Emergence, spread and strategies for controlling the pandemic of cassava mosaic virus disease in east and central Africa

During the 1990s, an epidemic of an unusually severe form of cassava mosaic virus disease (CMD) has expanded to cover virtually all of Uganda, and substantial areas in the neighbouring countries of Kenya, Tanzania, Sudan and the Democratic Republic of Congo. Losses in the generally sensitive local cassava cultivars have been so great that a common farmer response to the problem has been the temporary abandonment of cassava cultivation. As a consequence, the CMD ‘pandemic’ has had a significant destabilising effect on food security in East Africa. In attempting to combat the problem, vigorous efforts have been made to identify, multiply and disseminate resistant cassava germplasm. This has included cultivars obtained from the breeding programme of the International Institute of Tropical Agriculture (IITA), based in Nigeria, as well as local selections derived from IITA parent stock. Whilst considerable success has been realised in controlling the pandemic in Uganda, addressing the problem at the regional level remains a major challenge. This article reviews progress made in recent years, both in understanding the cause and mechanisms behind the pandemic's expansion, and in developing strategies to control it. Particular attention is drawn to the likely threat the pandemic poses to cassava production in the countries of central Africa, most notably the Democratic Republic of Congo, where insecurity currently impedes an assessment of the problem and the ready implementation of control measures. Scientists and other stakeholders with an interest in CMD management are therefore urged to explore innovative mechanisms that will allow them to develop a more comprehensive approach to CMD control in the region.     

木薯作物遗传资源、生物技术与育种

木薯贮藏根具有提升世界热区人类食物营养品质的特性。本文综述了导致木薯（Manihot esculenta Crantz）贮藏根特性发生显著变化的变异、进化、遗传资源和驯化相关的中性遗传论题。传统育种通过更新资源信息,包括遗传资源、遗传多样性、基因组学、转录组学、蛋白质组学和代谢的方法改善木薯贮藏根特性,并且介绍了木薯贮藏根淀粉含量、蛋白质含量、类胡萝卜素含量和常规品种的改良。     

大豆氮高效种质苗期筛选与鉴定

氮高效利用种质资源的筛选与鉴定是大豆高产育种的重要前提。本研究以78份大豆种质资源为材料,采用水培养法,分析正常氮（氮浓度为7.5 mmol/L）和低氮（氮浓度为0.75 mmol/L）条件下大豆生物量和耐低氮指数。根据地上部干重、总干重、耐低氮胁迫指数初步筛选出3份耐低氮材料（2011-X-559、2011-X-618、2011-X-639）、3份低氮敏感材料（2011-X-472、2011-X-531、2011-X-547）和2份中间型材料（吉育86、东农53）。进一步复筛测定8份大豆种质材料的叶绿素含量、生物量、氮含量和根系形态构型等17个氮利用相关指标,通过对性状指标的变异系数、相关性和主成分分析,筛选出总干重、整株氮含量、整株总氮、总根长、根体积和根表面积6个指标可作为大豆苗期耐低氮评价关键指标,并依此鉴定出耐低氮材料2011-X-618和低氮敏感材料2011-X-531。本研究为大豆耐低氮机制解析和氮高效育种提供了优异种质资源和理论指导。     

木薯种质资源淀粉特性分析与评价

为了评价和筛选出淀粉品质优良的木薯资源,对212份国内外栽培木薯种质块根淀粉产量性状及淀粉含量、直链淀粉含量、支链淀粉含量、粘度峰值和糊化温度5个重要淀粉特性指标进行研究.结果表明,不同木薯资源各淀粉特性差异较大,不同指标间有一定的相关性,利用概率分级法将8个淀粉产量及特性性状分为5级,即极低、低、中、高和极高,推荐极...     

