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1.
Hervé Vanderschuren Isabel Moreno Ravi B. Anjanappa Ima M. Zainuddin Wilhelm Gruissem 《PloS one》2012,7(9)
Cassava brown streak disease (CBSD) and cassava mosaic disease (CMD) are currently two major viral diseases that severely reduce cassava production in large areas of Sub-Saharan Africa. Natural resistance has so far only been reported for CMD in cassava. CBSD is caused by two virus species, Cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus (UCBSV). A sequence of the CBSV coat protein (CP) highly conserved between the two virus species was used to demonstrate that a CBSV-CP hairpin construct sufficed to generate immunity against both viral species in the cassava model cultivar (cv. 60444). Most of the transgenic lines showed high levels of resistance under increasing viral loads using a stringent top-grafting method of inoculation. No viral replication was observed in the resistant transgenic lines and they remained free of typical CBSD root symptoms 7 month post-infection. To generate transgenic cassava lines combining resistance to both CBSD and CMD the hairpin construct was transferred to a CMD-resistant farmer-preferred Nigerian landrace TME 7 (Oko-Iyawo). An adapted protocol allowed the efficient Agrobacterium-based transformation of TME 7 and the regeneration of transgenic lines with high levels of CBSV-CP hairpin-derived small RNAs. All transgenic TME 7 lines were immune to both CBSV and UCBSV infections. Further evaluation of the transgenic TME 7 lines revealed that CBSD resistance was maintained when plants were co-inoculated with East African cassava mosaic virus (EACMV), a geminivirus causing CMD. The innovative combination of natural and engineered virus resistance in farmer-preferred landraces will be particularly important to reducing the increasing impact of cassava viral diseases in Africa. 相似文献
2.
Simple sequence repeat marker diversity in cassava landraces: genetic diversity and differentiation in an asexually propagated crop 总被引:7,自引:0,他引:7
Fregene MA Suarez M Mkumbira J Kulembeka H Ndedya E Kulaya A Mitchel S Gullberg U Rosling H Dixon AG Dean R Kresovich S 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2003,107(6):1083-1093
Cassava (Manihot esculenta) is an allogamous, vegetatively propagated, Neotropical crop that is also widely grown in tropical Africa and Southeast Asia. To elucidate genetic diversity and differentiation in the crop's primary and secondary centers of diversity, and the forces shaping them, SSR marker variation was assessed at 67 loci in 283 accessions of cassava landraces from Africa (Tanzania and Nigeria) and the Neotropics (Brazil, Colombia, Peru, Venezuela, Guatemala, Mexico and Argentina). Average gene diversity (i.e., genetic diversity) was high in all countries, with an average heterozygosity of 0.5358 ± 0.1184. Although the highest was found in Brazilian and Colombian accessions, genetic diversity in Neotropical and African materials is comparable. Despite the low level of differentiation [Fst(theta) = 0.091 ± 0.005] found among country samples, sufficient genetic distance (1-proportion of shared alleles) existed between individual genotypes to separate African from Neotropical accessions and to reveal a more pronounced substructure in the African landraces. Forces shaping differences in allele frequency at SSR loci and possibly counterbalancing successive founder effects involve probably spontaneous recombination, as assessed by parent-offspring relationships, and farmer-selection for adaptation.Communicated by H.C. Becker 相似文献
3.
Anderson JV Delseny M Fregene MA Jorge V Mba C Lopez C Restrepo S Soto M Piegu B Verdier V Cooke R Tohme J Horvath DP 《Plant molecular biology》2004,56(4):527-539
Cassava (Manihot esculenta) is a major food staple for nearly 600 million people in Africa, Asia, and Latin America. Major losses in yield result from biotic and abiotic stresses that include diseases such as Cassava Mosaic Disease (CMD) and Cassava Bacterial Blight (CBB), drought, and acid soils. Additional losses also occur from deterioration during the post-harvest storage of roots. To help cassava breeders overcome these obstacles, the scientific community has turned to modern genomics approaches to identify key genetic characteristics associated with resistance to these yield-limiting factors. One approach for developing a genomics program requires the development of ESTs (expressed sequence tags). To date, nearly 23000 ESTs have been developed from various cassava tissues, and genotypes. Preliminary analysis indicates existing EST resources contain at least 6000–7000 unigenes. Data presented in this report indicate that the cassava ESTs will be a valuable resource for the study of genetic diversity, stress resistance, and growth and development, not only in cassava, but also other members of the Euphorbiaceae family. 相似文献
4.
