Welcome to MELSpace
DSpace is a digital service that collects, preserves, and distributes digital material. Repositories are important tools for preserving an organization's legacy; they facilitate digital preservation and scholarly communication.
Recent Submissions
ICARDA 2024 Financial Statement
Author(s): (ICARDA), International Center for Agricultural Research in the Dry Areas (International Center for Agricultural Research in the Dry Areas (ICARDA), 2024-12-31)
Date: 2024-12-31
Type: Report
Status: Open access
ICARDA's Financial Report offers a meticulous examination of our financial achievements, underscoring our unwavering commitment to transparency, effectiveness, and responsible fiscal stewardship. The report provides invaluable perspectives on income origins, expenditure distribution, investment tactics, and critical financial benchmarks. As we persist in propelling agricultural research and pioneering breakthroughs in arid regions, this report serves as a testament to our unwavering dedication to sound financial strategies, bolstering our mission to enrich livelihoods and foster sustainable development.
Differences in Manioc Diversity Among Five Ethnic Groups of the Colombian Amazon
Author(s): Peña-Venegas, Clara; Stomph, Tjeerd; Verschoor, Gerard; Becerra, Augusto; Struik, Paul C. (MDPI, 2014-12-09)
Date: 2014-12-09
Type: Journal Article
Status: Open access
Manioc is an important root crop in the tropics and the most important staple food in the Amazon. Manioc is diverse but its diversity has not yet been clearly associated with environmental or social factors. Our study evaluates how variation in edaphic environments and in social factors influences manioc diversity among five ethnic groups of the Amazon region of Colombia. Inventories of landraces, genetic analysis of manioc diversity, visits to farmers’ swiddens and interviews with farmers were carried out during two years of field work. Morphotypic and genotypic diversity of manioc were large. The different ethnic groups of our study cultivate different sweet and bitter manioc landraces which they select and maintain in accordance with their ancestral rules and norms. Differences in available environments among indigenous communities (such as the presence of different soils) did not markedly affect manioc morphotypic or genotypic diversity, while social factors considerably influenced observed manioc diversity. Manioc diversity was explained by two parallel processes of manioc diversification: volunteer seedling selection and manioc seed exchange. We argue that, for a full understanding of manioc diversity, indigenous knowledge, as well as morphological and genetic variation should be taken into account.
Identification of genes that have undergone adaptive evolution in cassava (Manihot esculenta) and that may confer resistance to cassava brown streak disease
Author(s): Ferguson, Morag; Koga, T.M.; Johnson, D.A.; Koga, K.A.; Hirsch, G.N.; Becerra, Augusto; Messier, W. (Academic Journals, 2015-01-14)
Date: 2015-01-14
Type: Journal Article
Status: Open access
Cassava (Manihot esculenta) is a vital food security crop and staple in Africa, yet cassava brown streak disease (CBSD) and cassava mosaic disease result in substantial yield losses. The aim of this study was to identify genes that have undergone positive selection during adaptive evolution, from CBSD resistant, tolerant and susceptible M. esculenta varieties and inter-specific hybrids, as well as a wild cassava species. Transcriptomes of 13 genotypes were sequenced and three genes with strong positive selection were detected (designated as EG2771, EG964 and EG5651). Sequence variation for candidate genes in 18 different cassava genotypes was examined in relation to known response to CBSD and whitefly infection. Although, we cannot ascribe a selection pressure that was responsible for the observed positive selection with complete certainty at this stage, given the congruence of the pattern of particular alleles of our positively selected genes and the pattern of disease resistance of the cassava varieties we examined, it is likely that some protein variants coded by alleles of EG2771 and EG964 may be associated with CBSD and whitefly resistance responses. This warrants further investigation. Other alleles of our positively selected genes were likely influenced by domestication or some other unknown selective pressure.