广西斑茅表型性状遗传多样性分析

为有效评价和利用广西斑茅种质资源,扩增甘蔗遗传基础。对183份广西斑茅种质资源主要表型性状及遗传多样性进行分析。结果表明：广西斑茅种质资源表型遗传多样性比较低,13个描述型性状的遗传多样性指数在0.0000~1.2349之间,平均为0.3070,以毛群较高,生长带形状较低,空心、气根、根点排列和脱叶性4个性状无多态性表现;不同地区的斑茅资源遗传多样性指数在0.2851~0.5072之间,且以钦州的多样性最大,其次是桂林和崇左,以来宾的多样性最小。5个数值型性状的变异系数在13.54%~29.11%之间,平均为19.59%,以叶宽比较大,叶长较小;10个地区的斑茅资源变异系数在16.48%~21.92%之间,以桂林最大,百色最小。通过聚类分析,183份资源可以分为10个类群,各类群遗传分化不明显,与地理来源无密切联系。本研究揭示了广西不同地区斑茅的表型特异性和遗传多样性,为斑茅资源的采集、保育和杂交利用提供理论参考。     

异源染色体附加对普通小麦氮磷吸收能力和利用效率的影响

为明确异源染色体的附加对普通小麦氮、磷吸收能力和利用效率的影响,以中国春为对照,设计不同浓度水平的氮、磷组合进行苗期水培试验,评价了43份中国春背景下小麦异附加系的氮、磷吸收能力和利用效率。对不同水平氮磷组合处理下的苗期表型调查发现,氮、磷胁迫均会抑制地上部分生长,促进地下部分生长;低氮胁迫降低了苗期的株高、茎干重和总干重,提高了根长、叶数、SPAD值及根茎比;磷缺乏提高了根干重和根茎比,抑制了其余性状。在中氮和低氮处理下,Ae.searsii 1SS等13个小麦异附加系的总干重高于中国春,表现出稳定的氮高效;低氮处理下,Ps.huashanica E等9个小麦异附加系的氮吸收能力显著高于中国春,Ps.huashanica C等4个小麦异附加系的氮利用效率显著高于中国春。在磷充足及磷胁迫处理下,Ag.intermedium B等5个小麦异附加系的总干重高于中国春,表现出稳定的磷高效;低磷处理下,Ag.intermedium B等4个小麦异附加系的磷吸收能力显著高于中国春,L.racemosus L附加系和Ag.elongatum 6E附加系的磷利用效率显著高于中国春。进一步分析氮、磷高效的小麦异附加系携带的异源染色体,没有观察到染色体部分同源群聚集的现象。筛选出的异源染色体附加系可作为小麦育种的中间材料,进行养分高效的遗传分析或育种应用。     

Closing the cassava yield gap: An analysis from smallholder farms in East Africa

Cassava yields in Africa are small and it remains unclear which factors most limit yields. Using a series of farm surveys and on-farm and on-station trials in Uganda and western Kenya, we evaluated the importance of abiotic, biotic and associated crop management constraints for cassava production in a range of socio-economic settings as found in smallholder farms in the region. Average yields under farmer management were 8.6 t ha⁻¹, but these were more than doubled to 20.8 t ha⁻¹ by using improved crop establishment, improved genotypes and 100–22–83 kg ha⁻¹ of single-nutrient N–P–K fertilizers. A farm survey revealed large yield differences between farms. Less endowed farmers harvested less cassava per unit area than better endowed farmers (difference of 5.9 and 9.7 t ha⁻¹ in Kenya and Uganda, respectively); differences were associated with less access to labour, poorer soils, and premature harvesting by less endowed farmers. Analysis of 99 on-farm and 6 on-station trials showed that constraints for cassava production varied strongly between sites and years. Poor soil fertility, early water stress and sub-optimal weed management limited cassava production by 6.7, 5.4 and 5.0 t ha⁻¹, respectively, when improved crop establishment and genotypes were used. Pests and diseases were relatively unimportant, while weed management was particularly important in farmer fields during a dry year in Kenya (yield gap of 11.6 t ha⁻¹). The use of complementary analytical tools such as multiple regression and boundary line analysis revealed that many fields were affected by multiple and interacting production constraints. These should be addressed simultaneously if significant productivity improvements are to be achieved. This will be more difficult for less endowed than for better endowed farm households, since the former lack social and financial capital to improve management.     

