Target the core: durable plant resistance against filamentous plant pathogens through effector recognition

Plant pathogens colonize their host through the secretion of effector proteins that modulate plant metabolism and immune responses to their benefit. Plants evolve towards effector recognition, leading to host immunity. Typically, pathogen effectors are targets for recognition through plant receptors that are encoded by resistance genes. Resistance gene mediated crop immunity puts a tremendous pressure on pathogens to adapt and alter their effector repertoire to overcome recognition. We argue that the type of effector that is recognized by the host may have considerable implications on the durability of resistance against filamentous plant pathogens. Effector genes that are conserved among pathogens and reside in core genome regions are most likely to hold indispensable virulence functions. Consequently, the cost for the pathogen to overcome recognition by the host is higher than for diversified, host‐specific effectors with a quantitative impact on virulence. Consequently, resistance genes that directly target conserved effector proteins without the interception of other effector proteins are potentially excellent resistance resources. © 2019 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

马铃薯机械化收获除杂技术与装备研究进展

高效低损除杂是马铃薯机械化收获的核心环节,直接影响马铃薯的收获效率与收获品质,是助推马铃薯收获模式制定与收获装备研发与产业化进程的关键。由于不同马铃薯种植地区的自然环境等区域差异性较大,各地区马铃薯种植和收获模式复杂多变,因此对马铃薯机械化收获的除杂技术、装置结构和作业原理的需求各不相同。机械化收获除杂是减少生产成本、提高经济效益的重要方法,该研究基于国内马铃薯种植农艺,分析了国内外典型的马铃薯收获机基本结构和技术特点,对马铃薯机械化收获秧膜杂处理技术进行归纳总结,阐述薯土分离、薯秧分离、残膜回收及杂质清选等环节的装置结构与工作原理,对比分析不同除杂装置的特点与技术指标。针对国内覆膜种植、丘陵地区土壤粘重等特点,指出制约国内马铃薯除杂机械化发展的关键问题,并提出规范种植体系,研制适用机型与专用装备,农机农艺农信相融合和产学研相结合等建议,以期为马铃薯机械化收获除杂技术装备的研发应用奠定基础。     

神经干细胞的研究现状及展望

神经干细胞是一类具有自我复制、自我更新能力,高度增殖和多种分化潜能的神经前体细胞.为了进一步了解神经干细胞的特性,探求神经系统疾病治疗的新途径,文章参阅国内外相关文献,重点介绍了神经干细胞的分布、纯化培养的方法、增殖和分化的影响因素、应用及目前存在的问题等.     

马铃薯收获机扰动分离装置设计与试验

针对现有的小型马铃薯收获机筛面土块破碎效果不佳而影响分离效率和收获品质等问题,结合北方马铃薯主产区收获模式和常用杆条式分离装置,设计了一款马铃薯收获机扰动分离装置。在阐述总体结构及工作原理基础上,结合马铃薯的碰撞特性和土块的破碎过程分析,得到影响薯块损伤和土块破碎的主要因素为扰动深度、偏心轮转速和偏心距;通过EDEM-RecurDyn耦合构建仿真模型,单因素试验得到扰动杆数量最优为4,以扰动深度、偏心轮转速和偏心距为试验因素,以马铃薯碰撞力和土块破碎率为评价指标,运用Box-Behnken中心组合设计方法进行仿真试验,对试验结果进行方差分析,利用响应面分析了各交互因素对试验指标的影响规律,结合实际工况确定影响因素最佳取值。验证试验表明：当收获机分离筛运行速度为0.7m/s、扰动深度为51.5mm、偏心轮转速通过调速器设为2.3r/s、偏心距为31mm时,土块破碎率为60.7%,电子马铃薯采集的碰撞加速度峰值平均值为790.66m/s2,小于马铃薯临界损伤阈值。     

牛精原干细胞研究进展

精原干细胞(spermatogonial stem cells,SSCs)是雄性生殖系干细胞,位于睾丸曲细精管基膜上,既具有自我更新潜能,又具有定向分化潜能,是自然状态下出生后动物体内在整个生命过程中进行自我更新并能将基因传递至子代的惟一成体干细胞。根据国内外最新相关进展,系统评述了牛SSCs的生物学特性、分离纯化、冷冻保存、体外培养、永生细胞系的建立及移植等方面的现状及问题。     

