Potential biases in screening for plant resistance to insect pests: an illustration with oilseed rape

Breeding to increase crop resistance is a common strategy to decrease damage caused by insect pests, especially in the current context where insecticides are becoming at the same time less accepted by society and less efficient because of widespread pest resistance. The main bottleneck of this strategy is phenotyping. Although simple, high‐throughput methods have been proposed which could be highly useful, they may raise conceptual issues. Using field and laboratory experiments on oilseed rape (Brassica napus) and the pollen beetle (Brassicogethes aeneus syn. Meligethes aeneus), we illustrated possible difficulties with this approach: (i) field screenings might not represent the real attractiveness of the tested genotypes; (ii) plant phenology or spatial organization of the genotypes might bias field screening results; (iii) experiments based on detached plant parts (here, single flower buds or anthers) might not allow to infer the plant–insect relationship of the whole plant. We propose ways to better take these risks into account.     

Economic values and dominant providers of key ecosystem services of wetlands in Beijing,China

This study estimates the economic values of and the dominant contributors to five key ecosystem services of wetlands in Beijing, by using the wetland inventory data in 2014 and economic valuation methods. Results indicate that the 51,434 ha of wetlands in Beijing annually provide 2.07 billion m³ of flood regulation, 944.01 million m³ of water provision, 42,154 tons of chemical oxygen demand (COD) purification, 3.03 PJ of heat absorption, and 9587 ha of habitat. Their economic values are estimated to be 15.89 billion RMB, 1.19 billion RMB, 169 million RMB, 421 million RMB, and 1.08 billion RMB in 2014 (RMB: Chinese currency, US$1 = RMB 6.14), respectively. The total values of five key wetland ecosystem services reach 18.76 billion RMB. In addition, the reservoir and river wetlands in Miyun, Yanqing, Fangshan, Huairou, and Mentougou Districts contribute 78% of key ecosystem services, whereas the urban wetlands in Xicheng, Dongcheng, Haidian, Chaoyang, and Tongzhou Districts more conveniently serve densely local people, hence they should be given particular attentions. In this paper, we develop the valuation methods of wetland ecosystem services, and recommend diversified strategies, regulations, and programs to protect the remaining wetlands in Beijing. This work can also provide a reference for the valuating of wetland ecosystem services for other urban-rural areas.     

双低菜粕高水平替代饲料鱼粉对大黄鱼潜在风险的评估:生长、健康和营养价值

研究从生长、健康和营养价值方面评估了高水平的双低菜粕替代饲料鱼粉对大黄鱼潜在的危害。在鱼粉含量60%的基础饲料（FM）上按照质量分数用双低菜粕分别替代15%（CM15）、30%（CM30）、60%（CM60）和100%（CM100）的鱼粉，配制成5种实验饲料。每种饲料投喂5个网箱的大黄鱼[初重（135.38±1.02）g]，即每个处理5个重复，进行12周的养殖实验。结果表明，当双低菜粕替代水平在15%和30%时，大黄鱼的生长及饲料系数并没有受到显著性的影响。然而，当替代水平高于30%时，大黄鱼的末重和特定生长率均显著降低，而饲料系数显著升高（P < 0.05）。当替代水平达到100%时，大黄鱼摄食率达到最高值而肥满度达到最低值（P < 0.05）。在组织形态方面，大黄鱼摄食双低菜粕替代的饲料后肠道绒毛的弯曲程度减少并且排列更加不规则，而肝细胞则呈现出圆形空泡状并伴随着细胞核的偏移。对大黄鱼骨骼进行X-射线扫描发现，摄食双低菜粕的大黄鱼椎体和头部出现了畸形。在营养价值方面，双低菜粕替代鱼粉并未显著影响大黄鱼背肌的脂肪含量、蛋白含量和氨基酸组成，然而脂肪酸组成受到了显著影响，即N-6系列脂肪酸含量显著升高，而DHA与EPA含量显著降低（P < 0.05）。根据欧洲食品安全局（EFSA）的相关标准，这些营养价值的变化并没有影响大黄鱼作为健康食品的功能。由此可见，高水平（60%和100%）的双低菜粕替代鱼粉对大黄鱼的负面影响主要表现为降低大黄鱼的生长性能、改变肠道和肝脏组织形态，以及影响大黄鱼的骨骼健康。然而，双低菜粕替代鱼粉养殖大黄鱼的肌肉仍然符合人类的膳食要求。因此，双低菜粕替代鱼粉并没有影响大黄鱼作为食用鱼的营养价值。     

