Impact of climate change on maize yield in China from 1979 to 2016

Climate change severely impacts agricultural production, which jeopardizes food security. China is the second largest maize producer in the world and also the largest consumer of maize. Analyzing the impact of climate change on maize yields can provide effective guidance to national and international economics and politics. Panel models are unable to determine the group-wise heteroscedasticity, cross-sectional correlation and autocorrelation of datasets, therefore we adopted the feasible generalized least square(FGLS) model to evaluate the impact of climate change on maize yields in China from 1979–2016 and got the following results:(1) During the 1979–2016 period, increases in temperature negatively impacted the maize yield of China. For every 1°C increase in temperature, the maize yield was reduced by 5.19 kg 667 m–2(1.7%). Precipitation increased only marginally during this time, and therefore its impact on the maize yield was negligible. For every 1 mm increase in precipitation, the maize yield increased by an insignificant amount of 0.043 kg 667 m–2(0.014%).(2) The impacts of climate change on maize yield differ spatially, with more significant impacts experienced in southern China. In this region, a 1°C increase in temperature resulted in a 7.49 kg 667 m–2 decrease in the maize yield, while the impact of temperature on the maize yield in northern China was insignificant. For every 1 mm increase in precipitation, the maize yield increased by 0.013 kg 667 m–2 in southern China and 0.066 kg 667 m–2 in northern China.(3) The resilience of the maize crop to climate change is strong. The marginal effect of temperature in both southern and northern China during the 1990–2016 period was smaller than that for the 1979–2016 period.     

‘哈伯’南天竹组织培养和快速繁殖

为建立‘哈伯’南天竹组织培养和种苗繁育技术体系,以半木质化带芽茎段为外植体材料开展植株再生研究。通过观察对比试验法、L₉(3⁴)正交试验设计完全随机法、极差分析、显著性检验、LSD多重比较,探讨了‘哈伯’南天竹组培的最适培养基配方。试验结果表明：最佳诱导培养基为MS + 6-BA 2.0 mg/L + IBA 0.1 mg/L +蔗糖30 g/L,诱导萌动率71.77%,成活率85.51%;最佳增殖培养基为WPM +6-BA 1.5 mg/L + IBA 0.01 mg/L + 蔗糖30 g/L,增殖系数6.3;最佳生根培养基为1/2 MS+ IBA 0.5 mg/L + NAA 1.0 mg/L + 蔗糖20 g/L + AC 0.2 g/L,生根率97.63%;试管苗移入泥炭土:珍珠岩=3:2(V/V)混合基质中,移栽成活率96.67%。该试验建立了高效稳定的组培快繁技术体系,得到的组培苗后代能够稳定的保持母本优良性状,为工厂化育苗提供了技术支撑。     

“一带一路”背景下陕西茶叶跨境电商发展路径研究

陕西作为丝绸之路的发源地，以其有利的自然生态条件和区域产业结构，形成了以茶叶为主导的产业发展格局。目前，陕西省茶叶出口规模不大，市场占有率较低。在“一带一路”倡议的推动下，陕西省茶叶出口至沿线国家的潜力较大，未来将逐步呈上升态势。研究了“一带一路”背景下陕西茶叶跨境电商市场发展现状和存在的问题，提出陕西茶叶跨境电商发展路径，通过借力跨境电商平台、开拓国际市场、稳固绿茶品牌、布局海外仓解决出口难的问题，以及完善跨境电商法律秩序，拓展陕西茶叶跨境电商发展路径。      

乡土物种补播对青藏高原高寒草甸群落稳定性的影响

为了探究高寒草甸天然草地补播乡土物种对草地群落稳定性的影响，本试验以垂穗披碱草（Elymus nutans）、异针茅（Stipa aliena）、中华羊茅（Festuca sinensis）、溚草（Koeleria cristata）、星星草（Puccinellia tenuiflora）、扁蓿豆（Melissitus rutenica）、冷地早熟禾（Poa crymophila）为试验材料，设置5种混播组合，于2017年在青海省贵南县天然草地上进行补播。试验采用方差比率法（Variance ratio，VR）、M.Godron贡献定率法（Contribution law）以及生物量稳定性分析方法，结果表明：5种组合补播后使得群落联结性降低、生物量稳定性增大，群落整体稳定性增强，正向着稳定方向发展；5种组合中，组合D （扁蓿豆+星星草+垂穗披碱草+异针茅+溚草）的生物量稳定性最大，是对草地恢复最有效的物种组合。本试验筛选出了对草地生态修复最有效的物种组合，为草地保护及利用提供了科学依据。     

不同杀青方式龙井茶自动化连续生产线加工工艺探讨

文章剖析了不同杀青方式龙井茶自动化连续生产线的设备配置和工艺流程,对生产线的龙井茶品质进行感官评价,为龙井茶生产线推广应用提供借鉴。     

Screening and Verification of Low Nitrogen Tolerant and Nitrogen Sensitive Cotton Germplasm