Thomas C. de Bang Adebola A. Raji Ivan L. Ingelbrecht 《Plant Molecular Biology Reporter》2011,29(3):655-662
Current methods for molecular fingerprinting of cassava (Manihot esculenta Crantz) have limited throughput or are costly, thus preventing the characterization of large germplasm collections such as
those held by the International Agricultural Research Centers or National Research Institutions, which comprise hundreds to
thousands of accessions. Here, we report the development of a fluorescence-based multiplex simple sequence repeat (SSR) marker
kit that enables accurate and cost-effective cassava fingerprinting. The kit comprises 16 SSR markers assembled into five
multiplex panels and was tested on 21 cassava cultivars alongside one accession of Manihot epruinosa, a wild relative. A total of 68 alleles were detected with, on average, 4.25 alleles per locus and a polymorphism information
content of 0.53. The marker kit reported here is comparable to previously published amplified fragment length polymorphism
and SSR marker systems in terms of discriminating power and informativeness while offering significant advantages in speed
and cost of marker analysis. Previous molecular genetic diversity studies have suggested that cassava germplasm collections
contain duplicate entries based on the occurrence of identical genetic profiles. Using the newly developed microsatellite
kit, three out of six putative duplicate accessions could be readily differentiated, showing that these are distinct genotypes.
The relevance of these findings with respect to the characterization and management of large cassava germplasm collections
is discussed. 相似文献
5.
6.
Loss of CMD2‐mediated resistance to cassava mosaic disease in plants regenerated through somatic embryogenesis
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Getu Beyene Raj Deepika Chauhan Henry Wagaba Theodore Moll Titus Alicai Douglas Miano James C. Carrington Nigel J. Taylor 《Molecular Plant Pathology》2016,17(7):1095-1110
Cassava mosaic disease (CMD) and cassava brown streak disease (CBSD) are the two most important viral diseases affecting cassava production in Africa. Three sources of resistance are employed to combat CMD: polygenic recessive resistance, termed CMD1, the dominant monogenic type, named CMD2, and the recently characterized CMD3. The farmer‐preferred cultivar TME 204 carries inherent resistance to CMD mediated by CMD2, but is highly susceptible to CBSD. Selected plants of TME 204 produced for RNA interference (RNAi)‐mediated resistance to CBSD were regenerated via somatic embryogenesis and tested in confined field trials in East Africa. Although micropropagated, wild‐type TME 204 plants exhibited the expected levels of resistance, all plants regenerated via somatic embryogenesis were found to be highly susceptible to CMD. Glasshouse studies using infectious clones of East African cassava mosaic virus conclusively demonstrated that the process of somatic embryogenesis used to regenerate cassava caused the resulting plants to become susceptible to CMD. This phenomenon could be replicated in the two additional CMD2‐type varieties TME 3 and TME 7, but the CMD1‐type cultivar TMS 30572 and the CMD3‐type cultivar TMS 98/0505 maintained resistance to CMD after passage through somatic embryogenesis. Data are presented to define the specific tissue culture step at which the loss of CMD resistance occurs and to show that the loss of CMD2‐mediated resistance is maintained across vegetative generations. These findings reveal new aspects of the widely used technique of somatic embryogenesis, and the stability of field‐level resistance in CMD2‐type cultivars presently grown by farmers in East Africa, where CMD pressure is high. 相似文献
7.