24份木薯(Manihot esculenta)种质的遗传多样性研究

采用产量性状和12个表型性状聚类分析以及SSR标记技术,对不同产地来源的24份木薯(Manihot esculenta)种质遗传多样性进行了研究。结果表明,依据12个表型性状在欧氏距离系数为39.353处可将供试的24个木薯种质分为3类,一些品种的表型性状与地理来源之间存在相关性;利用18对SSR引物对24份木薯种质进行多态性分析,共检测到154条带,其中多态性带145条,每一个位点上检测到5～12条,平均8.6条。材料间相似系数在0.510～0.967之间,平均相似系数为0.695。以相似系数0.78为结合点,可以将材料分为三大类。不同国家和地区来源的材料不能明显聚类,不同淀粉含量、干物质量分数的品种却聚在一起,且没有发现与淀粉含量、干物质量分数相关的特异性条带。农艺性状的聚类结果与SSR聚类的结果有很大的差异,说明木薯在长期的演化和自然选择过程中发生了显著的表型变化。     

红花种质资源表型多样性分析

以来自国内外的312份红花种质为材料,采用主成分分析与聚类分析,对6个主要表型性状进行多样性分析。结果表明:红花种质资源主要表型性状的遗传变异丰富。顶果球着粒数的多样性指数最高,其次是果球直径;单株种子产量的变异系数最大,其次是单株有效果球数。主成分分析表明,前3个主成分累计贡献率达78.30%,反映了6个性状的大部分信息。基于各种质间6个性状的差异,对312份红花种质进行聚类并划分为7大类群,第Ⅰ类群果球大、顶果球着粒数多,具有增产潜力;第Ⅲ类群综合表现最好,可作为高产育种材料;第Ⅵ类群籽粒大,可作为大粒型选育亲本;其余类群表现一般。该结果可为红花的有效利用及新品种选育提供科学依据。     

干旱条件下不同种茎材料对木薯成活率及产量性状的影响

在干旱条件下,比较4种不同种茎材料对木薯成活率、农艺及产量性状的影响。结果表明：成活率(survival rate,SR)呈现SR1年生种茎(100.0%)＞SR2年生种茎(92.2%)＞SR60 d嫩茎(78.9%)＞SR老茎头(30.0%);鲜薯和薯干产量(root yield,RY)呈现RY1年生种茎＞RY60 d嫩茎＞RY老茎头＞RY2年生种茎;淀粉产量(starch yield,SY)呈现SY60 d嫩茎＞SY1年生种茎＞SY老茎头＞SY2年生种茎;薯干率和鲜薯淀粉含量呈现老茎头＞60 d嫩茎＞2年生种茎＞1年生种茎,且植株密度越小,则薯干率和鲜薯淀粉含量越高。     

Phenotypic Analyses of Multi-Environment Data for Two Diverse Tetraploid Potato Collections: Comparing an Academic Panel with an Industrial Panel

Phenotypic analyses of two different association panels of tetraploid potato cultivars are presented. Association panels are sets of variously related genotypes assembled for association analysis purposes. The aims of this research were to inspect, analyse and compare two phenotypic data sets, a first step in association mapping analysis. A first panel of 205 contemporary and historical cultivars, selected to represent the commercial potato germplasm pool, was evaluated in two trials in 2006, one on sandy soil and the other on clay soil, both with two replications. It was called the academic panel. Data for the second panel with 299 genotypes were compiled from contributions from five breeding companies and included 66 locations and 18 years. Each of the participating breeding companies contributed data from their clonal selection programmes for 38 advanced breeding clones and a series of standard cultivars. It was called the industrial panel. Variance components for genotypic main effects and genotype-by-environment interactions were calculated, and estimates for the random genotypic main effects were produced. The genotypic main effects for 19 agro-morphological and quality traits were used to study trait by trait correlations within each panel. In addition, for the genotypes shared by both panels, the correlation of genetic main effects between the panels was investigated. The heritability of all traits was high and no large differences were observed between panels. Coefficients of trait variation were highly correlated (r = 0.9) for both panels and trait by trait correlations in both panels showed highly similar patterns. These results demonstrate that a single-year balanced field trial as well as using breeders’ records yields robust phenotypic information that can be used in a genome-wide association study. Issues related to data management and definition of traits are discussed.     

