小麦WDHN1基因的克隆、表达及功能分析

YSK2型脱水素(dehydrins,DHNs)是植物中存在最多的DHNs形式,参与植物响应各种非生物逆境胁迫.为了研究YSK2型DHN的功能,从小麦(Triticum aestivum)中克隆了WDHN1基因(GenBank No.KR709259),该基因编码区序列总长491 bp,含两个外显子和一个内含子,编码133个氨基酸;存在4个保守区域,即1个Y片段、1个S片段和2个K片段,与节节麦(Aegilops tauschii) DHN (EMT30992)亲缘关系最近.通过PCR扩增得到WDHN1启动子序列,该启动子存在2个脱落酸应答元件(abscisic acid (ABA)response element,ABRE)和3个MBS(MYB binding site)生物胁迫响应元件.通过qRT-PCR分析其非生物胁迫下的表达模式,结果表明,在低温、NaC1、ABA和PEG 6000胁迫下,小麦WDHN1基因表达均表现为先上升后下降的趋势,分别于6、60、12和48 h时表达量最高.组织特异性表达分析表明,WDHN1基因在小麦开花后22 d的胚芽中表达量最高,具有明显的组织特异性.将WDHN1基因片段连接于原核表达载体pET28a中,转化大肠杆菌(Escherichia coli) BL21(DE3),用异丙基硫代半乳糖苷(isopropyl β-D-1-thiogalactopyranoside,IPTG)诱导表达,获得20 kD的WDHN1蛋白.对重组大肠杆菌WDHNl-pET28a-BL21(DE3)及其总蛋白进行非生物胁迫,结果表明,WDHNl蛋白还可以阻止蛋白聚合引起的蛋白变性,提高非生物胁迫下大肠杆菌的耐受性及乳酸脱氢酶(lactic dehydrogenase,LDH)的稳定性.研究结果为进一步利用该基因进行小麦抗性改良提供了理论依据.     

小麦TaWRKY51基因的克隆、表达分析和转基因功能鉴定

WRKY是植物中特有的锌指型转录因子,其广泛参与植物对生物及非生物胁迫的响应过程.本研究从小麦(Triticum aestivum L.)中分离出一个新的WRKY转录因子基因TaWRKY51,其全长cDNA序列长度为1295 bp,其中开放阅读框(ORF)为942 bp,编码一个由313个氨基酸组成的多肽.用半定量RT-PCR进行表达谱分析,结果显示,TaWRKY51基因在分蘖节、叶和根系中的表达水平较高,并且受干旱胁迫诱导上调表达.在拟南芥(Arabidopsis thaliana)中过量表达TaWRKY51基因导致转基因株系侧根数目明显增多,并且对ABA、干旱和盐等胁迫处理的敏感性增加,表明该基因可能在植物响应非生物逆境胁迫信号传导过程中起负调控作用.本研究有助于揭示TaWRKY51基因调控植物侧根发育及响应非生物逆境胁迫的分子机制.     

谷子CIPK基因(Seita.5G145900)对非生物逆境的响应

在谷子基因组中鉴定出一个CIPK(Seita.5G145900,命名为SiCIPK19)基因。为揭示SiCIPK19对逆境胁迫的响应,对其基因结构、蛋白特征、功能、进化等性状进行了系统的分析和预测,并用实时定量PCR(RT-qPCR)检测了其在谷子苗期不同逆境及关键生育期干旱胁迫下的表达。结果表明,SiCIPK19基因位于谷子5号染色体,基因组序列长1 353 bp,编码450个氨基酸,基因无可变剪切,且不含内含子。功能域分析和多序列比对发现,SiCIPK19蛋白具有非常保守的序列结构,与其他植物CIPK蛋白也非常相似。RT-qPCR分析表明,SiCIPK19基因被聚乙二醇6000(PEG 6000)、ABA、高盐和低温胁迫强烈诱导。此外,SiCIPK19基因在谷子拔节期、抽穗期和灌浆期干旱条件下参与了对干旱胁迫的响应,推测该基因参与谷子对非生物逆境的应答,尤其在抽穗期和灌浆期干旱胁迫应答中发挥重要作用。本研究结果为进一步分析CIPK基因逆境应答机制,以及利用基因工程方法改善谷子抗逆性和提高产量提供了理论支持。     