E. A. Masumba F. Kapinga G. Mkamilo K. Salum H. Kulembeka S. Rounsley J. V. Bredeson J. B. Lyons D. S. Rokhsar E. Kanju M. S. Katari A. A. Myburg N. A. van der Merwe M. E. Ferguson 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2017,130(10):2069-2090
Key message
QTL consistent across seasons were detected for resistance to cassava brown streak disease induced root necrosis and foliar symptoms. The CMD2 locus was detected in an East African landrace, and comprised two QTL.Abstract
Cassava production in Africa is compromised by cassava brown streak disease (CBSD) and cassava mosaic disease (CMD). To reduce costs and increase the precision of resistance breeding, a QTL study was conducted to identify molecular markers linked to resistance against these diseases. A bi-parental F1 mapping population was developed from a cross between the Tanzanian farmer varieties, Namikonga and Albert. A one-step genetic linkage map comprising 943 SNP markers and 18 linkage groups spanning 1776.2 cM was generated. Phenotypic data from 240 F1 progeny were obtained from two disease hotspots in Tanzania, over two successive seasons, 2013 and 2014. Two consistent QTLs linked to resistance to CBSD-induced root necrosis were identified in Namikonga on chromosomes II (qCBSDRNFc2Nm) and XI (qCBSDRNc11Nm) and a putative QTL on chromosome XVIII (qCBSDRNc18Nm). qCBSDRNFc2Nm was identified at Naliendele in both seasons. The same QTL was also associated with CBSD foliar resistance. qCBSDRNc11Nm was identified at Chambezi in both seasons, and was characterized by three peaks, spanning a distance of 253 kb. Twenty-seven genes were identified within this region including two LRR proteins and a signal recognition particle. In addition, two highly significant CMD resistance QTL (qCMDc12.1A and qCMDc12.2A) were detected in Albert, on chromosome 12. Both qCMDc12.1A and qCMDc12.2A lay within the range of markers reported earlier, defining the CMD2 locus. This is the first time that two loci have been identified within the CMD2 QTL, and in germplasm of apparent East African origin. Additional QTLs with minor effects on CBSD and CMD resistance were also identified.8.
9.
Patroba Odeny Ojola Evans N. Nyaboga Paul N. Njiru George Orinda 《Journal of Genetic Engineering and Biotechnology》2018,16(1):125-131
Cassava (Manihot esculenta Crantz) is the most important staple food for more than 300?million people in Africa, and anthracnose disease caused by Colletotrichum gloeosporioides f. sp. manihotis is the most destructive fungal disease affecting cassava production in sub-Saharan Africa. The main objective of this study was to improve anthracnose resistance in cassava through genetic engineering. Transgenic cassava plants harbouring rice thaumatin-like protein (Ostlp) gene, driven by the constitutive CaMV35S promoter, were generated using Agrobacterium-mediated transformation of friable embryogenic calli (FEC) of cultivar TMS 60444. Molecular analysis confirmed the presence, integration, copy number of the transgene all the independent transgenic events. Semi-quantitative RT-PCR confirmed high expression levels of Ostlp in six transgenic lines tested. The antifungal activity of the transgene against Colletotrichum gloeosporioides pathogen was evaluated using the leaves and stem cuttings bioassay. The results demonstrated significantly delayed disease development and reduced size of necrotic lesions in leaves and stem cuttings of all transgenic lines compared to the leaves and stem cuttingss of non-transgenic control plants. Therefore, constitutive overexpression of rice thaumatin-like protein in transgenic cassava confers enhanced tolerance to the fungal pathogen C. gloeosporioides f. sp. manihotis. These results can therefore serve as an initial step towards genetic engineering of farmer-preffered cassava cultivars for resistance to anthracnose disease. 相似文献
10.
Identification and mapping of molecular markers linked to rust resistance genes located on chromosome 1RS of rye using wheat-rye translocation lines 总被引:13,自引:0,他引:13
Mago R Spielmeyer W Lawrence J Lagudah S Ellis G Pryor A 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2002,104(8):1317-1324
The short arm of rye (Secale cereale) chromosome 1 has been widely used in breeding programs to incorporate new disease resistance genes into wheat. Using wheat-rye translocation and recombinant lines, molecular markers were isolated and mapped within chromosomal regions of 1RS carrying rust resistance genes Lr26, Sr31, Yr9 from 'Petkus' and SrR from 'Imperial' rye. RFLP markers previously mapped to chromosome 1HS of barley - flanking the complex Mla powdery mildew resistance gene locus - and chromosome 1DS of Aegilops tauschii - flanking the Sr33 stem rust resistance gene - were shown to map on either side of rust resistance genes on 1RS. Three non cross-hybridising Resistance Gene Analog markers, one of them being derived from the Mla gene family, were mapped within same region of 1RS. PCR-based markers were developed which were tightly linked to the rust resistance genes in 'Imperial' and 'Petkus' rye and which have potential for use in marker-assisted breeding. 相似文献
11.
