The Experts below are selected from a list of 10815 Experts worldwide ranked by ideXlab platform
Doyle Mckey - One of the best experts on this subject based on the ideXlab platform.
-
domestication and diversity in manioc Manihot Esculenta crantz ssp Esculenta euphorbiaceae
Current Anthropology, 2008Co-Authors: Laura Rival, Doyle MckeyAbstract:Recent work reviewed here offers new insights into the evolution of manioc (Manihot Esculenta) under domestication and contributes to current scientific efforts aimed at documenting forms of environmental management, local knowledge systems, and cultural practices that enhance genetic diversity. This work shows that human and natural selection jointly shape manioc diversity through (1) the overall cultivation system, which is highly adapted to environmental pressures; (2) the knowledge, categorization, and valorization of phenotypically expressed varietal differences; and (3) the incorporation, in this clonally propagated crop, of sexually reproduced plants, which encourages intravarietal diversity and occasionally leads to the creation of new varieties, that is, new categories that are phenotypically distinct and receive a new name before being multiplied. We conclude that genetic research, when placed in an interdisciplinary context, generates new questions for anthropologists working with manioc cultiv...
-
genetic diversity of traditional south american landraces of cassava Manihot Esculenta crantz an analysis using microsatellites
Economic Botany, 2004Co-Authors: Marianne Elias, Doyle Mckey, Gilda Santos Muhlen, Ana Carolina Roa, Joe TohmeAbstract:The extent and structure of the genetic variability of traditional varieties of cassava (Manihot Esculenta Crantz) have been little documented, despite considerable evidence for this cropś great varietal diversity in traditional agroecosystems. We used microsatellite markers to assess the genetic structure of traditional landraces of sweet and bitter cassava collected from five South American sites. As reference, we used a sample of 38 accessions from a world collection of cultivated cassava. For a total of 10 loci examined, we found 15 alleles that were not represented in this sample. Ten of these had been previously detected in wild Manihot species. The geographical structure of genetic variability was weak, but the genetic differentiation between bitter and sweet landraces was significant, suggesting that each form had evolved separately after domestication. Our results showed that traditional landraces form an important source of genetic diversity and merit more attention from managers of crop genetic resources.
Martin Fregene - One of the best experts on this subject based on the ideXlab platform.
-
assessment of genetic diversity among african cassava Manihot Esculenta grantz accessions resistant to the cassava mosaic virus disease using ssr markers
Genetic Resources and Crop Evolution, 2006Co-Authors: Yvonne Lokko, Alfred G. O. Dixon, S K Offei, E Y Danquah, Martin FregeneAbstract:A study was conducted to determine the extent of genetic diversity among African cassava (Manihot Esculenta Crantz) accessions resistant to the cassava mosaic virus disease (CMD), using simple sequence repeat (SSR) markers. The accessions included a breeding stock (clone 58308), five improved lines, 62 CMD resistant and 10 CMD susceptible landraces. Genetic diversity was assessed among accessions in five cluster groups derived from UPGMA analysis on data from 18 SSR primer pairs. Average gene diversity, He, was high in all cluster groups, with an average heterozygosity of 0.591 ± 0.061. The estimator of inbreeding Fis revealed a low level of inbreeding within groups and averaged −0.262 ± 0.142. Gene diversity among all accessions was 51.4% and gene diversity within cluster groups was 46.6%, while 4.8% was due to diversity between the different cluster groups. The amount of genetic differentiation measured by Gst and Fst were 9.6% and 12.1% respectively, indicating a weak genetic structure.
-
dart for high throughput genotyping of cassava Manihot Esculenta and its wild relatives
Theoretical and Applied Genetics, 2005Co-Authors: Ling Xia, Martin Fregene, Kaiman Peng, Shiying Yang, Peter Wenzl, Carmen M De Vicente, Andrzej KilianAbstract:Understanding the distribution of genetic diversity within and among individuals, populations, species and gene pools is crucial for the efficient management of germplasm collections. Molecular markers are playing an increasing role in germplasm characterization, yet their broad application is limited by the availability of markers, the costs and the low throughput of existing technologies. This is particularly true for crops of resource-poor farmers such as cassava, Manihot Esculenta. Here we report on the development of Diversity Arrays Technology (DArT) for cassava. DArT uses microarrays to detect DNA polymorphism at several hundred genomic loci in a single assay without relying on DNA sequence information. We tested three complexity reduction methods and selected the two that generated genomic representations with the largest frequency of polymorphic clones (PstI/TaqI: 14.6%, PstI/BstNI: 17.2%) to produce large genotyping arrays. Nearly 1,000 candidate polymorphic clones were detected on the two arrays. The performance of the PstI/TaqI array was validated by typing a group of 38 accessions, 24 of them in duplicate. The average call rate was 98.1%, and the scoring reproducibility was 99.8%. DArT markers displayed fairly high polymorphism information content (PIC) values and revealed genetic relationships among the samples consistent with the information available on these samples. Our study suggests that DArT offers advantages over current technologies in terms of cost and speed of marker discovery and analysis. It can therefore be used to genotype large germplasm collections.