巴西橡胶树磷脂酰肌醇转移蛋白cDNA的克隆及其序列分析

本文从巴西橡胶树（Hevea brasiliensis）差减cDNA文库中筛选到一个与磷脂酰肌醇转移蛋白（phos-phatidylinositol transfer protein）同源性较高的基因片段,并根据该基因片段序列信息,设计特异性引物,采用cDNA末端快速扩增技术RACE（rapid amplification of cDNA ends）进行差异片段的5＇和3＇端的扩增,并获得长度为1081bp的全长cDNA克隆R291（GenBank登陆号：AY589690）。序列分析表明,该基因包含702bp的开放阅读框,编码234个氨基酸,推测其蛋白质的分子量为26.8kD,等电点为6.51,有一个的跨膜螺旋区（氨基酸位点为83～103）。R291基因含有一个脂质结合保守区（Sec14p-like lipid-binding domain）,具有CRAL-TRIO脂质结合结构域,推测该基因是一个磷脂酰肌醇转移蛋白基因。该基因的克隆将为橡胶树磷脂酰肌醇代谢的研究奠定了基础,将有助于进一步了解磷脂酰肌醇代谢与胶乳再生之间的关系。     

小麦TaGAPC1基因及其启动子的克隆与功能分析

甘油醛-3-磷酸脱氢酶(glyceraldehyde-3-phosphate dehydrogenase, GAPDH)是糖酵解过程中的关键酶。作为GAPDH的亚型,GAPC(cytosolic glyceraldehyde-3-phosphate dehydrogenase)催化3-磷酸甘油醛氧化生成1,3-二磷酸甘油酸,但是关于GAPC在非生物胁迫应答中作用的研究却并不充分。本研究从中国春小麦(Triticum aestivum)中克隆出了TaGAPC1基因(GenBank No. KU246046),其编码337个氨基酸,并克隆出基因上游973 bp的序列,将其命名为P973。通过融合绿色荧光蛋白(green fluorescent protein,GFP)报告基因,使用基因枪法瞬时转化洋葱(Allium cepa)表皮细胞进行亚细胞定位,结果显示TaGAPC1蛋白定位于细胞膜上。使用实时荧光定量PCR(quantitative real-time PCR, qRT-PCR)技术,分析TaGAPC1基因在根、茎、叶中,以及干旱(PEG8000)、盐(NaCl)、脱落酸(abscisic acid, ABA)和低温(4℃)非生物胁迫下的表达模式。结果表明TaGAPC1基因在叶、根、茎中的表达量依次下降,在PEG8000、NaCl和ABA胁迫下的表达量显著上升,但对4℃的响应不明显。根据PLACE (http://www.dna.affrc.go.jp/PLACE/)和PlantCARE (http://bioinformatics.psb.ugent.be/webtools/plantcare/html/)数据库分析,P973启动子序列中包含响应干旱、ABA、低温和创伤等胁迫的顺式作用元件,如干旱应答元件(drought-responsive element,DRE)、激素应答元件包括ABA应答元件(ABA-responsive element, ABRE)、MYB结合位点(MYB-binding site, MBS)和WUN-motif等。根据顺式作用元件的分布,扩增得到5个启动子5'端缺失片段,分别命名为P844、P738、P605、P475和P256。构建6条启动子序列融合β-葡萄糖苷酸酶基因(β-glucuronidase, GUS)的表达载体,并瞬时转化烟草(Nicotiana batacum)植株,测定PEG8000、NaCl、ABA和4℃胁迫下各启动子驱动的GUS酶活。结果表明,-973~-605启动子区域在TaGAPC1基因应答PEG8000和NaCl胁迫中具有关键作用,-973~-475启动子区域对应答ABA胁迫至关重要。本研究从分子水平初步阐释了TaGAPC1与非生物胁迫应答的关系,为深入探讨其抗逆的分子机制奠定了基础。     

