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1.
Breeding cassava for resistance to cassava mosaic disease 总被引：4，自引：0，他引：4
Summary Cassava mosaic disease (CMD) is one of the most serious and widespread diseases throughout cassava growing areas in Africa, causing yield reductions of up to 90%. Early research on breeding of cassava (Manihot esculenta
Crantz) for resistance to CMD in Africa is reviewed. Changes in population size and in activity of the white-fly vector to CMD (Bemisia tabaci
Genn.) in relation to changes in environmental conditions such as amount and distribution of rainfall, light intensity and temperature are discussed in relation to screening for resistance to CMD. Over the past eight years, significant progress has been made at the International Institute of Tropical Agriculture (IITA). Resistance to CMD has been successfully incorporated into high yielding cultivars of acceptable quality. The CMD resistant material has been evaluated and many promising clones have been selected in various countries in tropical Africa and India. The resistance has been effective in those countries. 相似文献
2.
Joseph Akwasi Manu-Aduening Bright Boakye Peprah Adelaide Agyeman 《Journal of Crop Science and Biotechnology》2013,16(1):23-28
Availability of genetic diversity is important in selecting suitable cultivars for crop improvement. Progenies of crosses between 19 farmer-preferred cassava landraces and Cassava Mosaic Disease (CMD)-resistant cultivar TME 11 were evaluated and compared with their maternal parents to assess their genetic variability and genetic gains based on CMD tolerance, some growth variables and root yield. The combined analysis of variance for the traits showed significant genotypic differences amongst the progenies and the parents. Apart from a few instances, the differences in replications and years were also significant. Genetic variability components showed high heritability ranging from 92.3 to 99.6% and moderately high genetic gains of 54.1 to 99.6% for the parental cultivars. Apart from canopy spread and plant height, heritability and genetic gains of the progenies were slightly lower than the parents indicating high variability within families of the progenies. The phenotypic coefficient of variation was slightly greater than genotypic coefficient of variation indicating minimal influence of environment on the genotypes. For most of the characters evaluated, the mean performance of the progenies was higher than their corresponding parental lines. Although the genotypes differed significantly (P < 0.001) for all traits evaluated, cultivars such as Afebankye, Bosome nsia, Cedi bankye, 262 Debor, Kwadaso 25, Nkaakom 57 and Sisipe were found to constitute a pool of germplasm with adequate variability. The negative correlation between CMD incidence and other traits evaluated showed significant progress made in the breeding program. 相似文献
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为了对巴西木薯种质资源进行遗传多样性、亲缘关系和群体遗传结构分析,本研究利用了7946个SNPs和1997个InDels分子标记,通过ADMIXTURE软件进行群体结构分析、GCTA软件进行主成分分析。结果显示,巴西木薯被划分为9个亚群。这与利用PHYLIP进行的聚类分析结果大概一致,其中亚群1、亚群2、亚群4、亚群6和亚群8能较好地分别聚在一起,而其他亚群中的样品大致能聚在一起,且样品间有一定的交叉。巴西木薯种质资源遗传多样性指数(0.274)高于中国、尼日利亚等,其中巴西木薯亚群5具有相对较高的遗传多样性水平(0.29)。巴西木薯各亚群的群体遗传分化程度较低(群体分化指数在0.03~0.15之间),但高于中国木薯种质资源的群体分化指数。各木薯材料间的遗传距离变幅为0.084~0.297,平均遗传距离为0.228。本研究结果可为后续关联分析发掘优良等位基因及引种提供依据。 相似文献
5.
