牦牛KDM2A基因克隆及其在不同组织和减数分裂进程的表达

组蛋白去甲基化酶(histone demethylase,KDM)2A是细胞周期基因表达所必需的调控分子。为了研究牦牛(Bos grunniens)KDM2A基因的结构和功能,并进一步分析该基因在不同组织及卵母细胞减数分裂进程中的表达模式,本研究首先克隆获得牦牛KDM2A基因序列全长3 546 bp,包括完整的开放阅读框3 489 bp,编码氨基酸1 162个(Gen Bank登录号:MH345760)。牦牛KDM2A基因与其他物种的相似度与构建的系统进化树结果一致。牦牛KDM2A蛋白分析显示,其理论分子质量为132.7 k D,理论等电点为7.59,不稳定指数52.73,总平均亲水指数-0.587。KDM2A蛋白氨基酸序列中存在117个磷酸化位点,6个N-糖基化和2个O-糖基化位点;二级结构包括无规则卷曲、α螺旋和β折叠。KDM2A蛋白含有cupin超家族jumonji-C(Jmj C)结构域、锌指(CXXC zinc finger,ZF-CXXC)结构域、植物同源域(plant homeodomain,PHD)、F-盒蛋白(F-box,FBOX)结构域和有丝分裂相关蛋白(antagonist of mitotic exit network protein 1,AMN1)结构域,不含跨膜结构域和信号肽,主要在细胞核发挥生物学功能。KDM2A mRNA在子宫、脾脏和卵巢的表达量较高,极显著高于其他组织(P0.01);KDM2A mRNA在卵母细胞减数分裂过程中均表达,其中MⅡ期的表达量极显著高于GⅤ期和MⅠ期(P0.01),GⅤ期KDM2A的表达水平高于MⅠ期,但差异不显著(P0.05)。本研究成功克隆了牦牛KDM2A基因序列,并明确其在组织和卵母细胞减数分裂进程中的表达模式,为深入探讨KDM2A基因在牦牛卵母细胞减数分裂进程中的作用机制提供了基础资料。     

半滑舌鳎甲状腺激素受体β基因(TRβ)的克隆与表达分析

甲状腺激素在鲽形目仔鱼的变态过程中起着重要的作用,而甲状腺激素的生物效应是由甲状腺激素受体(thyroid hormone receptors,TRs)介导的。本研究利用RACE技术克隆了半滑舌鳎(Cynoglossus semilaevis)TRβ基因的全长,并对其功能进行了生物信息学分析。结果显示,TRβ基因(GenBank登录号:No.KJ499433)cDNA全长为2 345 bp,开放读框(open reading frame,ORF)长1 188 bp,编码396个氨基酸,5'-UTR和3'-UTR分别长454和703 bp。通过氨基酸序列比对发现,TRβ氨基酸序列铰链区有一段由9个氨基酸残基组成的插入序列,推测这段序列可能为硬骨鱼类TRβ基因所特有的。实时荧光定量PCR技术分析结果显示,TRβ基因在各组织中均有表达,且在肝组织中的表达量显著高于其他组织(P0.05);因此推测TRβ基因在半滑舌鳎成鱼各组织中具有多样性的功能,而且其在肝脏的新陈代谢中起到重要的调节作用。在半滑舌鳎仔鱼变态时,TRβ基因的表达量随变态开始而迅速增加,在变态高峰期到达最高。药物处理实验结果显示,正常变态和提前变态的仔鱼TRβ基因的表达水平均随变态开始而迅速上调,而变态被抑制的仔鱼中TRβ基因的表达量则未出现显著变化,表明TRβ是调控半滑舌鳎仔鱼变态过程的重要基因,在半滑舌鳎生长发育早期阶段起较关键作用。本研究为深入解析半滑舌鳎变态的分子机制提供了理论依据和参考。     