非生物胁迫下W-box突变对小麦TaGAPC5基因启动子活性的影响

小麦(Triticum aestivum)胞质甘油醛3-磷酸脱氢酶(cytosolic glyceraldehyde-3-phosphate dehydrogenase,GAPC)Ta GAPC5基因在干旱等非生物胁迫下显著表达。序列分析表明,Ta GAPC5基因启动子区包含3个W-box顺式作用元件。本实验利用PCR定点突变技术对Ta GAPC5基因启动子区-640处W-box单独突变、-640、-700两处W-box突变和-640、-700、-997处W-box均突变,将这3种突变的启动子分别与植物表达载体p C0390-GUS融合表达,利用农杆菌(Agrobaoterium tumefaciens)介导法转化烟草(Nicotiana tabacum),对转化后的烟草分别进行正常条件下培养和100 nmol/L脱落酸(abscisic acid,ABA)、20%PEG8000胁迫处理。组织化学染色结果显示,这3种突变后的启动子序列均具有一定的启动子活性。烟草叶片GUS酶活检测结果表明,在正常生长条件下,Ta GAPC5基因启动子-640处W-box单独突变对启动子活性影响不大,-640、-700、-997三处W-box均突变Ta GAPC5基因启动子活性显著降低(P0.01);在100 nmol/L ABA诱导下,-640处W-box单独突变、-640、-700两处W-box突变和-640、-700、-997处W-box均突变均可显著降低Ta GAPC5基因启动子活性(P0.01);在PEG胁迫条件下,Ta GAPC5基因启动子-640处W-box单独突变和-640、-700、-997三处W-box均突变可显著降低该基因启动子活性(P0.01)。因此表明-640、-700、-997处W-box对小麦Ta GAPC5基因启动子活性有一定影响,其中在100 nmol/L ABA、20%PEG8000胁迫条件下其影响较大,推测Ta GAPC5基因启动子序列中W-box元件可能参与非生物胁迫下小麦Ta GAPC5基因的表达调控。这一研究结果可为小麦Ta GAPC5基因在非生物胁迫下的表达调控研究提供重要线索。     

玉米乙烯应答元件结合蛋白基因启动子克隆与功能验证

为了给玉米转基因研究提供更多的非生物逆境诱导启动子,寻找只在逆境胁迫条件下适当驱动外源抗逆基因的表达,在生物信息学分析的基础上,克隆与水稻DREB1B转录因子基因同源的玉米乙烯应答元件结合蛋白基因sb CBF6的启动子psb CBF6,在非生物逆境应答元件分析和实时定量PCR验证其非生物逆境胁迫响应特性后,用以构建驱动报告基因GUS的表达载体,并使用基因枪法转化玉米愈伤组织,通过愈伤组织的GUS荧光值与荧光素酶发光值的比值,评价psb CBF6启动子在非生物逆境胁迫及激素诱导条件下的驱动活性。结果表明,sb CBF6基因在各种非生物逆境胁迫下差异表达。psb CBF6启动子长1 479 bp,存在多种与非生物逆境胁迫应答相关的调控元件,可在非生物胁迫条件下驱动外源抗逆基因在转基因植物中诱导表达。试验结果为研究抗逆转基因玉米提了供参考。     

植物逆境microRNA的研究进展

MicroRNA（miRNA）在生物中广泛存在,在调控植物生长和发育方面起重要作用。多种非生物逆境会影响植物生长,不同逆境胁迫还会使植物相应的miRNA诱导或下调表达,有时一种miRNA会同时受几种逆境胁迫影响。本文综述了植物中参与温度、水分、盐、养分、氧化、ABA、重金属及其它非生物逆境胁迫的miRNA及其作用机制的研究进展。     