Cassava mosaic disease (CMD) caused by cassava mosaic geminiviruses (CMGs) is one of the most devastating crop diseases and a major constraint for cassava cultivation. CMD has been reported only from the African continent and Indian subcontinent despite the large-scale cultivation of cassava in Latin America and several South-East Asian countries. Seven CMG species have been reported from Africa and two from the Indian subcontinent and, in addition, several strains have been recognized. Recombination and pseudo-recombination between CMGs give rise not only to different strains, but also to members of novel virus species with increased virulence and a new source of biodiversity, causing severe disease epidemics. CMGs are known to trigger gene silencing in plants and, in order to counteract this natural host defence, geminiviruses have evolved suppressor proteins. Temperature and other environmental factors can affect silencing and suppression, and thus modulate the symptoms. In the case of mixed infections of two or more CMGs, there is a possibility for a synergistic interaction as a result of the presence of differential and combinatorial suppressor proteins. In this article, we provide the status of recent research findings with regard to the CMD complex, present the molecular biology knowledge of CMGs with reference to other geminiviruses, and highlight the mechanisms by which CMGs have exploited nature to their advantage. 相似文献
12.
13.
Cassava genetic transformation and its application in breeding 总被引:1,自引:0,他引:1
As a major source of food, cassava (Manihot esculenta Crantz) is an important root crop in the tropics and subtropics of Africa and Latin America, and serves as raw material for the production of starches and bioethanol in tropical Asia. Cassava improvement through genetic engineering not only overcomes the high heterozygosity and serious trait separation that occurs in its traditional breeding, but also quickly achieves improved target traits. Since the first report on genetic transformation in cassava in 1996, the technology has gradually matured over almost 15 years of development and has overcome cassava genotype constraints, changing from mode cultivars to farmer-preferred ones. Significant progress has been made in terms of an increased resistance to pests and diseases, biofortification, and improved starch quality, building on the fundamental knowledge and technologies related to planting, nutrition, and the processing of this important food crop that has often been neglected. Therefore, cassava has great potential in food security and bioenergy development worldwide. 相似文献
14.
Cassava (Manihot esculenta) is an economically important crop that is grown in tropical and sub-tropical regions. Use of molecular technology for genetic
improvement of cassava has been limited by the lack of a large set of DNA markers and a genetic map. Therefore, the aims here
were to develop additional simple sequence repeat (SSR) markers from the public expressed sequence tags (ESTs), and to construct
a genetic linkage map. In this study, we designed 425 EST-SSR markers from sequences obtained from the cassava EST database
in GenBank, and integrated them with 667 SSR markers from a microsatellite-enriched genomic sequence received from the International
Center for Tropical Agriculture (CIAT). Of these, 107 EST-SSR and 500 genomic SSR primer pairs showed polymorphic patterns
when screened in two cassava varieties, Hauy Bong 60 and Hanatee, which were used as female and male parental lines, respectively.
Within the 107 and 500 primer pairs, 81 and 226 EST-SSR and SSR primer pairs were successfully genotyped with 100 samples
of F1 progeny, respectively. The results showed 20 linkage groups consisting of 211 markers—56 EST-SSR and 155 SSR markers—spanning
1,178 cM, with an average distance between markers of 5.6 cM and about 11 markers per linkage group. These novel EST-SSR markers
provided genic PCR-based co-dominant markers that were useful, reliable and economical. The EST-SSRs were used together with
SSR markers to construct the cassava genetic linkage map which will be useful for the identification of quantitative trait
loci controlling the traits of interest in cassava breeding programs. 相似文献
15.
