焊管，当工作压力超过６．４ＭＰａ时，     

国外肉羊遗传育种研究进展

绵羊群体中存在大量的品种内和品种间的遗传变异。这种变异影响羔羊肉及羊肉生产的性状 ,并提供遗传改良肉质性状的潜力。本文综述活体性状的遗传变异 ,包括生产系统和育种目标 ;品种 /基因型评价 ;遗传参数和选择所致的遗传变化评分 ;信息和改良系统的组织等     

无核优质丰产椪柑新品系——黔阳无核椪柑的选育

1991年从湖南省黔阳县普通柑中选育出来的优良芽变新品系———黔阳无核柑 ,经 8年继代高接繁殖 5代鉴定及多点栽培试验 ,证明其果实稳定无核 (0～ 0 .0 0 1粒 /果 ) ,果形美观 ,肉质脆嫩 ,汁多化渣 ,风味浓郁 ,品质极优。并表现生长旺盛 ,早果、丰产 ,适应性广。该品种已通过湖南省农作物品种审定委员会审定。根据花粉育性研究及人工授粉试验结果 ,初步认为花粉败育及雌性器官 (胚囊 )可能也高度败育是导致其稳定无核的原因     

杂草的形成

杂草的形成是自然选择和人工选择共同作用的结果,其形成机制与杂交,特别是渗入杂交(inerogressire hybridization)有着极为密切的关系。无融合生殖(apomixis)、染色体加倍或减少也都是杂草形成的重要方式。 本文还从自然和人工选择讨论了杂草不同生活习性的形成,并分析了一年生、二年生和多年生杂草对环境的适应和环境对杂草的选择;自花传粉对杂草后代生存和繁衍的重要性;杂草中种子大小的选择意义化及人工选择所产生的拟态种(mimicus)对环境适应的特点。 最后,还讨论了受人工干扰生境的变化和杂草在这变化环境中的变异情况。     

Characterisation of spinosad resistance in the housefly Musca domestica (Diptera: Muscidae)

BACKGROUND: Spinosad, a relatively new, effective and safe pesticide, has been widely used in pest control over the last 10 years. However, different levels of resistance to this insecticide have developed in some insects worldwide. RESULTS: After continuous selection for 27 generations, a strain (SpRR) of the housefly developed 247‐fold resistance to spinosad compared with the laboratory susceptible strain (CSS). The estimated realised heritability (h²) of spinosad resistance was 0.14. There was no significant difference in the LD₅₀ values and slopes between reciprocal progenies F₁ and F₁′, and values of 0.33 (F₁) and 0.30 (F₁′) were obtained for the degree of dominance. Chi‐square analysis from responses of self‐bred (F₂) and backcrosses (BC₁ and BC₂) were highly significant, suggesting that the resistance was probably controlled by more than one gene. Synergists piperonyl butoxide (PBO), diethyl maleate (DEM) and S,S,S‐tributyl phosphorotrithioate (DEF) affected the toxicity of spinosad at a low level, and demonstrated that metabolic‐mediated detoxification was not an important factor in conferring resistance to spinosad in the SpRR strain. CONCLUSION: It was concluded that spinosad resistance in the housefly was autosomal and incompletely dominant, and the resistance was probably controlled by more than one gene. These results provide the basic information for designing successful management programmes for the control of houseflies. Copyright © 2011 Society of Chemical Industry     

Benchmark study on glyphosate-resistant crop systems in the United States. Part 2: Perspectives

A six-state, 5 year field project was initiated in 2006 to study weed management methods that foster the sustainability of genetically engineered (GE) glyphosate-resistant (GR) crop systems. The benchmark study field-scale experiments were initiated following a survey, conducted in the winter of 2005-2006, of farmer opinions on weed management practices and their views on GR weeds and management tactics. The main survey findings supported the premise that growers were generally less aware of the significance of evolved herbicide resistance and did not have a high recognition of the strong selection pressure from herbicides on the evolution of herbicide-resistant (HR) weeds. The results of the benchmark study survey indicated that there are educational challenges to implement sustainable GR-based crop systems and helped guide the development of the field-scale benchmark study. Paramount is the need to develop consistent and clearly articulated science-based management recommendations that enable farmers to reduce the potential for HR weeds. This paper provides background perspectives about the use of GR crops, the impact of these crops and an overview of different opinions about the use of GR crops on agriculture and society, as well as defining how the benchmark study will address these issues.     

