毛竹qRT-PCR分析中内参基因的选择

实时荧光定量PCR(quantitative Real-time PCR,qRT-PCR)是目前研究基因表达的常用方法,而在特定的实验材料及条件下选择合适的内参基因是准确分析目标基因相对表达量的首要条件。本研究以毛竹(Phyllostachys edulis)的根、茎、叶和笋等器官和组织为实验材料,通过qRT-PCR技术对5种常用内参基因:甘油醛-3-磷酸脱氢酶(glyceraldehyde-3-phosphate dehydrogenase,GAPDH)、肌动蛋白(actin,ACT)、热休克蛋白(heat shock protein,HSP)、18S核糖体RNA(18S ribosomal RNA,18S r RNA)和真核起始因子4α(eukaryotic initiation factor 4α,e IF-4α)在毛竹不同器官和组织中的表达情况进行了分析。经Ge Norm、Norm Finder和Best Keeper 3个软件对比分析发现,对5种常用内参基因而言,在利用qRT-PCR分析比较毛竹不同叶片之间的基因表达差异时,可选取e IF-4α作为校正内参基因;比较笋不同部位之间的基因表达差异时,可选取18S r RNA或ACT作为校正内参基因;而比较毛竹根、茎、叶不同器官组织分化中的基因表达差异时,可选取18S r RNA作为校正内参基因。而上述发现与多数文献中把ACT作为毛竹唯一内参基因的研究不一致。本研究为在毛竹qRT-PCR分析中选择合适的内参基因提供了理论依据。     

利用实时荧光定量PCR筛选新蚜虫疠霉内参基因

内参基因的准确选择是利用实时荧光定量PCR进行准确分析基因相对表达量的前提。虫霉目真菌新蚜虫疠霉(Pandora neoaphidis)是重要蚜科专化性病原真菌,经常引发多种作物上蚜虫种群的流行病。本研究通过实时荧光定量PCR分析了新蚜虫疠霉ARSEF 5403中3个传统管家基因18Sr RNA(18S)、28Sr RNA(28S)和延伸因子1α相似蛋白(elongation factor-1 alpha-like protein,EF1)m RNA表达差异情况,并利用ge Norm、Norm Finder和Best Keeper软件综合分析了其在4个生长阶段(分生孢子、萌发管时期、短菌丝和长菌丝)和3种营养条件(GLEN培养基、OS-SDB培养基和Grace培养基)下表达的稳定性。结果表明,基于公共数据库序列设计的候选内参基因的引物具有良好的扩增效率和特异性。经ge Norm软件分析,新蚜虫疠霉在不同生长阶段和不同营养条件下3个候选内参基因的平均表达稳定性(M值)分别为:18S(0.457)28S(0.534)EF1(0.749)和18S(0.389)28S(0.557)EF1(0.607)。利用Norm Finder软件分析,新蚜虫疠霉不同生长阶段和不同营养条件下3个候选内参基因的平均M值分别为:18S(0.084)28S(0.264)EF1(0.509)和18S(0.118)28S(0.355)EF1(0.403)。而Best Keeper软件分析得到的稳定性等级有所差异,在不同生长阶段和不同营养条件下候选内参基因28S表达最稳定,18S次之,EF1最不稳定。综合分析3款软件对荧光定量PCR结果的稳定性等级的平均值,得出在不同生长阶段和不同营养条件下候选内参基因18S表达最为稳定。筛选出的18S可作为分析新蚜虫疠霉基因表达差异的一个较为可靠的内参基因,同时为后续研究新蚜虫疠霉的生长、毒力相关基因的表达分析研究提供技术支持。     