非洲香蕉和大蕉产销概况

非洲是全球重要的香蕉和大蕉产出地。2009年非洲香蕉总产约为世界的12.6%;大蕉总产约为世界的81%。两者合计非洲香蕉和大蕉总产约为世界的28%。尤其在非洲撒哈拉边缘,大蕉占了当地大约1亿居民主食的四分之一。非洲香蕉和大蕉主生产区主要分布在非洲东部、西部和中部。东部非洲各国香蕉总产大约为780万t,平均每公顷香蕉产出仅6.7t;大蕉总产大约为1 400万t;香蕉产量上乌干达、卢旺达,坦桑尼亚,肯尼亚分别为前4名;大蕉产量方面,坦桑尼亚,布隆迪、乌干达、肯尼亚分别为前4名。西部非洲各个国家香蕉总产大约为92万t;大蕉总产大约为840万t;香蕉产量上科特迪瓦、几内亚、利比里亚、加纳分别为前4名;大蕉产量方面加纳、尼日利亚、科特迪瓦、几内亚分别为前4名。中部非洲各个国家香蕉总产大约为170万t;平均每公顷单产约7 t;大蕉总产大约为306万t;香蕉产量中安哥拉、喀麦隆、刚果民主共和国、中非分别为前4名;大蕉产量方面喀麦隆、刚果民主共和国、加蓬、中非分别为前4名。尽管非洲是重要的大蕉和香蕉生产区,但只有香蕉被用于出口,目前非洲香蕉出口地主要集中在欧共体市场,占欧共体市场11%的份额,其出口长期由喀麦隆和象牙塔国家垄断,自2006年后加纳开拓了欧盟市场。     

非洲种质在黄淮海的改良与利用研究

对4个非洲种质和4个常用种质组配的16个组合的玉米穗部性状、抗病性及病害与产量的相关性进行分析。结果表明,坦桑尼亚种质ZB903所配制的组合产量表现较稳定,综合抗病性强,在抗病育种中有较大的利用价值;埃塞俄比亚种质与黄改系种质选育的CM07组配的组合产量最高、百粒重大、穗行数多,对产量影响最严重的茎基腐病表现达高抗水平。直接利用非洲种质的效果并不理想,其与黄改系种质杂交选育的自交系可在黄淮海重点利用。瑞德×（塘四平头+非洲种质）是黄淮海利用该种质比较理想的杂种优势模式之一。     

Genetic diversity in blackgram (Vigna mungo L. Hepper)

Blackgram germplasm comprising 484 accessions was evaluated for qualitative and quantitative traits at NARC, Islamabad, Pakistan (33.40°N and 73.07°E). Quantitative traits were analyzed for cluster and principal component analyses. The first four PCs with eigenvalues >1 contributed 79.5% of the variability amongst accessions. Populations with high PC₁ values were high yielding and characterized by low harvest index (HI). The populations with high PC₂ values were late in flowering and maturity but low in HI, grain yield, branches, pods and pods/branch. Nine important characters contributed more positively to the first three PCs. The germplasm was catagorized in five clusters based on average linkage and clusters II, III and IV were more clearly separated than I and V. A selection score (SC) to find appropriate HI range was calculated and high SC was observed for HI range from 30.1 to 35.0% (14.71) and 25.1 to 30.0% (13.84), which is suggested as one of the selection criteria for future blackgram improvement. The germplasm under investigation displayed a wide range of diversity for most of the traits along with some accessions with unique characters which could help to identify landraces with suitable traits to be used in hybridization programme for breeding to broaden genetic base.     