半滑舌鳎转化生长因子TGF-β1和TGF-β3基因的克隆及受哈维氏弧菌感染后表达分析

转化生长因子β (transforming growth factor β,TGF-β)是一类具有多种功能的蛋白超家族,在细胞免疫、细胞增殖分化和组织损伤的修复中起着关键性作用.本研究从半滑舌鳎(Cynoglossus semilaevis)肝脏中克隆获得了TGF-β1和TGF-β3基因.推导的TGF-β1和TGF-β3氨基酸序列均含有多个N糖基化位点和一个TGF-β家族标签.系统进化树分析显示,半滑舌鳎TG F-β1和TGF-β3分别与鱼类的TGF-β1和TGF-β3亲缘关系最为密切.qRT-PCR结果表明,半滑舌鳎TGF-β1和TGF-β3基因在健康鱼的多个组织中均有表达,二者在皮肤中表达量最高,在肌肉中表达量最低.经哈维氏弧菌(Vibrio harveyi)感染后,TGF-β1在肝脏、脾脏和肾脏中呈现先上升后下降的表达趋势,在感染48 h后的肝脏中表达量达到最大值,是对照组的3.17倍;TGF-β3在脾脏、肾脏和鳃中也呈现先上升后下降的表达趋势,在感染24 h后的鳃中表达量达到最大值,是对照组的4.71倍.以上结果提示,TG F-β1和TGF-β3可能在半滑舌鳎抵御细菌感染的免疫中发挥了重要作用,本研究为证明二者参与机体免疫调节提供了有力证据,为半滑舌鳎分子免疫研究提供了理论依据.     

绵羊PGRMC1蛋白的cDNA克隆、序列分析及组织表达

孕激素受体膜组分1 (progesterone receptor membrane component 1,PGRMC1)是膜相关孕激素受体蛋白家族成员之一,参与哺乳动物颗粒细胞和黄体细胞孕酮的抗凋亡过程,在促进卵母细胞成熟和维持卵巢机能方面具有重要作用.本研究通过RT-PCR对绵羊(Ovisaires)PGRMC1基因进行了克隆和组织表达谱分析,并利用实时荧光定量PCR对该基因在繁殖特性上存在明显差异的两个绵羊品种——多浪羊(常年发情)与中国美利奴羊(季节性繁殖)发情期和乏情期性腺轴组织的表达情况进行了检测.结果获得了绵羊PGRMC1基因部分cDNA序列(GenBank登录号:KM114208),其中编码区(Coding sequence,CDS)全长585 bp,编码194个氨基酸.其编码蛋白中包含一个Cyt-b5保守结构域.该基因在所检测绵羊各组织中广泛表达,其中以卵巢、子宫、肝脏、肾脏和下丘脑组织表达丰度较高.实时荧光定量PCR结果显示,同一绵羊品种发情期子宫、卵巢和松果体PGRMC1 mRNA水平均高于乏情期;不同绵羊品种间性腺轴组织基因表达水平存在一定差异,无论是发情期还是乏情期,多浪羊子宫、卵巢和松果体中PGRMC1 mRNA水平均高于同期的中国美利奴羊.本研究结果表明,PGRM C1在维持绵羊子宫与卵巢机能、调节激素分泌和发情行为等方面可能发挥重要作用.为进一步了解PGRMC1的生物学功能提供一定的理论依据.     

拟南芥泛素家族的全基因组分析

泛素家族是一类含有保守性泛素结构域的蛋白质统称,主要通过ATP依赖性的泛素-蛋白水解酶复合体通路选择性降解细胞蛋白的各种生理活动。本研究基于HMM模型,已知泛素氨基酸序列作为训练集,搜索拟南芥信息资源数据库并鉴定AtUBQ家族成员,然后对这些基因编码的蛋白质序列进行基因结构分析、染色体定位、多序列联配、系统发育树构建和组织差异表达分析。结果表明,AtUBQ家族中共有13个推定的AtUBQ基因,命名为AtUBQ01~AtUBQ13,均属无内含子基因且结构基本相同,非均匀分布于拟南芥5条染色体;AtUBQ家族可划分为A、B和C3个亚家族,其中76.92%的基因编码蛋白质属于A亚家族;EST搜索发现除AtUBQ02和AtUBQ07基因无EST数据支持外,余下的AtUBQ基因在拟南芥根、芽和叶等7个组织中呈现差异表达,仅见AtUBQ08和AtUBQ10基因在上述7个组织中均表达,而AtUBQ03基因仅表达于叶中。本研究结果可为进一步开展该家族的生物学功能和分子进化机制的研究提供基础资料。     