SUN Qian ZOU Mei-Ling ZHANG Chen-Ji JIANG Si-Rong Eder Jorge de Oliveira ZHANG Sheng-Kui XIA Zhi-Qiang WANG Wen-Quan LI You-Zhi 《作物学报》1962,47(1):42-49
As a typical tropical crop, cassava (Manihot esculenta Crantz) has the characteristics of drought resistance, barren resistance, high biomass and so on. In addition to being used for food and forage, it can also be used for production, processing and starch extraction. Due to highly heterozygous cassava genome, breeding is more difficult. Enriching the genetic diversity of cassava germplasm, comprehensively evaluating its genetic background and traits, and discovering superior alleles that control excellent traits are of great significance for cassava breeding in the future. In order to analyze the genetic diversity, genetic relationship and population structure of cassava germplasm in Brazil, 7946 SNPs and 1997 InDels molecular markers were used. Population structure analysis was performed by ADMIXTURE software, and principal component analysis was performed by GCTA software. Brazilian cassava was divided into nine subgroups, and was roughly consistent with the results of cluster analysis using PHYLIP. Among them, subgroup 1, subgroup 2, subgroup 4, subgroup 6, and subgroup 8 could be clustered together respectively, while the samples of other subgroups could be roughly clustered, and there was a certain cross between the samples. The genetic diversity of cassava germplasm in Brazil (0.274) was higher than the genetic diversity level of cassava germplasm in China and Nigeria. Subgroup 5 of Brazil cassava had a relatively high genetic diversity (0.29). The genetic differentiation of subgroups was low (the genetic differentiation vary from 0.03 to 0.15), but higher than domestic cassava germplasm. The genetic distance between cassava accessions varied from 0.084 to 0.297, with the average of 0.228. The results of this study can provide a basis for subsequent association analysis to identify great alleles and introduction. 相似文献
6.
Jonathan Mkumbira Linley Chiwona-Karltun Ulf Lagercrantz Nzola Meso Mahungu John Saka Albert Mhone Mpoko Bokanga Leon Brimer Urban Gullberg Hans Rosling 《Euphytica》2003,132(1):7-22
Cassava roots, a major food in Africa, contain cyanogenic glucosides that may cause toxic effects. Malawian women farmers
considered fields of seemingly similar cassava plants to be mixes of both ‘cool’ and ‘bitter’ cultivars. They regard roots
from ‘cool’ cultivars as non-toxic. Roots of ‘bitter’ were considered to require extensive traditional processing done by
women to be safe for consumption. But curiously, these women farmers preferred ‘bitter’ cultivars since toxicity confers protection
against theft, which was a serious threat to the food security of their families. We studied how well these farmers comprehend
the effects of genetic variations in cassava when dealing with cyanogenesis in this complex system. Using molecular markers
we show that most plants farmers identified as belonging to a particular named cultivar had a genotype typical of that cultivar.
Farmers' ethno-classification into ‘cool’ and ‘bitter’ cultivars corresponded to a genetic sub-division of the typical genotypes
of the most common cultivars, with four-fold higher cyanogenic glucoside levels in the bitter cultivars. Examining morphology,
farmers distinguished genotypes better than did the investigators when using a standard botanical key. Undoubtedly, these
women farmers grasp sufficiently the genetic diversity of cassava with regard to cyanogenesis to simultaneously benefit from
it and avoid its dangers. Consequently, acyanogenic cassava – the breeding of which is an announced good of some cassava genetic
improvement programmes – is not a priority to these farmers. Advances in molecular genetics can help improve food supply in
Africa by rapid micropropagation, marker assisted breeding and introduction of transgenic varieties, but can also help to
elucidate tropical small-scale farmers' needs and skills.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
7.