花生属不同区组种质主要植物学性状及分子特性

从主要植物学性状如主茎粗、主茎高、侧枝长、总分枝数、结果分枝数等22个性状和SSR多态性方面对花生属不同区组的19份种质资源的主要特性进行了分析。结果表明，不同种质在形态性状方面存在丰富的变异，匍匐区组的A. rigonii(G2)、花生区组的A. batizocoi（G8）和A. duranensis（G11）在形态方面具有显著区别于其他种质的特点。SSR分析结果也证实，不同野生花生种质具有多样化的分子特征，A. rigonii(G2)、A. batizocoi（G8）和A. duranensis（G11）等在形态方面具有突出特点的种质，能通过很多引物检测出来，形态性状的分析结果与SSR分析结果一致。引物10D4的检测效率很高，能鉴定19份资源中的11份。根据25对SSR引物的扩增结果，绘制了19份资源的指纹图谱。     

Adaptation,diversity, and exploitation of global white lupin (Lupinus albus L.) landrace genetic resources

White lupin requires grain yield improvement to realize its potential as a high-protein grain crop. Some 121 entries representing 13 germplasm pools (11 landrace pools from European countries and from regions of North and East Africa, West Asia and Atlantic islands, and one winter-type and one spring-type variety pools) were evaluated in three major agroclimatic conditions, i.e., Mediterranean and subcontinental climate in Italy under autumn sowing and suboceanic climate in France under spring sowing, with the aim to assess: (i) the variation among and within germplasm pools for grain yield and 13 major morphophysiological traits; (ii) the impact of evaluation environments on entry characteristics; and (iii) the relation of wide- and specific-adaptation responses with morphophysiological traits. Indications on top-yielding genetic resources, entry morphophysiological traits and association of these traits with grain yield were largely environment-specific. Germplasm pools summarized a fairly high portion of genotypic and genotype × environment (GE) interaction variation, indicating their usefulness as a criterion for locating genetic resources with specific characteristics. Adaptive responses of germplasm pools and individual entries, modeled through Additive Main effects and Multiplicative Interaction analysis, highlighted the outstanding agronomic value for specific agroclimatic conditions of a few landrace germplasm pools in comparison with variety pools. Overall within-pool diversity for morphophysiological traits and adaptive response was largest in the landrace pools from Italy, Turkey, East Africa and West Asia. Only flowering time and individual seed weight exhibited high genetic correlations between environments for entry response, suggesting caution in inferring accession characteristics from evaluation data obtained in environments very different from those targeted by possible germplasm users. Optimal flowering time was early in the spring-sown environment, intermediate in the Mediterranean environment, and late (associated with winter survival) in the subcontinental-climate environment. Owing to the association of phenology with several other traits, germplasm ordination for adaptation pattern and for overall morphophysiological variation were very similar. Pod fertility emerged among the seed yield components because of its correlation with grain yield in each environment combined with fairly low GE interaction. Beside contributing to the ecogeographic classification of landrace germplasm, our results can support breeding programs of Europe and Mediterranean-climate regions in defining useful genetic resources, adaptation strategies and adaptive traits. Genetic resources from Madeira & Canaries (high-yielding across environments), Italy (featuring high adaptive and morphophysiological diversity) and a few other regions are of special interest for breeding in targeted definite agroclimatic conditions.     

花生EMS诱变体系的探索及突变体鉴定

突变体创制对花生遗传改良和功能基因组学研究具有重要意义。为获得最佳诱变效果,本研究对不同基因型花生品种的EMS诱变条件进行摸索,发现花育22号、花育71、花育9301、狮头企和伏花生的最适诱变浓度分别为0.4%、0.5%、0.3%、0.5%和0.3%。通过对最适EMS浓度诱变处理下苗期芽长、株高、根长及根数目分析,发现5个品种虽然都能正常成苗,但均受到较严重的损伤。在预实验基础上,用浓度为0.4%的EMS溶液处理了大约5000粒花育22号种子,M1及M2世代性状调查显示突变群体表型丰富,出现株高、株型、荚果、籽仁、分枝数、叶形等表型变异株系,表型变异率为12.9%。本研究为花生遗传改良和功能基因组学研究提供了丰富的种质材料。     

