二十四节气话农事

古有谚语:"春雨惊春清谷天,夏满芒夏暑相连,秋处露秋寒霜降,冬雪雪冬小大寒"来描绘中国的立春、雨水、惊蛰、春分、清明、谷雨、立夏、小满、芒种、夏至、小暑、大暑、立秋、处暑、白露、秋分、寒露、霜降、立冬、小雪、大雪、冬至、小寒、大寒二十四节气,可见节气变化对于农业生产的重要性。在人类从事农业生产的早期,由于播种收获等农事活动,已经认识到春生夏长秋收冬藏的规律。中国秦汉便有了完整的二十四节气,用以指导农业生产;东汉《四民月令》记述按月和节气安排农事活动;北魏《齐民要术》阐明以节气为依据安排耕、种、收。后世各代也都以二十四节气决定农时的依据。我们借鉴前人的经验,凭借科学的态度,应读者的要求特别开辟《二十四节气话农事》专题,对于广大农民朋友正确运用二十四节气,掌握天气气候规律,科学安排日常生产生活,顺应农时、不违农时,破除迷信、科学种田,争取农业丰收,都有着重要的参考作用。     

巴西农药市场特点

巴西是南美洲最大的国家,国土面积为851.49万平方公里,约占南美洲总面积的46%,居世界第五,仅次于俄罗斯、加拿大、美国与中国。巴西是农业大国,主要农作物有大豆、甘蔗、玉米、稻米、咖啡、子棉、木薯、柑桔、烟叶、芸豆、香蕉、小麦、马铃薯、西红柿、葡萄等。其中,巴西是世界第一大咖啡生产国和出口国、最大的蔗糖生产和出口国、第二大大豆生产和出口国、第三大玉米生产国。全国可耕地面积约4亿公顷,被誉为"二十一世纪的世界粮仓"。巴西于2008年代替美国成为全球最大的农药市场,2011年在甘蔗、棉花、咖啡、小麦、大豆和玉米等作物需求量的驱动下,农药销售额达到新高。根据巴西国家农药工业联     

茶入联中香隽永

茶之为饮,发乎神农氏,闻于鲁周公。中国是世界上较早发现和利用茶叶的国家之一,人们在长期的饮茶过程中,给茶渗入了丰富的文化内涵,逐渐形成了独特的文化现象。茶与文化关系至深,涉及民俗、宗教、文学、美术、书法、诗词、楹联、旅游、戏曲、音乐、歌舞等诸多领域。楹联是我国特有的文化艺术形式,种类繁多,茶联便是其中之一。楹联始于五代,亦称楹贴、对联,是悬挂或粘贴在柱身、门上的联语,由一联对偶句组成,以讲究工整的对仗,有“字数相等、词性相同、结构相应、句式相似、内容相关、平仄相对”的要求。     

襄州区植保专业化统防统治工作现状与对策

近几年来,襄州区植保站贯彻＂预防为主,综合防治＂的植保方针和＂公共植保、绿色植保＂的植保理念,按照＂政府支持、市场运作、农民自愿、绿色植保＂的原则,以提高防效、降低成本、减少用药、保障生产为目标,以集约项目、整合力量、优化技术、创新服务、规范管理为突破口,     

草履蚧的发生与综合防治

草履蚧(Drosicha corpulenta)又名草鞋虫,树虱子,属同翅目绵蚧科。我国东北、华北、华中、华东等地均有发生,以若虫和雌成虫为害树木。主要为害杨树、柳树、槐树、胡桃、白蜡、杏树、柿树、桃树、梨树、苹果树、樱桃树等树木的枝、干、芽,     