A genetic map of cassava (Manihot esculenta Crantz) with integrated physical mapping of immunity-related genes
Author(s): Soto, Johana Carolina; Ortiz, Juan Felipe; Perlaza-Jiménez, Laura; Vásquez, Andrea Ximena; Becerra, Augusto; Mathew, Boby; Leon, Jens; Bernal, Adriana; Ballvora, Agim; Lopez, Camilo (BioMed Central, 2015-03-16)
Date: 2015-03-16
Type: Journal Article
Status: Open access
Background
Cassava, Manihot esculenta Crantz, is one of the most important crops world-wide representing the staple security for more than one billion of people. The development of dense genetic and physical maps, as the basis for implementing genetic and molecular approaches to accelerate the rate of genetic gains in breeding program represents a significant challenge. A reference genome sequence for cassava has been made recently available and community efforts are underway for improving its quality. Cassava is threatened by several pathogens, but the mechanisms of defense are far from being understood. Besides, there has been a lack of information about the number of genes related to immunity as well as their distribution and genomic organization in the cassava genome.
Results
A high dense genetic map of cassava containing 2,141 SNPs has been constructed. Eighteen linkage groups were resolved with an overall size of 2,571 cM and an average distance of 1.26 cM between markers. More than half of mapped SNPs (57.4%) are located in coding sequences. Physical mapping of scaffolds of cassava whole genome sequence draft using the mapped markers as anchors resulted in the orientation of 687 scaffolds covering 45.6% of the genome. One hundred eighty nine new scaffolds are anchored to the genetic cassava map leading to an extension of the present cassava physical map with 30.7 Mb. Comparative analysis using anchor markers showed strong co-linearity to previously reported cassava genetic and physical maps. In silico based searching for conserved domains allowed the annotation of a repertory of 1,061 cassava genes coding for immunity-related proteins (IRPs). Based on physical map of the corresponding sequencing scaffolds, unambiguous genetic localization was possible for 569 IRPs.
Conclusions
This is the first study reported so far of an integrated high density genetic map using SNPs with integrated genetic and physical localization of newly annotated immunity related genes in cassava. These data build a solid basis for future studies to map and associate markers with single loci or quantitative trait loci for agronomical important traits. The enrichment of the physical map with novel scaffolds is in line with the efforts of the cassava genome sequencing consortium.
Assessment of cassava (Manihot esculenta Crantz) diversity, loss of landraces and farmers preference criteria in southern Benin using farmers’ participatory approach
Author(s): Agre, Angelot; Bhattacharjee, Ranjana; Dansi, Alexandre; Becerra, Augusto; Dansi, M.; Sanni, Ambaliou (Springer (part of Springer Nature) (Springer Open Choice Hybrid Journals), 2017-02-01)
Date: 2015-12-11
Type: Journal Article
Status: Timeless limited access
Cassava (Manihot esculenta Crantz) is one of the highly produced and consumed food crops in Benin Republic. Through the application of participatory research appraisal tools and techniques, such as direct observations, group discussions and field visit, cassava production constraints, the diversity at the community level and farmers’ varieties preference criteria were assessed in southern Benin. Base on national statistic cassava production fifty five (55) villages were selected and surveyed in the southern Benin. Descriptive statistics were used to analyse the data collected. About 11 constraints were listed by farmers, and the most important were low productivity, low post-maturity underground storage capacity of the roots of some cultivars, viral disease (cassava mosaic disease), susceptibility to high soil moisture, and lack of early maturing cultivars, which together accounted for 68.02 % of the total responses. Additionally, a total of 125 existing landraces were recorded. The distribution and extent pattern revealed 59 elites cultivars (cultivated by many households and on large areas) that were further grouped into 23 categories based on their agronomic, technological and culinary characteristics. In most of the villages, the farmers’ perception of cultivar loss was based on abandonment of some cultivars due to their poor agronomic (69.12 % of responses) and culinary and/or technological attributes (30.88 % of responses). Within the existing diversity, cultivar choice or preferences are based on 22 culinary, technological, agronomic and economic criteria and their importance vary across the different department. Among these criteria, the most important were high productivity, good quality of the gari, early maturity and good friability accounted together for 48.12 % of the total responses. The presence of duplicates or synonyms was also observed and it is suggested that both morphological and molecular characterization and classification be carried out for better identification of cultivars.