-
microsatellites in cassava Manihot Esculenta crantz discovery inheritance and variability
Theoretical and Applied Genetics, 1998Co-Authors: P P Chavarriagaaguirre, Joe Tohme, Martin Fregene, M M Maya, Merideth W Bonierbale, Steve Kresovich, Gary KochertAbstract:Fourteen microsatellites containing GA-repeats were isolated and characterized in cassava (Manihot Esculenta Crantz, Euphorbiaceae). Microsatellite heterozygosity (h) was estimated in 48 accessions using (32P)-end-labeled primers and in more than 500 accessions using fluorescence-based genotyping. Heterozygosity values ranged from 0.00 to 0.88 and the number of alleles detected varied from 1 to 15. The reproducibility of allele sizing was also assessed using fluorescence-based genotyping. The average inter-gel size difference was 1.03 nucleotides. Chi-square tests (χ2) were performed to analyse segregation distortion and the linkage between alleles segregating from either or both parents in an F1 mapping population. Most microsatellite loci segregated in the expected 1 : 1, 1 : 2 : 1 or 1 : 1 : 1 : 1 ratio. Linkage was detected between loci segregating from either parent, and segregation distortion from the male parent was detected for locus GA-131. Approximately 80% of the microsatellites detected one or two alleles per accession, suggesting a low degree of microsatellite locus duplication, an unexpected finding for a putative allopolyploid, highly heterozygous species. The high h values of most microsatellites, their amplification in other Manihot taxa and their suitability for high-throughput, fluorescence-based genotyping, make microsatellites the marker of choice for germplasm characterization and saturation of the cassava map.
Joe Tohme - One of the best experts on this subject based on the ideXlab platform.
-
provitamin a accumulation in cassava Manihot Esculenta roots driven by a single nucleotide polymorphism in a phytoene synthase gene
The Plant Cell, 2010Co-Authors: Ralf Welsch, Joe Tohme, Salim Albabili, Jacobo Arango, Cornelia Bar, Bertha Salazar, Jesus Beltran, Paul Chavarriaga, Hernan Ceballos, Peter BeyerAbstract:Cassava (Manihot Esculenta) is an important staple crop, especially in the arid tropics. Because roots of commercial cassava cultivars contain a limited amount of provitamin A carotenoids, both conventional breeding and genetic modification are being applied to increase their production and accumulation to fight vitamin A deficiency disorders. We show here that an allelic polymorphism in one of the two expressed phytoene synthase (PSY) genes is capable of enhancing the flux of carbon through carotenogenesis, thus leading to the accumulation of colored provitamin A carotenoids in storage roots. A single nucleotide polymorphism present only in yellow-rooted cultivars cosegregates with colored roots in a breeding pedigree. The resulting amino acid exchange in a highly conserved region of PSY provides increased catalytic activity in vitro and is able to increase carotenoid production in recombinant yeast and Escherichia coli cells. Consequently, cassava plants overexpressing a PSY transgene produce yellow-fleshed, high-carotenoid roots. This newly characterized PSY allele provides means to improve cassava provitamin A content in cassava roots through both breeding and genetic modification.
-
genetic diversity of traditional south american landraces of cassava Manihot Esculenta crantz an analysis using microsatellites
Economic Botany, 2004Co-Authors: Marianne Elias, Doyle Mckey, Gilda Santos Muhlen, Ana Carolina Roa, Joe TohmeAbstract:The extent and structure of the genetic variability of traditional varieties of cassava (Manihot Esculenta Crantz) have been little documented, despite considerable evidence for this cropś great varietal diversity in traditional agroecosystems. We used microsatellite markers to assess the genetic structure of traditional landraces of sweet and bitter cassava collected from five South American sites. As reference, we used a sample of 38 accessions from a world collection of cultivated cassava. For a total of 10 loci examined, we found 15 alleles that were not represented in this sample. Ten of these had been previously detected in wild Manihot species. The geographical structure of genetic variability was weak, but the genetic differentiation between bitter and sweet landraces was significant, suggesting that each form had evolved separately after domestication. Our results showed that traditional landraces form an important source of genetic diversity and merit more attention from managers of crop genetic resources.