草鱼MYH mRNA表达量分析中采用的内参基因稳定性比较

本研究分别以β-actin、18SrRNA和GAPDH为内参基因,采用实时荧光定量PCR对草鱼早期发育时期肌球蛋白重链（myosin heavy light,MYH）基因的mRNA表达量进行分析,并比较不同内参基因对MYH基因mRNA表达水平检测结果的准确性。研究结果表明,以β-actin和GAPDH作为内参,MYH基因mRNA表达水平完全一致,其表达量从原肠到仔鱼阶段逐次递增,仔鱼与原肠期阶段相比表达量差异显著;当采用18S rRNA作为内参时,MYH基因mRNA在发育阶段的表达量呈不稳定状态。因此,β-actin和GAPDH均可作为内参基因,用于草鱼早期发育中MYH基因mRNA的相对定量研究;而18S rRNA作为内参时,可能会对检测结果造成偏差。本研究不仅准确的揭示了草鱼MYH基因mRNA的表达特征,并且为荧光定量PCR技术在鱼类基因表达研究方面提供了有价值的参考。     

柳枝稷根组织实时定量PCR分析中内参基因的选择

选择表达稳定性高的内参基因是提高实时荧光定量PCR分析(qRT-PCR)准确性的重要条件。本研究以能源植物柳枝稷(Panicum virgatum L.)根组织为材料,通过不同非生物条件胁迫,利用qRT-PCR技术检测UBQ1(泛素基因)、ACT2(肌动蛋白基因)、UBQ2(泛素基因)、TUB(β微管蛋白基因)、GAPDH(甘油醛-3-磷酸-脱氢酶基因)、CBP20(类胡萝卜素结合蛋白基因)、UCE2(泛素接合酶基因)、18S rRNA1(18S核糖体RNA基因)、NAC(NAC域蛋白基因)和CYP2(亲环蛋白基因)10个内参基因的mRNA的表达情况,并运用Delta-Ct method,Genorm(ver.3.5)、Bestkeeper(ver.1.0)和NormFinder(ver.0.953)软件综合分析10个内参基因的表达稳定性。结果显示,在不同的非生物环境胁迫条件下,最适合作为柳枝稷根组织研究的内参基因各不相同。10个内参基因平均表达稳定由高到低排序为:ACT2,TUB,UCE2,CBP20,CYP2,UBQ2,18S rRNA1,NAC,UBQ1,GAPDH。在干旱胁迫条件下,ACT2基因表达稳定性最高;在盐胁迫和热胁迫条件下,18S rRNA1基因表达稳定性最高;在冷胁迫和涝胁迫条件下,ACT2基因表达稳定性最高。经软件综合分析显示,ACT2、TUB和UCE2基因最适合作为柳枝稷非生物胁迫研究的内参基因;UBQ1和GAPDH基因最不合适作为内参基因。该研究结果可用于柳枝稷非生物胁迫下各种基因表达的进一步研究。     

牡丹实时定量PCR分析中内参基因的选择

实时荧光定量PCR(qPCR)是目前研究基因定量表达的重要方法,根据特定实验材料及条件选择qPCR分析中合适的内参基因对于准确校正目的基因的表达至关重要。本研究以牡丹(Paeonia suffruticosa Andr.)不同组织(根、茎、叶和花瓣)、切花开放不同时期及不同处理(乙烯或葡萄糖处理)的花瓣为材料,利用qPCR技术探讨了5种常用看家基因:β-微管蛋白基因(β-tubulin)、泛素基因(ubiquitin)、甘油醛-3-磷酸-脱氢酶基因(GAPDH)、肌动蛋白基因(actin)及18S核糖体RNA(18S rRNA)的表达情况,各看家基因均能特异扩增并显示较高的扩增效率。经geNorm和NormFinder程序统计学计算处理,综合分析结果显示,在牡丹不同组织或切花开放不同时期花瓣中,ubiquitin表达最为稳定;在不同处理的切花花瓣中,GAPDH表达最为稳定,二者分别适宜作为相应条件下的内参基因。本研究认为,各实验条件下使用ubiquitin和GAPDH两个表达最稳定的基因组合,即可获得更为精确的基因表达结果。本研究结果对牡丹中关键基因的定量表达分析具有重要的实用价值。     