棉花转录因子基因(GhMYB11)的克隆与表达分析

MYB基因家族在植物应对外界生物和非生物胁迫的过程中有重要的调控作用.本研究利用二倍体雷蒙德氏棉(Gossypium raimondii)基因组数据库,从陆地棉(G.hirsutum)品种鲁棉研32号中克隆到一个新的MYB转录因子GhMYB111(GenBank登录号:HQ234875.1),Cdna全长1 001 bp,开放阅读框828bp.通过与模式植物拟南芥(Arabidopsis thaliana)和主要作物小麦(Triticum aestivum L.)、玉米(Zea mays L.)、水稻(Oryza sativa L.) MYB蛋白的氨基酸序列比对发现,GhMYB 11蛋白与拟南芥中脱落酸(abscisic acid,ABA)合成和信号传导的重要基因AtMYB13/14编码的蛋白高度相似(E值分别为7e-83和1e-90),含两个高度保守的MYB结构域R2R3及一个转录激活结构域.实时定量PCR分析发现,GhMYB 11基因在黄萎病菌(Verticillium dahliae)侵染、干旱、盐和氧化胁迫处理后的棉花幼苗叶片中表达显著上调.GhMYB11基因可能在棉花生物和非生物胁迫反应中起重要调控作用,是陆地棉品种抗逆性遗传改良的重要候选基因.本研究为利用基因工程手段提高棉花抗逆性提供了基础材料     

南方型紫花苜蓿叶片响应盐胁迫蛋白质组和转录组关联分析

为了从基因和蛋白质水平上揭示南方型紫花苜蓿适应盐胁迫环境的分子机制,以南方型紫花苜蓿Millennium为材料,对正常培养和盐胁迫条件下的2个样品叶片进行转录组和蛋白质组关联分析。结果表明,定量蛋白和基因关联系数为0.2485;变化趋势相反差异蛋白和基因表达的关联系数为-0.2440;变化趋势相同差异蛋白质和基因表达的关联系数为0.8122。鉴定出109个与差异基因表达趋势相同的差异蛋白,其中77个上调,32个下调,这些差异蛋白功能涉及光合作用、抗氧化物、信号传递、翻译后修饰、翻译和分子伴侣、胁迫防御、能量产生与转运、代谢和其它未知功能蛋白等。下调表达的蛋白主要与光合作用相关,而上调表达的蛋白主要参与了抗氧化物、信号传递和胁迫防御等。此外,关联发现了与紫花苜蓿盐胁迫响应相关的III类过氧化物酶、铁蛋白、谷胱甘肽S-转移酶、磷脂酰肌醇特异性磷脂酶C、LRR类受体激酶、ABA反应蛋白、钙联接蛋白2、液泡H+-ATP酶C亚基和NADP-苹果酸酶等差异蛋白。本研究通过高通量多组学数据的关联分析,发现一些可能作为紫花苜蓿耐盐潜在靶标蛋白(基因),这为深入认识紫花苜蓿盐胁迫的应答分子调控机制奠定了坚实的基础。     

“绿色革命”以来大气CO2浓度升高对C3作物营养品质的影响

自20世纪60年代"绿色革命"以来,育种技术和农耕技术的发展促进了农作物产量的大幅提升,然而作物的营养品质出现下降趋势。在相似的遗传背景下,大气CO_2浓度升高会使单位体积农作物产品的营养元素含量下降,因此"绿色革命"至今,农作物产品的营养元素下降可能受大气CO_2浓度升高影响。通过植物生长箱模拟"绿色革命"初期和目前的大气CO_2浓度水平(310μmol/mol和400μmol/mol),针对主要C_3作物水稻、小麦和大豆,研究"绿色革命"以来大气CO_2浓度升高对其籽粒的C、N、Fe、Zn元素含量的影响,结果表明:CO_2浓度升高对3种作物籽粒的C元素含量几乎没有影响,变化幅度在±1.5%之间;籽粒的N、Fe、Zn元素含量普遍呈现下降趋势,但均未达到显著水平。     

Potential of wild species for genetic enhancement of some semi-arid food crops

Discovery and incorporation of genes from wild species provide means to sustain crop improvement, particularly when levels of resistance in the cultigens are low and virulent strains of pests and pathogens overcome the host plant resistance. The extent of utilization and the potential of the wild genepool for genetic enhancement were reviewed in five important food crops viz. sorghum, pearl millet, chickpea, pigeonpea and groundnut grown in the semi-arid tropics. Introgression from compatible wild germplasm in the primary gene pool resulted in transfer of new cytoplasmic male sterility systems in pearl millet and pigeonpea, development of high protein, cleistogamous flower and dwarf pigeonpea lines and foliar disease resistant groundnut cultivars. Utilization of wild species in secondary and tertiary gene pools has been generally limited due to sterility, restricted recombination or cross incompatibility. Nevertheless, these species are extremely important as they contain high levels of resistance to several important biotic and abiotic stresses. Several of them, like those belonging to the Parasorghum section and the rhizomatous Arachis species are sources of multiple resistances and hold great promise to sustain crop productivity.     