农家小顾问——二十四节气话农事（续）

古有谚语：＂春雨惊春清谷天,夏满芒夏暑相连,秋处露秋寒霜降,冬雪雪冬小大寒＂来描绘中国的立春、雨水、惊蛰、春分、清明、谷雨、立夏、小满、芒种、夏至、小暑、大暑、立秋、处暑、白露、秋分、寒露、霜降、立冬、小雪、大雪、冬至、小寒、大寒二十四节气,可见节气变化对于农业生产的重要性。在人类从事农业生产的早期,由于播种收获等农事活动,已经认识到春生夏长秋收冬藏的规律。中国秦汉便有了完整的二十四节气,用以指导农业生产。我们借鉴前人的经验,凭借科学的态度,应农民朋友的要求特别开辟《二十四节气话农事》专题,对于广大农民朋友正确运用二十四节气,掌握天气气候规律,科学安排日常生产生活,顺应农时、不违农时,破除迷信、科学种田,争取农业丰收,都有着重要的参考作用。     

西北地区秋季干旱指数的变化特征

利用甘肃、宁夏、青海、新疆4省(区)的137个气象站30年的降水、蒸发资料,确定适合西北地区的干旱指数计算方法,分析中国西北地区秋季降水、蒸发、干旱指数的空间分布、时间演变等特征.结果表明:西北地区秋季平均自然降水从东南到西北依次减少,在甘肃西部、青海西北部、新疆南部有一条东西向的少雨带,是干旱最严重的地方.新疆南部、甘肃西部、青海西部重旱频率最高,平均2年一遇;新疆北部、甘肃南部、青海南部、中旱频率为30%左右,平均3年一遇,轻旱频率30%左右,平均3年一遇.表明西北地区的干旱有明显的地域特征,即新疆中南部、甘肃西部、青海西部为干旱区,新疆北部、甘肃中东部、青海东部和南部为半干旱区.     

甘肃省榆中县菜地土壤与蔬菜中重金属含量及健康风险评估

在甘肃省榆中县蔬菜基地,选择30个点位采集4种蔬菜(120株) 及相应的土样,在分别对重金属Hg、Cd、Pb、Cr、Cu 含量分析测试的基础上,开展蔬菜重金属污染评价、富集能力分析及健康风险评估。结果表明：研究区土壤中Hg、Cd、Pb、Cr、Cu平均含量分别为0.159、0.364、15.001、37.633、31.298 mg·kg^-1,土壤中Pb、Cr含量均低于兰州市土壤背景值,但Hg、Cd、Cu含量均超过了兰州市土壤背景值。蔬菜中Hg、Cd、Pb、Cr、Cu平均含量分别为0.0037、0.0115、0.0293、0.0226、0.1874 mg·kg^-1鲜重,均低于食品中污染物限量标准,它们的单项污染指数分别为0.37、0.06、0.10、0.05、0.02,综合污染指数为0.60,研究区蔬菜重金属污染属于安全级。蔬菜中Hg、Cd、Pb、Cr、Cu平均富集系数分别为0.023、0.033、0.002、0.001、0.006,重金属富集系数的大小顺序为Cd＞Hg＞Cu＞Pb＞Cr,Cd在蔬菜中的富集能力最强。成年人食用研究区蔬菜摄入的Hg、Cd、Pb、Cr、Cu平均值分别为1.11、3.45、8.79、6.78、56.22 μg·人^-1·d^-1,分别只占ADI值的2.58%、5.75%、4.11%、3.39%、0.47%。当地居民通过食用蔬菜产生的重金属Hg、Cd、Pb、Cr、Cu健康风险系数分别为0.03、0.06、0.04、0.04、0.01,总健康风险系数为0.17,因此人群长期食用研究区蔬菜所产生的重金属健康风险极低。     

农业生产安全形势分析与探索

房县耕地面积3.2万hm2,是典型的山区农业大县.主要农作物有水稻、玉米、小麦、柑橘、中药材、烟草、高山蔬菜等.通过耕作制度改革,实施良种工程,温饱工程、国家粮食科技丰产工程、沃土工程、植保工程等农业项目,实现了面积缩小,单产提高,总产增加,效益提高,人均占粮食稳步上升的目标.但随着国民经济的快速发展和多种复杂因素的影响,农业生产形势趋于严重,威胁农业生产安全方面趋于多面化、复杂化.     