叶尔羌高原鳅外周血淋巴细胞的分离

以体质健康的叶尔羌高原鳅为研究对象,分离其外周血淋巴细胞。结果表明,采用浓度为1.085g/mL的淋巴细胞分离液在2000r/min离心35min的情况下,可将叶尔羌高原鳅外周血淋巴细胞有效地分离出来。该研究不仅为叶尔羌高原鳅淋巴细胞功能研究提供了依据,还可为叶尔羌高原鳅的疾病防治、人工养殖提供重要参考。     

植物品种权交易定价策略的博弈分析

文章基于不完全信息动态博弈中精炼贝叶斯均衡的准分离均衡对植物品种权交易定价策略进行分析,得出交易双方在各自不同情况下的最优选择。分析认为,对于一次独立的交易,植物品种权转让方在其提供的品种权具有高开发价值的情况下,只会选择定高价,而在其提供的品种权具有低开发价值的情况下,会利用信息不对称特性,根据受让方对高定价选择购买的概率大小决定选择定高价或低价,双方博弈的重点就在于转让方对于受让方在其定高价时会选择买的概率的估计;对于连续不断交易,最终却只会存在高开发价值定高价和低开发价值定低价的两种博弈结果。最后,提出实现这种长期博弈均衡结果的对策建议。     

Tobacco cultivars vary in induction of systemic resistance against <Emphasis Type="Italic">Cucumber mosaic virus</Emphasis> and growth promotion by <Emphasis Type="Italic">Pseudomonas chlororaphis</Emphasis> O6 and its <Emphasis Type="Italic">gacS</Emphasis> mutant

The colonization of plant roots with certain rhizosphere bacteria promotes plant growth and induces long lasting systemic protection against a broad spectrum of plant pathogens. The role of the global regulator, GacS, in the rhizosphere colonist Pseudomonas chlororaphis O6 in stimulating growth promotion and induced resistance against Cucumber mosaic virus was examined in tobacco. Responses were compared in tobacco cvs Samsun and GX3. Root colonization of Samsun with wild-type O6 and the gacS complemented mutant-elicited reduced viral symptoms and viral titre. On GX3, there was little affect on symptoms when roots were colonized by the wild-type, gacS mutant or complemented mutant but colonization by both the wild-type and the gacS mutant lowered viral titre. Wild-type O6 and the gacS mutant caused plant growth to be maintained in both tobacco cultivars after viral infection, although the affect was stronger with GX3 than Samsun. In contrast, although a chemical inducer, benzothiadiazole, reduced symptoms and viral titre in both cultivars, plant growth was suppressed. Our results indicate rhizobacteria-elicited induced viral resistance without a negative impact on growth but there was a differential response between cultivars. Detailed knowledge regarding the mechanisms inherent to these differences between cultivars requires further investigation.     

中国东北苹果园中土壤总硝化作用和氧化亚氮排放状况

A better understanding of nitrogen (N) transformation in agricultural soils is crucial for the development of sustainable and environmental-friendly N fertilizer management and the proposal of effective N₂O mitigation strategies. This study aimed: i) to elucidate the seasonal dynamic of gross nitrification rate and N2O emission, ii) to determine the influence of soil conditions on the gross nitrification, and iii) to confirm the relationship between gross nitrification and N₂O emissions in the soil of an apple orchard in Yantai, Northeast China. The gross nitrification rates and N₂O fluxes were examined from March to October in 2009, 2010, and 2011 using the barometric process separation (BaPS) technique and the static chamber method. During the wet seasons gross nitrification rates were 1.64 times higher than those under dry season conditions. Multiple regression analysis revealed that gross nitrification rates were significantly correlated with soil temperature and soil water-filled pore space (WFPS). The relationship between gross nitrification rates and soil WFPS followed an optimum curve peaking at 60% WFPS. Nitrous oxide fluxes varied widely from March to October and were stimulated by N fertilizer application. Statistically significant positive correlations were found between gross nitrification rates and soil N₂O emissions. Further evaluation indicated that gross nitrification contributed significantly to N₂O formation during the dry season (about 86%) but to a lesser degree during the wet season (about 51%). Therefore, gross nitrification is a key process for the formation of N₂O in soils of apple orchard ecosystems of the geographical region.     

中国大陆“诽官案”实证研究

1996年至2010年在大陆报刊、杂志、网络上可检索到的“诽官案”共计45件。这些被舆论称为“官告民”的刑事诽谤案激起了人们的广泛关注与争鸣,甚至成为了舆情、政情的风向标。用实证研究的方法来解读这些现实案例所呈现出的诸多问题,可观我国社情、舆情以及官民关系之一斑,并站在“让公权力在阳光下运行”的视角,为中国当下“诽官案”现象提供政治与法律上的应对之策。