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     

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.     

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.     

Collection and preliminary evaluation of native turfgrass accessions in Italy

Despite a raising interest on turfs in Italy, all theavailable varieties of this kind in the Country are of foreign origin, and areoften poorly adapted to the prevailing climatic conditions. This prompted tobegin a collection activity of indigenous turfgrass species, with the ultimategoal of identifying promising materials for future breeding based on localgenetic resources. The collection was carried out in three areas of Italy, viz.the northern Po Plain, the coastal region of Liguria, and the island of Sardiniathat are characterised, respectively, by subcontinental, warm temperate, andtypical Mediterranean climate. Altogether, 141 sites were visited, yielding 226accessions belonging to eight species of potential interest for turfs:Poa pratensis, Poa trivialis,Festuca rubra, Festuca arundinacea,Lolium perenne, Agrostis stolonifera,Agrostis tenuis, and Cynodon dactylon,this last being a warm-season grass. Poa pratensis andCynodon dactylon were mostly collected in northern Italyand Sardinia, respectively, whereas Festuca arundinacea andLolium perenne were rather ubiquitous. The collection sitesranged from 0 to 1040 m asl, but sites over 750 m wereonly visited in the inner part of Sardinia. All the accessions, collected aswhole plants, were transplanted at Lodi, northern Italy, where they are beingevaluated. Their preliminary evaluation for traits of importance for turf use,such as sward colour and overall quality, highlighted the great variation andthe occurrence of interesting accessions in all species. Other characters wererecorded, bearing specific importance in individual species, and in all casespromising accessions were identified. The germplasm of Festucarubra, Festuca arundinacea, and Loliumperenne proved highly infected by endophytic (symbiotic) fungi of thegenus Neotyphodium.     

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.     

Effect of some fungicide seed treatments on the survival of Bradyrhizobium japonicum and on the nodulation and yield of soybean [Glycine max. (L) Merr.]

Several commercial fungicide seed treatments were evaluated for their possible effect on the survival of Bradyrhizobium japonicum on seeds and on the nodulation and yield of soybeans in a greenhouse and a field experiment. quinolate Pro (carbendazim and oxine copper), Vitavax 200FF (carboxin and thiram), and Monceren (pencycuron) had a small effect or no effect on the survival of B. japonicum and on the nodulation and yield of soybeans. They can thus be considered compatible with soybean seed inoculation. Germipro UFB (carbendazim and iprodione), Apron 35J (metalaxyl), and Tachigaren (hymexazol) decreased B. japonicum survival and the nodulation and yield of soybeans and thus cannot be considered compatible with soybean seed inoculation.     

Leaf position and genotype differences for mineral element concentrations in sorghum grown on tropical acid soil 1

Mineral element deficiencies and toxicities are common problems associated with sorghum [Sorghum bicolor (L.) Moench] production on acid soils. To better understand some of the mineral element problems and the analysis of plant tissue of sorghum plants grown on acid soils, four sorghum genotypes were grown on an acid Oxisol at Carimagua, Colombia limed with dolomite at 2 and 6 Mg ha^‐1.

Samples for mineral element analyses were obtained from leaves at different positions on the four genotypes. Concentrations of P and Mg were highest in the flag leaf (Leaf No. 1) and decreased as the position on the plant declined from the top of the plant for plants grown at 2 Mg lime ha^‐1. Similar decreases in P, Mg, K, and Zn concentrations occurred in plants grown with 6 Mg lime ha^‐1. Concentrations of Ca, S, Si, Mn, Fe, Cu, and Al increased as leaf position declined from the flag leaf for plants grown at 2 and 6 Mg lime ha^‐1. The higher lime supply enhanced Ca and reduced Mn and Fe concentrations in leaves. Differences in mineral element concentrations for the four genotypes used were fairly extensive. The elements to show the greatest range among genotypes were Al and Si and the elements to show the least range among genotypes were P, K, and S. Care should be used in collecting leaf samples for plant analysis and genotypic differences for accumulation of mineral elements should be considered in interpretation of results.