一种快速鉴定半滑舌鳎遗传性别的方法

半滑舌鳎(Cynoglossus semiliaevis)遗传性别快速准确鉴定的方法是性别控制与高雌苗种培育的基础,其性别决定机制为ZW型,遗传雌鱼为异型染色体ZW,遗传雄鱼为同型染色体ZZ.本研究在半滑舌鳎全基因组测序结果的基础上,通过分析Z染色体和W染色体差异序列,设计一对跨Z/W染色体同源差异DNA片段的引物CS-SEX-F和CS-SEX-R,取半滑舌鳎部分鳍条通过碱煮沸方法获得的DNA为模板,采用PCR扩增,琼脂糖凝胶电泳方法鉴定半滑舌鳎遗传性别.通过该方法在遗传雄鱼(ZZ)个体中可以扩增出366 bp的DNA条带,遗传雌鱼(ZW)个体中可以扩增出366和253 bp两种DNA条带.本研究建立了一种新的成本低廉、操作快速、结果准确可靠的鉴定半滑舌鳎遗传性别的方法,该方法与已有方法相比,操作简便省时,为半滑舌鳎遗传学研究与性别控制育种相关研究提供了可靠分子标记,在半滑舌鳎遗传性别鉴定和养殖场所内伪雄鱼快速检测方面具有广阔的应用前景.     

甘蔗锌指蛋白基因的克隆和表达分析

在对甘蔗(Saccharum officinarum)叶片全长cDNA文库测序的基础上,获得1个编码锌指蛋白基因的全长cDNA序列,命名为Sc-zf.生物信息学分析表明,该基因全长1 189 bp,编码171个氨基酸,具有zf-A20和zf-AN1两个锌指结构域;构建了包含Sc-zf开放读码框的原核表达载体,经IPTG诱导,目的基因原核表达产物大小约为18.3 kD;经定量PCR技术分析,该基因在黑穗病菌(Ustilago scitaminea)、水杨酸(SA)、H2O2、NaCl和PEG胁迫下表达特性不同,受到黑穗病菌和NaCl的诱导,PEG的抑制,但也受SA和H2O2的影响.     

鲤CC型趋化因子CCL-C5a样基因的克隆、组织表达与进化分析

趋化因子家族是一类能诱导白细胞激活和迁移的趋化性细胞因子家族,是鱼类先天免疫的重要组成部分.CC类家族是趋化因子家族中最大的家族之一.为研究鲤CC类家族成员的组织表达和进化模式,以及进一步研究鲤CC类趋化因子的免疫调控机制,本研究选择该家族其中的一个基因,CCL-C5a样基因,根据EST序列结合RACE方法从鲤(Cyprinus carpio)脾脏中克降了该基因的全长cDNA序列(GenBank登录号:JQ026408).该序列全长830 bp,5端非翻译区174 bp,3端非翻译区296 bp,开放阅读框360 bp,编码一个由119个氨基酸组成的蛋白.结构域分析发现,该蛋白质含有分泌信弓肽和保守的趋化因子结构域;Gene Ontology注释该基因参与免疫细胞迁移的生物学过程.CCL-C5a基因在鲤10个组织中表达,其中在脾和肝的表达量最高.脂多糖刺激鲤外周血白细胞和头肾白细胞后,该基因表达量出现显著上升.氨基酸序列保守性分析表明,鲤CCL-C5a样趋化因子与斑马鱼(Danio rerio)的同源性最高,为61％,与蓝鲶(Ictalurus futrcatus)、沟鲶(Ictalurusp unctatus)和大西洋鲑(Salmo salar)的同源性分别为47％、47％和42％;与人(Homo sapiens)CCL19蛋白的同源性为37％.适应性进化分析发现,鲤与斑马鱼CCL-C5a的Ka/Ks小于1,说明CCL-C5a基因在鱼类的进化过程受到负选择压作用.本研究结果表明,鲤CCL-C5a主要在免疫器官上高表达,并受到脂多糖诱导表达上升;同时该基因在鱼类中受到负选择作用.这些结果提示CCL-C5a可能是一个与免疫相关的基因.     