Uwe Sonnewald Alisdair R. Fernie Wilhelm Gruissem Pascal Schlpfer Ravi B. Anjanappa Shu‐Heng Chang Frank Ludewig Uwe Rascher Onno Muller Anna M. van Doorn Ismail Y. Rabbi Wolfgang Zierer 《The Plant journal : for cell and molecular biology》2020,103(5):1655-1665
Cassava (Manihot esculenta Crantz) is one of the important staple foods in Sub‐Saharan Africa. It produces starchy storage roots that provide food and income for several hundred million people, mainly in tropical agriculture zones. Increasing cassava storage root and starch yield is one of the major breeding targets with respect to securing the future food supply for the growing population of Sub‐Saharan Africa. The Cassava Source–Sink (CASS) project aims to increase cassava storage root and starch yield by strategically integrating approaches from different disciplines. We present our perspective and progress on cassava as an applied research organism and provide insight into the CASS strategy, which can serve as a blueprint for the improvement of other root and tuber crops. Extensive profiling of different field‐grown cassava genotypes generates information for leaf, phloem, and root metabolic and physiological processes that are relevant for biotechnological improvements. A multi‐national pipeline for genetic engineering of cassava plants covers all steps from gene discovery, cloning, transformation, molecular and biochemical characterization, confined field trials, and phenotyping of the seasonal dynamics of shoot traits under field conditions. Together, the CASS project generates comprehensive data to facilitate conventional breeding strategies for high‐yielding cassava genotypes. It also builds the foundation for genome‐scale metabolic modelling aiming to predict targets and bottlenecks in metabolic pathways. This information is used to engineer cassava genotypes with improved source–sink relations and increased yield potential. 相似文献
16.
Abundance,diversity and geographic distribution of cassava mosaic disease pandemic‐associated Bemisia tabaci in Tanzania
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L. S. Tajebe S. B. Boni D. Guastella V. Cavalieri O. S. Lund C. P. Rugumamu C. Rapisarda J. P. Legg 《Journal of Applied Entomology》2015,139(8):627-637
Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae), one of the most economically important agricultural pests worldwide, is the vector of cassava mosaic geminiviruses that cause cassava mosaic disease (CMD). In East and Central Africa, a severe CMD pandemic that spread from Uganda in the late 1980s still continues to devastate cassava crops. To assess the association of distinct B. tabaci genetic groups with the CMD pandemic, mitochondrial cytochrome oxidase I gene sequences were analysed from whiteflies collected during surveys conducted from 2010 to 2013 in Tanzania. Four genetic groups – Sub‐Saharan Africa 1 (SSA1), Mediterranean, Indian Ocean and East Africa 1, and a group of unknown whitefly species were identified. SSA1 comprised four subgroups: SSA1‐SG1, SSA1‐SG2, SSA1‐SG1/2 and SSA1‐SG3. SSA1‐SG1 was confined to the pandemic‐affected north‐western parts of Tanzania whilst SSA1‐SG2 and SSA1‐SG3 were found in the central and eastern parts not yet affected by the pandemic. The CMD pandemic front was estimated to lie in Geita Region, north‐western Tanzania, and to be spreading south‐east at a rate of ca 26 km/year. The pandemic‐associated B. tabaci SSA1‐SG1 predominated up to 180 km ahead of the CMD front indicating that changes in whitefly population characteristics precede changes in disease characteristics. 相似文献
17.