-
cross species amplification of cassava Manihot Esculenta euphorbiaceae microsatellites allelic polymorphism and degree of relationship
American Journal of Botany, 2000Co-Authors: Paul Chavarriagaaguirre, Merideth W Bonierbale, Myriam C Duque, Maria M Maya, Carlos Iglesias, Joe TohmeAbstract:Microsatellite amplification was performed on cassava (Manihot Esculenta) and six other different species (all wild) of the Manihot genus. We used ten pairs of microsatellite primers previously developed from cassava, detecting 124 alleles in a sample of 121 accessions of the seven species. The number of alleles per locus ranged from four to 21 alleles, and allelic diversity was greater in the wild species than in cassava. Seventy-nine alleles, including unique ones, were detected in the wild species but were not found in the crop. The lower level of heterozygosity in some wild species probably resulted from a combination of fine-scale differentiation within the species and the presence of null alleles. Overall, microsatellite primers worked across the genus, but, with increasing genetic distance, success in amplifying loci tended to decrease. No accession of M. aesculifolia, M. carthaginensis,and M. brachylobapresented a banding pattern at locus Ga-140; neither did one appear for M. aesculifolia at locus Ga-13. Previous work with amplified fragment length polymorphism (AFLP) markers and this microsatellite analysis show that these three wild taxa are the most distant relatives of the crop, whereas the wild forms M. Esculenta subsp. flabellifolia and M. Esculenta subsp. peruviana appear to be the closest.
-
microsatellites in cassava Manihot Esculenta crantz discovery inheritance and variability
Theoretical and Applied Genetics, 1998Co-Authors: P P Chavarriagaaguirre, Joe Tohme, Martin Fregene, M M Maya, Merideth W Bonierbale, Steve Kresovich, Gary KochertAbstract:Fourteen microsatellites containing GA-repeats were isolated and characterized in cassava (Manihot Esculenta Crantz, Euphorbiaceae). Microsatellite heterozygosity (h) was estimated in 48 accessions using (32P)-end-labeled primers and in more than 500 accessions using fluorescence-based genotyping. Heterozygosity values ranged from 0.00 to 0.88 and the number of alleles detected varied from 1 to 15. The reproducibility of allele sizing was also assessed using fluorescence-based genotyping. The average inter-gel size difference was 1.03 nucleotides. Chi-square tests (χ2) were performed to analyse segregation distortion and the linkage between alleles segregating from either or both parents in an F1 mapping population. Most microsatellite loci segregated in the expected 1 : 1, 1 : 2 : 1 or 1 : 1 : 1 : 1 ratio. Linkage was detected between loci segregating from either parent, and segregation distortion from the male parent was detected for locus GA-131. Approximately 80% of the microsatellites detected one or two alleles per accession, suggesting a low degree of microsatellite locus duplication, an unexpected finding for a putative allopolyploid, highly heterozygous species. The high h values of most microsatellites, their amplification in other Manihot taxa and their suitability for high-throughput, fluorescence-based genotyping, make microsatellites the marker of choice for germplasm characterization and saturation of the cassava map.
Laura Rival - One of the best experts on this subject based on the ideXlab platform.
-
domestication and diversity in manioc Manihot Esculenta crantz ssp Esculenta euphorbiaceae
Current Anthropology, 2008Co-Authors: Laura Rival, Doyle MckeyAbstract:Recent work reviewed here offers new insights into the evolution of manioc (Manihot Esculenta) under domestication and contributes to current scientific efforts aimed at documenting forms of environmental management, local knowledge systems, and cultural practices that enhance genetic diversity. This work shows that human and natural selection jointly shape manioc diversity through (1) the overall cultivation system, which is highly adapted to environmental pressures; (2) the knowledge, categorization, and valorization of phenotypically expressed varietal differences; and (3) the incorporation, in this clonally propagated crop, of sexually reproduced plants, which encourages intravarietal diversity and occasionally leads to the creation of new varieties, that is, new categories that are phenotypically distinct and receive a new name before being multiplied. We conclude that genetic research, when placed in an interdisciplinary context, generates new questions for anthropologists working with manioc cultiv...
Zary Shariman Yahaya - One of the best experts on this subject based on the ideXlab platform.
-
in vitro ovicidal and larvicidal activity of methanolic leaf extract of Manihot Esculenta cassava on susceptible and resistant strains of trichostrongylus colubriformis
Veterinary Parasitology, 2012Co-Authors: A Alrofaai, Wahab A Rahman, S F Sulaiman, Zary Shariman YahayaAbstract:Abstract This study aimed to represent the first report of the ovicidal and larvicidal activity of the methanolic leaf extract of Manihot Esculenta (cassava) against eggs and larvae of susceptible and resistant strains of Trichostrongylus colubriformis. As well as, to determine the total tannin compounds, antioxidant activity and toxicity of the extract. The egg hatch test was used to evaluate ovicidal activity against unembryonated eggs, whereas larval feeding inhibition assay and MTT-formazan assay were used to evaluate larvicidal activity against first (L1) and infective (L3) larvae, respectively. The results showed no significant differences were detected between the sensitivities of susceptible and resistant strains of T. colubriformis to the extract. Eggs, L1 and L3 were significantly affected (P