Summary The two most serious diseases of cassava (Manihot esculenta
Crantz) are cassava mosaic disease (CMD) and cassava bacterial blight (CBB) (Xanthomonas manihotis
Starr). Clone 58308, derived from the third backcross of the interspecific cross of cassava (M. esculenta) x ceara rubber (M. glaziovii), showed a high level of resistance to both diseases. Crosses of 58308 with several other clones which varied from susceptible to moderately susceptible to both diseases gave progenies with a significant genotypic correlation between resistance to both diseases (r=0.90), apparently due to linkage. The heritabilities of resistance to the diseases were estimated at 50–70% for CMD and 25–65% for CBB. Resistance to both diseases is assumed to be polygenic. The correlated response to selection for CMD and for CBB was estimated. 相似文献
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木薯(ManihotesculentaCrantz)在热带亚热带地区有重要的食用价值、生物能源价值、遗传价值和生态价值,深受国内外学者重视。近年来木薯被用于生产燃料乙醇,逐渐成为一种重要的生物能源,木薯的需求量与日俱增。但是生产实践表明,限制木薯生产的主要因素是栽培品种抗寒性低。发掘木薯抗寒相关性状基因,选育抗寒的种质资源,是提高木薯抗寒性的重要途径。为了对木薯抗寒性开展更加全面的研究,归纳了国内外木薯抗寒性及相关性状基因定位的研究进展,探索木薯抗寒基因相关性状的遗传规律,同时结合中国的情况,提出今后研究的方向,为今后木薯抗寒研究提供依据。 相似文献
10.
The virological situation of cassava in Africa is increasing in complexity due to the number and types of viruses isolated
from different locations within the continent. Here, we report the complete nucleotide sequences of both A and B components
of two geminivirus species infecting cassava in the Ivory Coast and review the current knowledge of the molecular and biological
diversity of the African cassava geminiviruses. As a whole, newly obtained sequences are compared with those of the African
cassava mosaic geminiviruses identified to date. Results indicate that all isolates of African cassava mosaic virus (ACMV), irrespective of their geographical origin are clustered together with little or no variation in their genomic sequence.
On the contrary, the genomes of the East African cassava mosaic virus (EACMV) are more genetically diverse due to the frequent occurrence of recombinations within their two components. Indeed,
the EACMV-like viruses vary so much that their classification is becoming problematic. In addition, there is also a large
range of phenotypic symptom variation for each of these virus species, irrespective of the location of isolation. Furthermore,
it has been shown that ACMV and EACMV can be synergistic in cassava, resulting in a greater DNA accumulation and consequently
inducing severe symptoms. For all these reasons, this paper initiates a discussion concerning the species demarcation for
cassava geminivirus.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
11.
Cassava mosaic disease (CMD) caused by a group of begomoviruses and transmitted by whitefly vector is a serious disease in all the cassava-growing areas of Africa. Field evaluation with replication was conducted in 2003 and 2004 in three agroecologies in Nigeria to study the response of 40 cassava genotypes to CMD and to investigate genotype × environment (GE) interactions on their reactions to CMD, using the rank-sum classification and site regression analysis model. The 40 genotypes were separated into resistant (n = 17), moderately resistant (n = 6), moderately susceptible (n = 2) and susceptible (n = 15) groups. Environments, genotypes and GE interactions were all highly significant (P < 0.0001) for the virus disease contributing 9.5%, 71.36% and 19.14%, respectively to total variation. More than 40% of the genotypes were identified as resistant to the disease. Genotypes TMS 98/0581, TMS 99/3073, TMS 97/4763, TMS M98/0040, TMS 98/0505, TMS 97/0211, TMS 97/4769, TMS 99/2123, TMS M98/0068 and TMS 97/0162 were shown to have high resistance to CMD. The study also identified Umudike, in south-east Nigeria, as having high disease severity and the most appropriate site for CMD resistance screening of genotypes. Most of the genotypes exhibited stable resistance to CMD. The implication that the availability of these resistant genotypes as identified in this study could be a source of CMD resistance for further breeding is discussed. 相似文献
12.
Crossing patterns were investigated in an experimental garden of ethnovarieties ofManihot esculenta (Euphorbiaceae) inPiracicaba, São Paulo, Brazil. A model of evolutionary dynamics for cassava presupposes genetic recombination by means of crossing within cassava gardens as a source that amplifies genetic diversity. Quantitative analysis of mating system parameters was performed using progeny arrays assayed for eight allozyme markers. The multilocus outcrossing rate (t m)estimate (0.915±0.04)revealed that outcrossing was prevalent, but that a low level of self-pollination also occurred. The multilocus outcrossing rate ranged from 0.69 to 1.00 among eight varieties. The high value found for the outcrossing rate indicates that the ethnovarieties studied are preferentially allogamous. Genetic recombination occurred through crossing within the cassava garden, in agreement with an assumption of the model of evolutionary dynamics for this species. 相似文献
13.