乙酰甲胺磷的生产与应用

乙酰甲胺磷是一种有机磷类杀虫剂,具有低毒、广谱、内吸性强、持效期长等特点,被广泛应用于水稻、棉花、蔬菜、果树、小麦、甘蔗等作物防治稻纵卷叶螟、稻飞虱、二化螟、三化螟、叶蝉、蚜虫、菜青虫、叶螨等害虫。近年来,随着甲胺磷等高毒农药被禁止使用,乙酰甲胺磷的应用越来越受到重视,已经成为成长最快的高毒农药替代品种之一（以下简称“替代品种”）,目前无论是在原药生产工艺的技术创新上、新制剂品种的开发上,还是应用技术的研究推广上,乙酰甲胺磷都步入了发展的快车道。     

Interactions between citrus viroids affect symptom expression and field performance of clementine trees grafted on trifoliate orange

ABSTRACT Citrus exocortis viroid (CEVd), Citrus bent leaf viroid (CBLVd), a noncachexia variant of Hop stunt viroid (HSVd), Citrus viroid III (CVd-III), and Citrus viroid IV (CVd-IV) were co-inoculated as two-, three-, four-, and five-viroid mixtures to Clementine trees grafted on trifoliate orange to evaluate their effect on symptom expression, tree growth, and fruit yield. Most trees infected with CEVd-containing viroid mixtures developed exocortis scaling symptoms, as did CEVd alone, whereas most trees infected with HSVd- or CVd-IV-containing mixtures developed bark-cracking symptoms. Trees infected with mixtures containing both CEVd and CVd-IV revealed the existence of antagonism between these two viroids in terms of the expected bark-scaling and cracking symptoms. Synergistic interactions also were identified in trees infected with certain viroid combinations that, in spite of lacking CEVd, expressed exocortis-like scaling symptoms. Viroid interactions also affected the expected response of trees in terms of vegetative growth and fruit yield. Trees infected with viroid combinations containing CEVd or CVd-III were smaller and produced less fruit than trees infected with mixtures not containing these viroids. Viroid interactions on scion circumference and cumulative fruit yield, in terms of additivity of their effects, were statistically confirmed using a factorial analysis of variance model with two mean estimation approaches. In single-viroid infections, CEVd, CVd-III, and, to a lesser extent, CBLVd consistently and significantly reduced tree size and fruit yield. Conversely, HSVd and CVd-IV slightly increased fruit yield and reduced scion circumference. Rare and not consistent significant interactions were detected with the five-, four-, and three-viroid combinations. Antagonistic interactions between CEVd and CVd-III or CBLVd and CVd-III were revealed over the years with consistent significance. The antagonistic interaction between CEVd and CVd-IV was highly significant over the years when additional viroids were present; however, this antagonism appeared much later in the case of an exclusive interaction. HSVd and CVd-IV showed a consistent and significant synergistic interaction on yield only when both viroids were exclusively present. These results demonstrate antagonistic or synergistic relationships between citrus viroids depending on the viroid mixtures present in the host.     

Separation of citrus viroids by shoot-tip grafting in vitro

Arizona 861-S1 citron ( Citrus media L.) infected with a severe exocortis isolate containing four citrus viroids was used as source of tissue for shoot-tip grafting in vitro. Out of 51 attempts, 25 successful grafts were obtained. Only 16 plants survived transplanting and of these 12 were viroid-free. The viroid profile of the other four plants showed fewer viroids than the original field source. The significance of these results, as compared with previous reports on the recovery of viroid-free plants, is discussed. The results show the usefulness of shoot-tip grafting in vitro as a tool to recover single viroid isolates from complex field sources.     