玉兰盐胁迫下qRT-PCR分析中内参基因的筛选

选择合适的内参基因可以提高q RT-PCR分析相关基因表达的准确性。本研究以玉兰(Magnolia denudata)实生苗在盐胁迫下的根、茎、叶为材料,选取常用的13个内参基因:肌动蛋白(actin,ACTIN)、亲环蛋白(cyclophilin,CYP)、延伸因子1α蛋白(elongationfactors-1α,EF-1α)、甘油醛-3-磷酸脱氢酶(glyceraldehyde-3-phosphat dehydrogenase,GAPDH)、GTP结合蛋白(GTP binding protein,GBP)、NAC域蛋白(NAC domain protein,NAC)、异柠檬酸脱氢酶(NADP-isocitrate dehydrogenase,NADP)、翻译延伸因子(translation elongation factors,TEF)、泛素化酶基因(ubiquitin-conjugating enzyme,UBC)、多聚泛素蛋白(polyubiquitin protein,UBQ)、微管蛋白(α-tubulin alphaα,α-TUB)、β微管蛋白(tubulin beta,β-TUB)、18S核糖体RNA(18S ribosomal RNA,18S)作为候选内参基因,设计引物,通过普通PCR和溶解曲线验证引物特异性;结合ge Norm、Norm Finder和Best Keeper软件分析筛选最佳内参基因,进一步通过2个目的基因:纤维素合成酶类似蛋白D(cellulose synthase-like D,CSLD)和1,4-β-d-葡聚糖酶(endo-1,4-beta-d-glucanase,KOR)对筛选得到的内参基因进行验证。结果显示,13个内参基因PCR产物条带清晰单一,引物扩增效率均在95%到105%之间,且溶解曲线呈现明显的单一峰,表明引物特异性良好;3个内参软件ge Norm、Norm Finder和Best Keeper综合分析得到稳定性排名前3的内参基因为GBP、UBQ和UBC,而18S为最差的内参基因。进一步选取GBP、UBQ、UBC 3个基因的组合以及稳定性差的18S和GAPDH基因,对不同组织中的CSLD和KOR基因进行相对表达分析,结果表明,两个目的基因相对于3个稳定的内参基因及其组合显示出一致的相对表达量,而不稳定的内参基因18S和GAPDH没有对表达数据进行有效的标准化,结果存在偏差。由此可见,GBP、UBQ和UBC可以作为玉兰盐胁迫下不同组织器官中表达的稳定内参。本研究结果将为木兰属植物在逆境中相关目的基因的定量表达研究提供重要的参考依据。     

铜胁迫下天蓝苜蓿根组织实时定量PCR内参基因的选择

豆科植物-根瘤菌共生体系因固氮能力卓越,肥土效应明显,常被作为先锋植物进行环境修复。利用qRT-PCR分析铜胁迫下天蓝苜蓿(Medicago lupulina L.)与根瘤菌(Sinorhizobium meliloti,CCNWSX0020)共生固氮过程中差异基因时,由于环境中铜离子差异可能使持家基因表达不稳定,因此需要筛选合适的持家基因作为内参。本研究选取8个天蓝苜蓿的持家基因(肌动蛋白(beta actin,ACT)、组蛋白(histone H2A,H2A)、核糖体蛋白18S(ribosomal 18S,18S)、微管蛋白(tubulin beta,TUB)、泛素连接酶(ubiquitin,UBI)、延伸因子1(elongation factor 1,EF1)、甘油醛-3-磷酸脱氢酶(glyceraldehyde-3-phosphate dehydrogenase,GAPDH)和亲环蛋白(cyclophilin,CYP))作为候选内参基因,人工模拟不同水平铜(浓度分别为50、100、150和200 mg/kg)污染,以接种根瘤菌后30 d的天蓝苜蓿根为材料,筛选最佳内参基因。经引物特异性及PCR扩增效率检测,各候选内参基因引物均符合稳定性筛选要求。荧光定量PCR分析结果表明,8个候选内参基因的表达水平和稳定性随铜离子浓度不同而呈现差异。在线评估所有样品中候选内参基因表达稳定性,结合geNorm软件分析最佳内参基因组合数目,结果发现,最适内参基因组合为GAPDH和EF1;分别在线评估不同铜浓度处理下候选内参基因表达稳定性,结果表明,低浓度铜(≤50 mg/kg)处理下最佳内参基因为GAPDH,中高浓度铜(≥100 mg/kg)处理时最佳内参基因为UBI。本研究结果为铜胁迫下天蓝苜蓿共生结瘤过程中差异基因的表达分析提供了基础资料,同时为其他重金属胁迫下内参基因的筛选提供了参考和借鉴。     