浙江饮用水源地浮游动物体积多样性及水质响应

为了解浙江饮用水源地浮游动物体积多样性及对水体综合营养状态（TLIc值）的响应特征，对16个饮用水源地（H1-H8为河网型，K1-K8为水库型）展开了水质参数、浮游动物群落生物体积及其多样性指数的季节调查。结果表明，生物体积密度的季节变化以1月（0.681 mL/L）> 4月（0.443 mL/L）> 10月（0.252 mL/L）> 7月（0.229 mL/L），各季的第一优势种分别为汤匙华哲水蚤（Sinocalanus dorrii）（1月）、晶囊轮虫（Asplanchna sp.）（4月）、粗壮温剑水蚤（Thermocyclops dybowskii）（7月）和长额象鼻溞（Bosmina longirostris）（10月）。河网浮游动物生物体积以轮虫（44.6%）和枝角类（23.4%）为主，水库则以哲水蚤（39.5%）和轮虫（29.0%）为主。夏秋季浮游动物体积多样性指数（P < 0.01）和物种多样性指数（P < 0.05）与lg（浮游动物/浮游植物生物量比率）[lg（ZB:PB）]之间均有显著的相关性，水库中仅浮游甲壳动物体积多样性指数与lg（ZB:PB）之间有极其紧密的相关性（R2=0.77）。与物种多样性指数响应环境效应相比，甲壳动物的体积多样性指数（P < 0.01）能更好地指示夏秋季河网的TLIc值，这归因于甲壳动物个体数（ind./L）转换成了生物体积密度（mL/L）过程中有效信息的放大。     

Smallholder experiences with dairy cattle crossbreeding in the tropics: from introduction to impact

Crossbreeding of indigenous tropical and improved western dairy cattle breeds as tool to improve dairy cattle performance on smallholder farms has been widely advocated, criticised and yet applied. The government of Ethiopia supported this technology for decades but adoption rate is low. Constraints are documented but there is little information about farm level introduction and development of crossbreeding. A total 122 smallholders with mixed crop livestock farms and at least 8 years of successful crossbreeding were interviewed using a pre-tested questionnaire in two contexts in Amhara Regional state in north-western Ethiopia. Crossbreeding initiator was either uncoordinated government extension or a coordinated development project, also implemented with governmental support. Qualitative and quantitative data on farmers’ motivations, crossbreeding introduction, initiator support, breeding adaptation and impacts at farm level were analysed. Results show that even though motives vary between contexts the underlying reason to introduce crossbreeding was economic profit. To be able to introduce crossbreeding support of initiators (e.g. extension) and other farmers was essential. The crossbreeding introduction context had some influence. Governmental actors were the main source of support and supplier of exotic genetics but the farmer network acted as safety net filling gaps of government support. Breeding strategies focused on performance increase. A lack of basic understanding of crossbreeding has been identified. A surprising, probably biased, result was general satisfaction with initiator support and with breeding services. It was challenged by the high proportion of farmers unable to follow a breeding strategy due to insufficient bull and/or semen supply. Crossbreeding changed the smallholder production system to a high input – high output system. Except for crossbred adaptation problems, challenges were ranked context specific and influenced by the initiator. Farmers perceived crossbreeding as success and recommended it. We conclude that farmers can realize income increase with crossbreeding. The complexity of this technology, high initial investment and the need for support services and external production inputs are probable reasons why crossbreeding uptake is low. Improving the availability of semen and/or bulls must be the top priority for breeding service providers to enable farmers to follow a breeding strategy and reach a suitable and sustainable herd performance. Access to investment capital, input supply, strong technical support and market linkages are crucial for successful crossbreeding.     

Enhancing crop legume N2 fixation through selection and breeding

Legume N₂ fixation is variable, but nonetheless is a valuable process in world agriculture. There is great potential to increase the contribution by the crop legumes to the world's supply of soil.N. This will be achieved by (i) increasing the area of legumes sown by farmers; (ii) improved management of the crops in order that the major determinants of productivity, e.g. land area, water availability, are converted to harvested product with maximum efficiency; and (iii) genetic modification of the commonly-grown species to ensure high dependence of the legume crop on N₂ fixation at all levels of productivity. Currently-used methods for measuring N₂ fixation and for assessing heritability and repeatability of N₂ fixation in breeding and selection programs are reviewed. Results from research programs to define genetic variation in N₂ fixation and to enhance N₂ fixation through selection and breeding are presented with particular emphasis on common bean (Phaseolus vulgaris) and soybean (Glycine max).     

Accuracy of genomic selection for age at puberty in a multi‐breed population of tropically adapted beef cattle

Genomic selection is becoming a standard tool in livestock breeding programs, particularly for traits that are hard to measure. Accuracy of genomic selection can be improved by increasing the quantity and quality of data and potentially by improving analytical methods. Adding genotypes and phenotypes from additional breeds or crosses often improves the accuracy of genomic predictions but requires specific methodology. A model was developed to incorporate breed composition estimated from genotypes into genomic selection models. This method was applied to age at puberty data in female beef cattle (as estimated from age at first observation of a corpus luteum) from a mix of Brahman and Tropical Composite beef cattle. In this dataset, the new model incorporating breed composition did not increase the accuracy of genomic selection. However, the breeding values exhibited slightly less bias (as assessed by deviation of regression of phenotype on genomic breeding values from the expected value of 1). Adding additional Brahman animals to the Tropical Composite analysis increased the accuracy of genomic predictions and did not affect the accuracy of the Brahman predictions.