<Emphasis Type="Italic">Citrus exocortis viroid</Emphasis> transmission through commercially-distributed seeds of <Emphasis Type="Italic">Impatiens</Emphasis> and <Emphasis Type="Italic">Verbena</Emphasis> plants

Surveys of Impatiens and Verbena species in local nurseries in Fredericton, Canada and Verbena species in New Delhi, India showed widespread infection of Citrus exocortis viroid (CEVd) in vegetatively-propagated and seed-grown plants. To determine viroid seed transmission, samples of eight varieties of Impatiens and 11 varieties of Verbena were obtained from four commercial sources. All 19 samples collected contained viroid infection irrespective of variety. The presence of viroid in non-germinated seed was 21%, while the transmission rate in seedlings was 66% in Impatiens walleriana in 2006. Following 2 years of seed storage, the respective figures were 6% and 26%. Similarly, in Verbena x hybrida the presence of viroid in seed was 13% in 2006 with a seed-transmission rate in seedlings of 28%, while the respective figures after 2 years of storage were 5% and 45%.     

Host Effect on the Molecular and Biological Properties of a Citrus exocortis viroid Isolate from Vicia faba

ABSTRACT Citrus exocortis viroid (CEVd) is the casual agent of citrus exocortis disease, and has been found in naturally infected citrus and noncitrus hosts. Field isolates of CEVd may infect susceptible hosts as a complex of genetically related sequence variants (haplotypes). In the present work, a CEVd isolate recovered from a symptomless broad bean plant was characterized as a heterogeneous population with a nucleotide diversity of 0.026, which did not contain a predominant haplotype. When nucleic acid extracts of this infected broad bean were used to inoculate tomato, the plants displayed symptoms and the CEVd population was more homogeneous, with a nucleotide diversity of 0.007. However, when nucleic acid extracts from this tomato isolate were back inoculated to new broad bean plants, this isolate did not revert to the original population, because it showed low nucleotide diversity (0.001) and induced symptoms in the broad bean plants. Symptomless broad bean plants may act as reservoirs of highly heterogeneous populations of CEVd variants, providing an excellent inoculum source in terms of its potential to infect a broad range of putative hosts. The epidemiological implications are discussed.     

Effects of resistance of Eremocitrus glauca and Microcitrus australis to viroid infection: replication,accumulation and long‐distance movement of six citrus viroids

In studies to identify genotypes resistant to infection with citrus viroids, Eremocitrus glauca and Microcitrus australis were selected because their evolution in their habitat in Australia and New Guinea may have led to the selection of unusual traits. The movement and accumulation of Citrus exocortis viroid (CEVd), Hop stunt viroid, Citrus bent leaf viroid, Citrus dwarfing viroid, Citrus bark cracking viroid and Citrus viroid V (CVd‐V) in self‐rooted as well as in graft‐ propagated E. glauca and M. australis plants was assessed by northern hybridization, RT‐PCR and by topworking to the sensitive selection 861‐S1 of Etrog citron. In both plant species the inoculated viroids were undetectable unless these plants were grafted to a susceptible Citrus partner, the rough lemon rootstock and/or the topworked Etrog citron, which acted as viroid sources. The results obtained indicate that M. australis and in particular E. glauca are poor viroid hosts in which viroid replication/accumulation does not occur or is extremely inefficient. However, viroid downward and upward movement to grafted Citrus partners in which viroid replication and accumulation occurs efficiently was not impaired. Eremocitrus glauca and M. australis showed differences regarding their properties as viroid hosts, but for both species CEVd seemed to have the lowest affinity among the viroid species tested and CVd‐V the highest. Even though E. glauca and M. australis do not appear to be truly resistant to viroid infection, they are interesting genotypes for further characterization of the mechanisms involved in viroid infection.     

Incidence in Cyprus of citrus exocortis viroid and its mechanical transmission

A survey for citrus exocortis viroid (CEV) was conducted in commercial groves of the main citrus-producing areas of Cyprus during 1987–1990. Of 573 trees sampled, representing 25 species and varieties, 506 (88.3%) were found to be infected when indexed by grafting to seedlings of'Etrog' citron (Citrus medica) , selection Arizona 861. Levels of infection by CEV were lower in newer introductions than in introductions made before the 1940s. In greenhouse tests, CEV was readily transmitted from citron to healthy citron and gynura (Gynura aurantiaca) by knife-blade inoculation. Retransmission of CEV from infected gynura back to citron was successful.