Fattening performance and feed source preference of native Awassi lambs fed individually in a cafeteria feeding system

This experiment was conducted to investigate the effect of cafeteria (CF) and conventional (CN) feeding systems on feed intake, feed preferences with respect to voluntary feed source intake, feed conversion rate (FCR) and fattening performance of native Awassi lambs. Sixteen, 3 month old male lambs were used and kept individually for 70 days. Lambs in CF (n = 8) were offered to consume the main ingredients of barley, soybean meal (SBM), sunflower seed meal (SFM) and alfalfa straw, separately, while lambs in CN (n = 8) were fed with a concentrate feed containing 11.34 MJ/kg ME, 17.53% crude protein with the mixture of the same feed sources and alfalfa straw. The initial and final live weights of lambs were similar among groups (P > 0.05). Daily voluntary intake of ash, fat and neutral detergent fiber (NDF) consumptions among groups were quite different during the experiment (P < 0.001). Neither biweekly nor total results of voluntary protein intake between groups were not found statistically significant (P > 0.05). From beginning to the end of the study, the proportional barley intake increased 34 to 43% but reduced for SBM intake from 37 to 23% for the lambs in CF. On the other hand, the SFM intake of lambs did not changed significantly during the experiment and ranged between 2–5%. Lambs in CF did not consume SFM to meet their protein requirement and had 12.5% better total FCR result than the lambs in CN (6.86 and 7.84, respectively) (P > 0.05). The difference of average DWG, total live weight gain, final live weight of lambs in groups were similar (P > 0.05). In conclusion, Awassi lambs in CF can select a diet matching their nutritional requirements from a group of feed sources in response to their growth period when compared to CN system and better FCR result might help to decrease the feed expenses for fattening of native Awassi lambs.     

春秋兼用家蚕品种“恒·丰×富玉”的育成

利用杂交育种及系统选择方法,育成了综合经济性状优良的春秋兼用家蚕新品种恒·丰×富玉。经浙江省家蚕新品种实验室鉴定和农村生产试验表明,该品种孵化、眠起、上蔟齐一,茧丝品质优,万蚕产茧量、万蚕茧层量、5龄1日万蚕茧层量分别比对照品种秋丰×白玉提高2.45%、4.91%、5.22%;一粒茧丝长1158m,解舒丝长996m,洁净96.10分,鲜茧出丝率16.12%,均优于对照品种。日系新品种富玉抗BmNPV感染能力较白玉有明显提高。2010年2月该品种通过浙江省农作物品种审定委员会审定。     

Dimension reduction and variable selection for genomic selection: application to predicting milk yield in Holsteins

Genome‐assisted prediction of genetic merit of individuals for a quantitative trait requires building statistical models that can handle data sets consisting of a massive number of markers and many fewer observations. Numerous regression models have been proposed in which marker effects are treated as random variables. Alternatively, multivariate dimension reduction techniques [such as principal component regression (PCR) and partial least‐squares regression (PLS)] model a small number of latent components which are linear combinations of original variables, thereby reducing dimensionality. Further, marker selection has drawn increasing attention in genomic selection. This study evaluated two dimension reduction methods, namely, supervised PCR and sparse PLS, for predicting genomic breeding values (BV) of dairy bulls for milk yield using single‐nucleotide polymorphisms (SNPs). These two methods perform variable selection in addition to reducing dimensionality. Supervised PCR preselects SNPs based on the strength of association of each SNP with the phenotype. Sparse PLS promotes sparsity by imposing some penalty on the coefficients of linear combinations of original SNP variables. Two types of supervised PCR (I and II) were examined. Method I was based on single‐SNP analyses, whereas method II was based on multiple‐SNP analyses. Supervised PCR II was clearly better than supervised PCR I in predictive ability when evaluated on SNP subsets of various sizes, and sparse PLS was in between. Supervised PCR II and sparse PLS attained similar predictive correlations when the size of the SNP subset was below 1000. Supervised PCR II with 300 and 500 SNPs achieved correlations of 0.54 and 0.59, respectively, corresponding to 80 and 87% of the correlation (0.68) obtained with all 32 518 SNPs in a PCR model. The predictive correlation of supervised PCR II reached a plateau of 0.68 when the number of SNPs increased to 3500. Our results demonstrate the potential of combining dimension reduction and variable selection for accurate and cost‐effective prediction of genomic BV.