小麦条锈菌实时荧光定量PCR分析中内参基因的选择

选择合适的内参基因是利用实时荧光定量PCR准确分析基因相对表达量的先决条件.基于现有对内参基因的研究,本研究挑选出10个基因作为小麦条锈菌(Puccinia striiformis f.sp.tritici)的候选内参基因.经过PCR扩增效率筛选,8个基因符合要求可用于稳定度的筛选,这些基因包括泛素连接酶(UBC、泛素连接酶E2(UBCE2)、核糖体蛋白SS(RPS5)、α微管蛋白(TUBA)、β肌动蛋白(ACTB)、β微管蛋白(TUBB)、延伸因子1(EF1)和延伸因子3(EF3).本研究以两种小麦条锈菌(CYR32和Pst78)的夏孢子、萌发芽管分别接种两个小麦(Triticum aestivam)品种(CYR32/XZ9104和Pst78/AvS)后0.5、3和14 d的样品为材料,利用实时荧光定量PCR技术,检测了这8个持家基因在不同发育阶段的小麦条锈菌中的表达情况.经geNorm软件分析发现,3个持家基因在样品中的表达趋势与小麦条锈菌的侵染过程相符合.ACTB、TUBB和TUBA的组合可作为检测小麦条锈菌基因表达的内参基因.     

黄秋葵实时荧光定量PCR内参基因的克隆与筛选评价

为筛选黄秋葵实时荧光定量PCR的稳定内参基因,本研究以绿白1号为试验材料,根据黄秋葵RNA-seq数据库,筛选并验证获得18SrRNA、ACT、EF-1α、TUA、TUB、GAPDH等6个内参基因ORF序列;以黄秋葵不同组织、不同发育时期果实、不同发育时期叶片和低温、高温、干旱胁迫处理的叶片为材料,利用实时荧光定量PCR技术分析测定基因表达量,并结合GeNorm、NormFinder和BestKeeper软件评价6个内参基因的稳定性。结果表明,6个基因在不同组织、各发育阶段及不同胁迫下均有表达,但表达稳定性不尽相同,其中,EF-1α在黄秋葵果荚发育、高温胁迫下表达稳定性最好;18SrRNA在黄秋葵各组织、叶发育和干旱胁迫下表达稳定性最优;ACT在低温胁迫下表现最稳定。此外,在29个处理中,18SrRNA、EF-1α、ACT表达均较稳定,可以用于荧光定量表达分析。本研究结果为黄秋葵基因功能分析和调控机理研究提供了基础。     

绵羊口蹄疫病毒整联蛋白受体αv亚基基因不同组织表达差异

为了建立检测绵羊口蹄疫病毒(Foot andmouth disease virus,FMDV)整联蛋白受体αv亚基基因mRNA相对表达量的荧光定量RT-PCR方法,本研究根据报道的绵羊FMDV整联蛋白受体αv亚基(integrin,alphaV,ITGAV)基因序列设计实时定量PCR引物,以β-αctin为内参基因,采用相对荧光定量RT-PCR方法,检测分析αv基因在绵羊体内不同组织器官中的mRNA表达谱.结果显示αv基因在绵羊19种组织中均有不同程度的转录表达,在乳腺组织中表达量最高,蹄组织次之,肌肉组织最少,卵巢、瘤胃、气管、小肠、肺等组织上也有不同程度的表达.本研究成功建立了检测FMDV整联蛋白受体αv亚基基因在绵羊不同器官组织中mRNA表达水平的相对荧光定量RT-PCR方法,并明确了αv基因在不同组织间的表达差异,为FMDV组织嗜性研究及分子生物学检测方法的建立提供了资料.     

“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.