植物非生物逆境相关锌指蛋白基因的研究进展

植物能够适应多种逆境主要是通过改变其基因表达和代谢途径来实现的,因此研究这些基因表达和功能对提高植物耐逆性具有重要意义。锌指蛋白是一类具有手指状结构域的转录因子,这种结构域由锌离子与多个半胱氨酸和(或)组氨酸组成,锌离子在稳定其结构和发挥调控功能方面具有关键作用。植物锌指蛋白在植物耐逆性方面具有重要作用。本文综述了近几年来从拟南芥(Arabidopsis thaliana)、水稻(Oryza sativa)、小麦(Triticum aestivum)、番茄(Solanum lycopersicum)等植物中克隆的与非生物逆境相关锌指蛋白基因的研究成果,重点阐述了其基因表达部位、受逆境诱导情况及转基因植株的耐逆性等。目前的研究结果表明锌指蛋白能够调控耐逆相关基因的表达,在植物逆境代谢中发挥重要作用,因此可以利用锌指蛋白基因进行作物耐逆性的遗传改良,提高作物的耐逆能力。     

非生物胁迫诱导的玉米蛋白激酶基因ZmCIPK1的cDNA克隆和表达分析

CIPK（CBL-interacting Protein Kinase）在植物非生物胁迫信号转导中起重要作用。应用电子克隆的方法在玉米中克隆了一个cDNA全长为1395bp的蛋白激酶基因ZmCIPK1（GenBank接受号为EF158034）。其编码的蛋白含有465个氨基酸,分子量为51.98KD,等电点为6.92。推断的ZmCIPK1催化结构域中包含蛋白激酶催化结构域保守的11个亚结构域, 蛋白C端具有植物CIPK蛋白家族特有的包含24个氨基酸的NAF结构域。半定量RT-PCR结果表明,在甘露醇、氯化钠、ABA和4°C低温诱导时,ZmCIPK1在玉米幼苗叶片中表达量明显上调,在24小时内保持较高的转录水平。试验结果表明,ZmCIPK1是一个新的玉米蛋白激酶基因,响应多种非生物胁迫信号。     

低氮和干旱胁迫对富士和秦冠生长及氮素利用的影响

【目的】以富士（Fuji）、 秦冠（Qinguan）嫁接在平邑甜茶（Malus hupehensis Rehd.）上的当年生盆栽苗为试验材料,采用砂培方法,研究了缺氮胁迫和干旱对富士和秦冠生长情况、 光合参数、 植株各部位氮磷钾含量及氮素利用效率的影响,分析比较了低氮干旱条件下富士和秦冠生长及氮素利用的差异,以期为果树生产高效肥水利用提供理论指导。【方法】试验共设四个处理: 正常氮正常水（ZZ）、 低氮正常水（DZ）、 正常氮干旱（ZG）、 低氮干旱（DG）。氮素和水分均设置两个水平,分别为正常氮（6 mmol/L NO-3-N）、 低氮（0.3 mmol/LNO-3-N）、 正常供水（保持盆中砂子相对含水量为饱和含水量的80%~85%）、 干旱处理（保持盆中砂子相对含水量为饱和含水量的60%~65%）。【结果】富士和秦冠的生物量（茎和叶）、 株高茎粗等生长指标以及光合速率、 气孔导度、 蒸腾速率均为正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）,并且相对应处理下秦冠的以上指标均高于富士;正常供水下,缺氮处理使富士、 秦冠的根冠比比正常氮处理均有所增加,富士提高了2.05%,秦冠提高了22.40%。富士和秦冠的氮、 磷、 钾含量均表现出正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）; 氮、 钾元素含量在植株各部位的分布顺序依次是叶＞根＞茎,磷元素则是根＞叶＞茎;光合氮素利用效率（PNUE）和氮素利用效率表现为秦冠处理之间差异极显著,富士处理之间差异不显著;秦冠的PNUE和NUE明显高于富士,在低氮正常水（DZ）处理下,秦冠氮肥利用率比富士高42.07%,在低氮干旱（DG）处理下高64.14%;低氮胁迫下富士和秦冠的NUE显著提高,并且秦冠提高的幅度高于富士。【结论】施用氮肥能够显著提高富士与秦冠的干物质量,同等水肥条件下,秦冠生长优于富士;水分亏缺会减少叶片对氮的吸收,干旱条件下适度增施氮肥,可提高果树的抗旱能力;低氮干旱胁迫下秦冠的生长指标、 光合指标及氮素利用效率指标均优于富士,表现出较强的抗低氮干旱胁迫的能力。     