P. Sseruwagi M.N. Maruthi J. Colvin M.E.C. Rey J.K. Brown & J.P. Legg 《Entomologia Experimentalis et Applicata》2006,119(2):145-153
Bemisia tabaci (Genn.) (Homoptera: Aleyrodidae) is the vector of cassava mosaic geminiviruses (CMGs), which are the main production constraint to cassava [Manihot esculenta Crantz (Euphorbiaceae)], both in Uganda and elsewhere in Africa. Two B. tabaci genotype clusters, Ug1 and Ug2, differentiated at 8% nucleotide (nt) divergence within the mitochondrial cytochrome oxidase I (mtCOI) gene, have been shown to occur on cassava in Uganda. However, the role of alternative hosts in the ecology of cassava B. tabaci genotypes and their possible involvement in the epidemiology of cassava mosaic disease (CMD) in Uganda remain unknown. In this study, we investigated the restriction of cassava B. tabaci genotypes to cassava and the colonization of alternative host species in select cassava‐growing areas of the country in 2003 and 2004. Bemisia tabaci adults and 4th instar nymphs were collected from cassava and 11 other cultivated and uncultivated species occurring adjacent to the sampled cassava fields. Phylogenetic analysis of mtCOI sequences revealed that only a single genotype cluster, Ug1, was present on both cassava and non‐cassava plant species sampled in this study. The Ug1 genotypes (n = 49) shared 97–99% nt identity with the previously described cassava‐associated B. tabaci populations in southern Africa, and were ~8% and ~13% divergent from Ug2 and the ‘Ivory Coast cassava’ genotypes in Uganda and Ivory Coast, respectively. The Ug1 genotypes occurred (as adults) on all 12 source‐plant species sampled. However, based on the presence of B. tabaci 4th instar nymphs, the Ug1 genotypes (n = 13) colonized cassava and five other non‐cassava plant species: Manihot glaziovii, Jatropha gossypifolia, Euphorbia heterophylla, Aspilia africana, and Abelmoschus esculentus, suggesting that cassava B. tabaci (Ug1 genotypes) are not restricted to cassava in Uganda. No Ug2‐like genotypes were detected on any of the plant species sampled, including cassava, in this study. The identification of additional hosts for at least one genotype cluster, Ug1, known also to colonize cassava, and which was hitherto thought to be ‘cassava‐restricted’ may have important epidemiological significance for the spread of CMGs in Uganda. 相似文献
18.
Many in situ conservation programs have been developed to preserve plant landrace diversity and to promote its sustainable utilization, but little is known about the effectiveness of the developed programs in conserving plant genetic diversity. We investigated the effectiveness of an unregulated (i.e., unplanned or open) conservation system maintained by Thai farmers in conserving Thai elite cassava (Manihot esculenta Crantz) varieties. Specifically, we compared genetic diversity of 266 cassava clones that were collected from 80 farms in eight provinces with 16 cassava landraces and varieties released since the 1970s through genotyping with 35 informative simple sequence repeat (SSR) markers. The SSR analysis revealed a large regional heterogeneity in cassava diversity, with a strong genetic differentiation of the assayed clones among the 80 farms (19.8 %) and across the eight provinces (11.8 %). Significant associations were also found between SSR variation and farm agro-ecological factors or some farming practices. However, there was no significant genetic differentiation (0.9 %) between the 266 farm clones and 16 reference varieties. These findings suggest that the Thai elite cassava genetic diversity was fortuitously conserved by the farmers through farming with different sets of varieties. Implications of these findings are discussed with respect to on-farm conservation of plant genetic resources. 相似文献
19.
20.
V. Jorge M. Fregene C. M. Vélez M. C. Duque J. Tohme V. Verdier 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2001,102(4):564-571
We evaluated cassava bacterial blight (CBB) infection in an pair-cross population of 150 individuals derived from an intra-specific
cross between two non-inbred cassava (Manihot esculenta Crantz) lines. The replicated trials were carried out in the field under high disease pressure over two consecutive crop
cycles. Evaluations were conducted at 4 and 7 months after planting for the two cycles. Simple regression analysis and the
nonparametric Kruskal-Wallis rank-sum test revealed that eight quantitative trait loci (QTLs) were involved in resistance.
We detected changes in QTLs from crop cycle to crop cycle. The pathogen population (Xanthomonas axonopodis pv. manihotis) was also monitored over the period, using a restriction fragment length polymorphism probe and pathogenic tests. Changes
in QTL detection over the 2 years could be correlated with changes in pathogen population structure. One QTL, located in linkage
group D, was conserved over the two crop cycles, and in field to greenhouse evaluations. This study thus identified molecular
markers useful for marker assisted-selection, a technique that can accelerate the long, multiple-season process of breeding
for CBB resistance.
Received: 1 January 2000 / Accepted: 25 June 2000 相似文献