Marianne Elias Doyle McKey Olivier Panaud Marie Charlotte Anstett Thierry Robert 《Euphytica》2001,120(1):143-157
In this paper we present original data on morphological and genetic diversity of cassava managed by the Makushi Amerindians
from Guyana. Although they propagate cassava exclusively vegetatively by means of stem cuttings, many Amerindian farmers also
use and multiply volunteer plants grown from seeds produced by sexual reproduction. Morphological characters were recorded
for 29 varieties cultivated by the Makushi and two populations of plants originating from volunteer cassava seedlings. Genetic
characterisation with AFLP markers was available for 21 of the examined varieties. The morphological and agronomic characters
were highly variable among varieties. Every variety could be differentiated from any other one, except for one pair of varieties.
However, high intra-varietal variability existed, which might lead to confusions between phenotypically similar varieties
by the Makushi. Seedlings were on average different from the pool of the varieties studied, but 67% were found to resemble
closely enough one of the varieties to be liable to be assigned to it. Confusion between very similar varieties, as well as
assignment of seedlings to a variety, should generate genetic variability within varieties, which was detected with AFLP markers.
As in other sites in Amazonia, there was only a weak correlation between inter-varietal distances assessed with molecular
and with morphological markers, suggesting that diversification of morphological characters has taken place repeatedly and
independently across the Amazonian range of the crop. Diversifying selection, exchanges of varieties between farmers, and
incorporation of sexually produced volunteer plants are key mechanisms responsible for the high diversity observed. Strategies
of conservation of genetic resources should take these dynamic processes into account.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
14.
The propagation of cassava through true seeds (sexual seeds) rather than by clones is a promising option due to its manifold advantages such as enhancing the multiplication rate, keeping the dreaded cassava mosaic disease (CMD) under check, longer seed viability, ease of storage and transport. The high genetic heterogeneity and consequent variation among seedlings is the major stumbling block in sexual propagation. In the present study, a CMD resistant exotic accession MNga-1 and a promising cultivar Ambakadan with profuse fruit setting, seed output and male sterility were identified to be promising parents for the TCS programme. The rate of sexual propagation could be more than 20-fold over the traditional clonal propagation. Seed treatment with 1% KNO3 or 300 ppm GA promoted uniform seed germination and seedling vigour and reduced the transplanting period from 45 days after planting (DAS) to 30 DAS. Removal of taproots of seedlings while transplanting enhanced tuber development. Tuber yield of first clones (C1) was significantly superior to that of the seedlings. The dry matter content and starch output of seedlings and first clones were comparable to that of the commercial varieties. Similarly, the HCN and cooking quality of seedlings and first clones were at acceptable levels. In the open pollinated (OP) progenies of the Ambakadan the CMD infection increased drastically due to secondary spread of the pathogen. The hybrid progenies of Ambakadan and the CMD resistant line MNga-1 revealed higher percentage of CMD free seedlings and first clonal progenies in the evaluation trials conducted at CTCRI Thiruvananthapuram and ARS, Peddapuram during 2001–2002 and 2002–2003. Nearly homogeneous hybrid population resistant to CMD could be obtained by systematic roguing at seedling and first clonal stage. 相似文献
15.