Pasture Vegetation Elemental Analysis by Laser-Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is a new technique for the analysis of plant material. This study investigates the application of LIBS to pasture-based plant samples. The LIBS measurements were obtained from pelletized pasture samples (100 samples) that had been also analyzed by inductively coupled plasma–optical emission spectroscopy (ICP-OES) following microwave digestion for calibration and comparison purposes. Comparisons for elements sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), boron (B), phosphorus (P), and sulfur (S) showed that LIBS could be used for almost all the standard profile total elements with concentrations down to low mg/kg levels (observed error of Na: 0.024 percent, K: 0.18 percent, Mg: 0.016 percent, Ca: 0.073 percent, P: 0.017 percent, Mn: 31 mg/kg, Fe: 150 mg/kg, Zn: 6.6 mg/kg, and B: 1.1 mg/kg). Elemental analysis at less than mg/kg levels was not possible using LIBS. The elements S and Cu were particularly difficult to analyze with reliability using LIBS at the concentration levels found in the plant samples. Replacing microwave digestion and subsequent ICP analysis with a direct analysis of dried plant samples using LIBS has the potential to improve the productivity and reduce the cost of testing.     

Faculty positions:Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Assessing the effectiveness of conservation measures: Resolving the “wicked” problem of the Steller sea lion

“Wicked” problems are those that are complex and that change when solutions are applied. Many conflicts in conservation fall into this category. The study approached the problem of how to constrain the apparent wickedness of a problem in the conservation management of a species by using simple empirical indicators to carry out iterative assessment of the risk to a population and to document how this risk evolves in relation to the addition of new data and the implementation of management actions. Effects of high levels of uncertainty within data and also concerning population structure were examined through stochastic simulation and by exploration of scenarios. Historical trends in the example used, the Steller sea lion, showed rapid declines in abundance in some regions during the 1980s. The current total population is 130,000-150,000 Steller sea lions through Alaska and British Columbia and this number has been stable since about 1990 in spite of regional differences in population dynamics. Regional differences in the sequence of changes in the number of pups and non-pups, suggested that an internal re-distribution of juveniles could have happened between 1980 and 1990. Current productivity also appears close to the long-term mean. Stochastic population projection using various scenarios showed that, based upon this history, the risk of extinction for the population has declined and is below reasonable thresholds for considering the population to be endangered. The trends in risk suggest that management actions taken since 1990 have probably been effective. Consequently, the conservation management objectives for the Steller sea lion are probably being met. The approach provides a mechanism, based upon experience and scenario analysis, for exploring future policy options and may help to constrain the debate amongst stakeholders about the cost-benefit trade-offs associated with different options.     