205份玉米种质资源表型性状遗传多样性分析及优异种质筛选

为了拓宽玉米种质资源遗传基础,了解玉米种质资源表型性状遗传多样性水平,选择205份玉米种质资源的23个表型性状,利用变异系数、遗传多样性指数及多种分析方法,结合F值综合评价玉米种质资源。结果表明,大多数种质资源花丝色及花药色均为黄绿色,株型中间型,轴色浅红色,穗型筒形,粒型硬粒型,子粒形状中间形,粒色浅黄。穗长的遗传多样性指数H''最大,穗行数的H''最小;粗蛋白质含量和粗脂肪含量的H''相同,总淀粉含量的H''最小。15个数量性状和3个品质性状之间呈现显著或极显著正相关,千粒重与穗行数呈极显著负相关,各数量性状间相互联系又相互制约。通过聚类分析,205份资源被划分为3大类群。通过综合得分F值筛选出10份优异玉米种质,可作为优良的种质资源创新材料和遗传育种的亲本来源。     

簕杜鹃种质资源表型性状的遗传多样性分析

为深入研究簕杜鹃种质资源的遗传多样性和后期簕杜鹃种质资源的创制与利用提供参考,本研究对国内外收集的100份簕杜鹃种质资源的9个数量性状和19个质量性状进行测定与评价,利用相关性分析、主成分分析和聚类分析等方法,探讨其种质资源表型性状的遗传多样性。结果表明,在测定的19个质量性状中共检测到78个变异类型,28个表型性状的遗传多样性指数在0.61~2.06之间,9个数量性状的变异系数为12.38%~37.68%,以花序梗长度的变异系数最大（37.68%）。相关性分析结果表明性状之间关系复杂,大部分性状之间呈现显著相关性,其中叶片大小与苞片大小呈极显著正相关。通过主成分分析将簕杜鹃28个表型性状转化成9个主成分因子,累计贡献率达到70.42%,其中叶片长度、叶片宽度、苞片长度、苞片宽度、花冠直径、花被管长度、叶节间长度、花被管形状、株型等是造成簕杜鹃种质资源表型性状差异的主要因素。聚类分析可将100份簕杜鹃种质资源分为6类,其中第一类群包含7份簕杜鹃种质资源,该类群品种多为重瓣品种,具有较高的观赏价值,但后期苞片宿存,影响观赏性。第二类包含16份簕杜鹃种质资源,叶片大小中等,形状多为椭圆形,苞片形状以卵形为主。第三类包含10份簕杜鹃品种,该类群簕杜鹃品种苞片先端性状为渐尖,基部形状为心形,叶面多稍微上捧。第四类包含18份材料,该类群品种叶片中等,叶柄较短,苞片形态为阔椭圆形。第五类群包含8份簕杜鹃品种,该类群簕杜鹃品种苞片形状特异,叶柄短小,叶节间短缩,其中“塔类”系列簕杜鹃品种,整体形似宝塔,观赏价值较高。第六类包含41份材料,其中在欧式距离为17时,可将第六类群分为4个亚群,第1亚群仅包含1个品种,第2亚群簕杜鹃品种叶片多含有次色,第3亚群叶片较大,第4亚群叶片主要以卵形为主,叶面光滑无毛,苞片主要以卵形为主,花被管性状以纤细和中部收缩为主。本研究明确了不同簕杜鹃种质资源的农艺性状的特异性和遗传多样性,筛选具有特异性状的簕杜鹃种质资源,为簕杜鹃新品种的选育提供理论基础。     

木薯根尖染色体制片方法的优化

以华南6号木薯根尖为材料,采用酶解去壁低渗法和压片法,制备木薯染色体标本,并对其制片过程中的预处理药品、预处理时间、酶解时间等因子进行优化。结果表明：酶解去壁低渗法能获得较好的染色体标本,α-溴代萘与对二氯苯饱和液的混合液和0．1％的秋水仙素与0.002 mol/L 8-羟基喹啉混合液的预处理效果最好,预处理时间以2 h为宜,酶解时间4 h效果最好。