Stability of cassava plants at the DNA level after retrieval from 10 years of in vitro storage 总被引：2，自引：0，他引：2
Summary Cassava (Manihot esculenta Crantz) germplasm collections are conventionally maintained by continuous vegetative propagation in the field. Tissue culture techniques provide a more convenient way to conserve germplasm. The cassava in vitro gene bank held in trust at CIAT comprises nearly 6000 accessions. A study was carried out to determine whether any DNA rearrangements resulting from in vitro storage under slow growth could be detected by molecular analysis in retrieved plants. RFLPs with homologous probes, RAPDs with twenty primers and DNA fingerprinting with M13 probe were tested to detect variation at DNA level in cassava plants after ten-years in vitro storage. The molecular marker data obtained in this study supports the stability of the cassava germplasm under the in vitro storage conditions described in this work. 相似文献
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Tichafa R.I. Munyikwa Jan Kreuze Martin Fregene Luc Suurs Evert Jacobsen Richard G.F. Visser 《Euphytica》2001,120(1):71-83
Screening of a tuber specific cassava cDNA library resulted in the isolation of full length cDNA clones with homology to the
genes encoding the small and large subunits of ADP glucose pyrophosphoryalse. Sequence analysis revealed that AGPase B the
clone with homology to the small subunit shared 54% homology at amino acid level with the AGPase S clone that is more closely
related to the large subunit. Segregation analysis of a cross between the cassava cultivars TMS 30572 and CM 2177-2 revealed
that AGPase S is a single copy gene that is localised on the female derived linkage group E of the cassava genetic map. AGPase
B is a low copy gene of which one member is localised on the female derived linkage group P. The two genes are expressed in
all cassava tissues but AGPase B exhibits a higher steady state mRNA level than AGPase S and is highly expressed in leaf and
tuber tissue. The AGPase enzyme activity was much higher in young cassava leaves as compared to older leaves and tubers. Cassava
AGPase was activated by 3-PGA and inhibited by up to 90% in the presence of inorganic phosphate (Pi). The tuber enzyme was
relatively unaffected by 3PGA but was highly inhibited by Pi. Transformation of potato (Solanum tuberosum) plants with an antisense AGPase B construct resulted in 10 out of 134 antisense AGPase B plants having on average 3.5 times
more tubers than the control non transgenic plants. Analysis of these transgenic plants revealed they had greatly reduced
levels of AGPase B mRNA, 1.5 to 3 times less starch, and five times higher levels of soluble sugars, sucrose, glucose and
fructose, to those found in control plants.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
18.
Alfred G. O. Dixon Malachy O. Akoroda Richardson U. Okechukwu Francis Ogbe Paul Ilona Lateef O. Sanni Chukwuma Ezedinma Jones Lemchi Gorrettie Ssemakula Marie O. Yomeni Emelike Okoro Gbassey Tarawali 《Euphytica》2008,160(1):1-13
The aim of the Integrated Cassava Project (ICP) of the International Institute of Tropical Agriculture was to pre-emptively
manage the cassava mosaic disease (CMD) to avert an imminent and increasing possible threat of the Ugandan strain of the CMD
virus of the pathogen from doing damage to the Nigerian cassava economy. The strategy was to engage in activities that would
lead to cultivar-substitution by replacing the susceptible varieties on farmers’ fields with superior genotypes that are not
only CMD resistant or tolerant but also high yielding with good dry matter content. A fast track participatory selection approach
was used in 2 years to release nine new lines in Nigeria. It was intensive and several lessons were learnt. The varieties
released after 2 years were TMS 98/0510, TMS 98/0581, TMS 97/2205, TMS 98/0505, TME 419, TMS 92/0326, TMS 96/1632, TMS 98/0002,
and TMS 92/0057. 相似文献
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Twenty-eight cassava genotypes from Mozambique, along with seven genotypes from Angola, Madagascar, Nigeria, Togo, Columbia,
and Thailand for comparison, were fingerprinted using random amplified polymorphic DNA (RAPD) analysis. The Mozambican material
represented a wide range of landraces. A total of 311 scored RAPD loci were used to calculate genetic distances between the
genotypes. This revealed an average genetic distance of 3.1% between all the germplasm. The average genetic distance between
the Mozambiquen genotypes was 2.7%, whilst the seven accessions from the other countries showed an average distance of 3.4%.
Neighbor-joining (NJ) method cluster analysis of the genetic distance yielded a tree that did not indicate a relationship
between geographic distribution and genetic diversity.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献