[Objective] The aim of this study is to evaluate nitrogen efficient cotton germplasms and improve nitrogen use efficiency. [Method] Eighty cotton germplasms were selected and evaluated in the hydroponic experiment under low (0.25 mmol·L^－1) and high (5 mmol·L^－1) nitrogen concentration. Different traits for screening were identified and nitrogen use efficiency types were classified. Field experiments were also performed for comparison and confirmation of the identified germplasms. [Result] The results showed that there were significant differences in the total plant dry matter, shoot nitrogen accumulation and nitrogen absorption efficiency in cotton germplasms at the two nitrogen levels. Based on coefficient of variation, principal component analysis and correlation, six traits including total plant dry matter, shoot dry matter, root dry matter, total nitrogen accumulation, shoot nitrogen accumulation and nitrogen absorption efficiency were used as screening indicators. According to the Heatmap clustering analysis and the nitrogen efficiency comprehensive index, two germplasms (Lu05R59 and CCRI 69) were identified as low nitrogen tolerant and nitrogen efficient, and two germplasms (Coker 201 and Xinluzhong 30) as low nitrogen sensitive and nitrogen inefficient. The results of field experiment were consistent with the results of the hydroponic culture at the seedling stage. [Conclusion] It was finally determined that Lu05R59 and CCRI 69 were the low nitrogen tolerant and nitrogen efficient germplasms, and Coker 201 and Xinluzhong 30 were low nitrogen sensitive and nitrogen inefficient germplasms. The results of these studies provide the possibility for screening and rapid identification of nitrogen use efficiency in cotton at the seedling stage, and provide the ideal materials and theoretical basis for further study of cotton nitrogen efficient.     

Regulatory role of l-proline in fetal pig growth and intestinal epithelial cell proliferation

l-proline (Pro) is a precursor of ornithine, which is converted into polyamines via ornithine decarboxylase (ODC). Polyamines plays a key role in the proliferation of intestinal epithelial cells. The study investigated the effect of Pro on polyamine metabolism and cell proliferation on porcine enterocytes in vivo and in vitro. Twenty-four Huanjiang mini-pigs were randomly assigned into 1 of 3 groups and fed a basal diet that contained 0.77% alanine (Ala, iso-nitrogenous control), 1% Pro or 1% Pro + 0.0167% α-difluoromethylornithine (DFMO) from d 15 to 70 of gestation. The fetal body weight and number of fetuses per litter were determined, and the small and large intestines were obtained on d 70 ± 1.78 of gestation. The in vitro study was performed in intestinal porcine epithelial (IPEC-J2) cells cultured in Dulbecco''s modified Eagle medium-high glucose (DMEM-H) containing 0 μmol/L Pro, 400 μmol/L Pro, or 400 μmol/L Pro + 10 mmol/L DFMO for 4 d. The results showed that maternal dietary supplementation with 1% Pro increased fetal weight; the protein and DNA concentrations of the fetal small intestine; and mRNA levels for potassium voltage-gated channel, shaker-related subfamily, member 1 (Kv1.1) in the fetal small and large intestines (P < 0.05). Supplementing Pro to either gilts or IPEC-J2 cells increased ODC protein abundances and polyamine concentrations in the fetal intestines and IPEC-J2 cells (P < 0.05). In comparison with the Pro group, the combined administration of Pro and DFMO reduced the expression of ODC protein and spermine concentration in the fetal intestine, as well as the concentrations of putrescine, spermidine and spermine in IPEC-J2 cells (P < 0.05). Meanwhile, the percentage of cells in the S-phase and the mRNA levels of proto-oncogenes c-fos and c-myc were increased in response to Pro supplementation, whereas depletion of cellular polyamines with DFMO increased tumor protein p53 (p53) mRNA levels (P < 0.05). Taken together, dietary supplementation with Pro improved fetal pig growth and intestinal epithelial cell proliferation via enhancing polyamine synthesis.     

桃蚜电压门控钠离子通道基因cDNA克隆及其生物信息学分析

克隆获得桃蚜电压门控钠离子通道基因cDNA序列，明确钠离子通道的典型特征，为研究桃蚜抗性分子机理奠定基础。采用实验技术主要有RT-PCR和PCR，克隆桃蚜钠离子通道基因cDNA序列，利用相关软件对其序列进行生物信息学分析。克隆得到两段cDNA序列MpNa_v-1（NCBI登录号：MN124170）和MpNa_v-2（NCBI登录号：MN176136）。MpNa_v-1长度为2945 bp，包括2877 bp的完整开放阅读框，共编码958个氨基酸；MpNa_v-2长度为3546 bp，包括3486 bp的完整开放阅读框，共编码1161个氨基酸。MpNa_v-1和MpNa_v-2共同组成桃蚜的钠离子通道α亚基，MpNa_v-1包含同源结构域Ⅰ和同源结构域Ⅱ，MpNa_v-2包含同源结构域Ⅲ和同源结构域Ⅳ。同源比对发现，桃蚜与豌豆蚜和高粱蚜钠离子通道基因相似度分别高达97.67%和97.65%，所克隆序列包含昆虫钠离子通道α亚基典型特征，具有MFM模块，并含有蚜虫类钠通道特有模块DENS。成功地克隆桃蚜钠离子通道基因，为阐明其对拟除虫菊酯类药剂产生靶标抗性的分子机制奠定基础。     

籽用南瓜育种研究进展

南瓜种子含有丰富的营养成分，具有较高的保健价值。我国籽用南瓜产业规模逐年扩大，但目前种质创制和新品种 选育尚有待开展较为系统的研究。本文从籽用南瓜种质资源的鉴定评价和遗传多样性研究、籽用南瓜产量、抗性、种皮颜色、 营养成分等重要农艺性状的遗传定位及调控研究等方面进行综述，同时，对籽用南瓜的研究方向进行展望，以期为籽用南瓜 种质创制和新品种选育提供一定的理论参考。