Soil-profile distribution of primary and secondary plant-available nutrients under conventional and no tillage

Nutrient distributions under no tillage (NT) compared with conventional disk-and-bed tillage (CT) management in the warm, humid region of the southeastern USA need to be assessed so that future placement, quantity, and type of fertilizers can be altered, if necessary, to efficiently match crop demands. We determined soil-profile distributions of pH, N, P, S, K, Ca, Mg, Na, Zn, Fe, Mn, and Cu to a depth of 0.9 m at the end of 8.5 years of continuous CT and NT management on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas. Most dramatic changes occurred within the 0–0.05 m depth, where soil under NT had lower pH, Fe, and Cu than under CT, but greater P, K, Zn, and Mn. Greater P and K under NT than under CT also occurred below the till-zone (0.15–0.3 m). At a depth of 0–0.3 m, soil under NT contained greater amounts of extractable P, K, Zn, Fe, Mn, and Cu than under CT. Nitrogen fertilization had little effect on nutrient distributions, except resulting in greater extractable K at 0–0.05 m and greater nitrate at 0–0.15 m. Few changes in soil-profile distributions were observed for extractable S, Ca, Mg, and Na. Long-term continuous use of NT on this fine-textured, high-fertility (except for N) soil had no apparent adverse effects on nutrient distributions relative to CT, but enhanced conservation and availability of P, K, Zn, Fe, Mn, and Cu near the soil surface where crop roots proliferate.     

Macroinvertebrates in North American tallgrass prairie soils: effects of fire, mowing, and fertilization on density and biomass

The responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils.     

Variation in quality parameters between and within 14 Nordic tree fruit and berry species

Abstract

A 3-year study was carried out to investigate quality parameters in 14 tree fruit and berry species grown in southern Norway. The species were blueberry, apple, aronia, sour cherry, sweet cherry, red raspberry, strawberry, blackcurrant, gooseberry, red currant and elderberry, harvested along with wild bilberry, cloudberry and lingonberry. Significant differences between species were identified for all quality parameters. The coefficient of variation between species was lowest for pH (12.5%), dry matter (18.9%) and soluble solids (25.3%), followed by titratable acids (59.3%), total phenolics (83.8%), antioxidant capacity FRAP (85.7%) and antiradical power by the DPPH-assay (97.8%), total monomeric anthocyanins (132%) and ascorbic acid (137%). Average coefficient of variation within species were lower and ranged from 4 (pH) to 62% (ascorbic acid). Only the FRAP values were significantly affected by harvesting year with lower levels in 2004 than in 2005 and 2006. There were significant interactions between species and harvesting year for dry matter, soluble solids, pH, ascorbic acid and FRAP. The results indicate generic ranges in composition within species independent upon growing location and climate, and the composition of the tree fruits and berries is not likely to deviate from these ranges. It is concluded that desirable composition of tree fruits and berries and their products should primarily be achieved by selection among species rather than searching fors broadened variation within individual species.     

Enhanced establishment and growth of giant cardon cactus in an eroded field in the Sonoran Desert using native legume trees as nurse plants aided by plant growth-promoting microorganisms and compost

To evaluate the feasibility of long-term desert reforestation technology of mixed vegetation, cardon cactus (Pachycereus pringlei) seedlings from indoor and outdoor nurseries were planted in the field adjacent to one seedling of potential legume nurse trees: mesquite amargo (Prosopis articulata), yellow palo verde (Parkinsonia microphylla), and blue palo verde (Parkinsonia florida). Some of the planting holes were also supplemented with common dairy compost. Additionally, the combinations of legume tree–cactus were inoculated with either a consortium of desert arbuscular mycorrhizal (AM) fungi, plant growth promoting bacteria (PGPB; the diazotroph Azospirillum brasilense Cd, and the phosphate solubilizer Paenibacillus sp.), or a mixture of all. The field experiments were evaluated periodically during 30 months for survival and growth. Cardons reared in an outdoor screen house survived better in the field than those reared in a controlled growth chamber and hardened later outdoors. Association with any legume nurse tree increased survival and enhanced growth of untreated cardons. For cardons growing alone, application of either compost, AM fungi, and all the treatments combined increased survival. For these plants, no treatment affected plant growth during the first 3 months after transplanting. Later, all treatments, except for AM fungi, enhanced plant growth. However, only 2 years after transplanting the enhanced growth effect of AM fungi was also significant. In the presence of the legume nurse trees, transient positive effects on cardon growth were recorded. General evaluation after 30 months of cultivation showed that the treatments positively affected cardon growth when growing alone or in combination only with mesquite amargo but not with the other two legume trees. This study proposes that young legume trees have the capacity to enhance survival and growth of cardon cactus, depending on the legume cactus combination. Additional treatments such as compost or PGPB can either amplify the effect or else attenuate it.     

Karyotypic and genome size variation in Cajanus cajan (L.) Millsp. (pigeonpea) and some wild relatives

Detailed karyotypes and 4C DNA amounts have been studied in five cultivars of Cajanus cajan and 20 species belonging to Cajanus, Rhynchosia, Dunbaria, Flemingia and Paracalyx. C. cajan shows intraspecific variability and its karyotype is most similar to that of C. cajanifolius (sect. Cajanus) in the morphology and number of satellite chromosomes and the lack of any correlation between chromosome size within the complement and asymmetry. Karyotypes of C. lineatus and C. sericeus belonging to sect. Atylia are similar with respect to maximum r-index and the ratio of longest and shortest chromosomes in their respective complements. C. acutifolius (sect. Frutocosa) is distinct in having a very low ratio (1.44) between the longest and the shortest chromosomes, while in C. albicans, C. goensis, C. scarabaeoides (sect. Cantharospermum) there is no chromosome pair with r-index >2.0. C. mollis and C. volubilis (sect. Volubilis) show similarity with regard to ratio between the longest and the shortest chromosomes and a distinct chromosome pair with an arm ratio of 2.7 and C. platycarpus is distinct (sect. Rhynchosoides) in having the smallest ratio (1.36) between the longest and the shortest chromosomes. 4C DNA amounts in Cajanus and Rhynchosia vary between 3.28 pg to 11.69 pg and 4.92 pg to 11.13 pg respectively, while in Dunbaria, Flemingia and Paracalyx these vary between 4.70 and 7:06 pg. In the genus Cajanus karyotypic features and 4C DNA amounts agree with the sectional classification and bring out a close relationship between C. cajan and C. cajanifolius. This is supported by studies based on seed protein patterns, isozyme analysis, trypsin and chymotrypsin inhibitor patterns, RFLP and RAPD data and crossability relationships. A clear relation between DNA amount and abnormalities effecting the extent of pairing and recombination in interspecific hybrids shows the importance of this study in developing future breeding programme involving C. cajan and its wild relatives that are of potential value.     

Potassium Fixation and Release Characteristics in Rhizosphere and Nonrhizosphere Soils for a Rapeseed–Rice Cropping Sequence

Potassium (K) fixation and release in soil are important factors in the long-term sustainability of a cropping system. Changes in K concentration and characteristics of K fixation and release in rhizosphere and nonrhizosphere soils in the rapeseed (Brassica napus L.)–rice (Oryza sativa L.) rotation were investigated using a rhizobox system. The concentrations of different forms of K in both rhizosphere and nonrhizosphere soils decreased with plants compared to without plants, regardless of K fertilizer application. Potassium uptake by crops mainly came from the rhizosphere soil. In the treatment without K fertilizer (–K), the main form of K supplied by the soil to the crops was 1.0 mol L^?1 nitric acid (HNO₃) nonextractable K, followed by nonexchangeable K, and then exchangeable K. In the treatment with K fertilizer (+K), the main K forms supplied by the soil to the crops were exchangeable K and nonexchangeable K. The amount and rate of K fixation after one cycle of the rapeseed–rice rotation was greater in rhizosphere soil than in nonrhizosphere soil. The amount and rate of K fixation of soil in the +K treatment were significantly less than in the –K treatment. The cumulative amounts of K released with 1.0 mol L^?1 ammonium acetate (NH₄OAc) and 1.0 mol L^?1 HNO₃ extraction increased with the increasing numbers of extractions, but the K-releasing power of soil by successive extraction decreased gradually and finally became almost constant. The release of K was less in rhizosphere soil than in nonrhizosphere soil. The release of K in the +K treatment was similar to that in the –K treatment in rhizosphere soil, but the K release in nonrhizosphere soil was greater with the +K than the –K treatment. Overall, the information obtained in this study will be helpful in formulating more precise K fertilizer recommendations for certain soils.