1,720,963 research outputs found
Integrating environmental, socio-economic, and biological data in a farmer-led potato trial for enhanced varietal assessment in Rwanda
Full text linkPotato (Solanum tuberosum L.) is crucial for food security in Rwanda, but its production growth has slowed. Improved potato varieties are urgently needed for Rwanda potato farmers. Crop breeding can effectively support smallholder farmers when it aligns with their environmental conditions and preferences. Additionally, integrating citizen science into variety development can enhance variety adoption and suitability for smallholder farmers. We assessed the insights from a crop trial following a triadic comparison of technology options (tricot) approach, linking the results with environmental, socio-economic, and on-station trial data. Under a tricot trial, 460 farmers tested eleven potato varieties, randomly allocated in incomplete blocks of three, allowing each farmer to test and compare three varieties. Biological data, reflecting breeding and variety genotypic values, were generated from multi-environmental tests conducted during 2018–2019 to evaluate the adaptability of new varieties. This research revealed that Rwandan farmers preferred the pre-1990 varieties (Cruza and Kirundo), while Gisubizo and Kazeneza, post-2018 varieties, were also considered competitive. Farmers’ preferences were influenced by diverse environmental and socio-economic conditions, with taste being crucial for home consumption and yield prioritized for market sales. Additionally, seasonal temperatures influenced the yield performance ranking of potato varieties across regions, while economic considerations and gender dynamics shaped different patterns of variety preferences. Despite challenges in aligning on-station and on-farm data, our integrated approach provides actionable insights for breeding programmes to develop potato varieties that better align with farmers’ needs, as well as environmental and socio-economic conditions. This innovative method can enhance breeding efficiency, variety adoption, and potato productivity, contributing to food security and agricultural sustainability.publishedVersio
Breeding of sweetpotato (Ipomoea batatas (L.) Lam) for drought tolerance and high dry matter content in Rwanda.
Full text linkDoctor of Philosophy in Plant Breeding.Sweetpotato is the third most important root crop next to cassava and potato in Rwanda.
Drought stress remains the leading abiotic constraint to sweetpotato production in the
Southern and Eastern Provinces of the country. Therefore, development and release of
improved sweetpotato varieties incorporating end users’ preferences such as high storage
root yields and dry matter content under limited water conditions remains important for
sustainable production. The specific objectives of this research were: (i) to assess farmers’
perception, production constraints, preferences, and breeding priorities of sweetpotato in
selected agro-ecologies of Rwanda, (ii) to characterise and identify breeding parents among
54 sweetpotato genotypes grown in Rwanda, East and Central Africa, (iii) to select drought
tolerant sweetpotato genotypes under managed drought conditions using greenhouse and
in-vitro screening techniques with early and late developmental traits, (iv) to determine
general combining ability (GCA), specific combining ability (SCA) and maternal effects and
heritability of drought tolerance and yield components of among newly developed
sweetpotato clones and (v) to determine genotype x environment interaction and yield
stability of sweetpotato breeding clones recently bred in Rwanda and to identify promising
genotypes.
A participatory rural appraisal (PRA) study was carried out involving 495 farmers in eight
representative districts to identify farmers’ perception, production constraints, preferences,
and breeding priorities of sweetpotato in the Eastern, Southern and Northern Provinces of
Rwanda. Sweetpotato ranked among the five important food crops for food security and
income generation. Drought stress, unavailability of improved cultivars and planting material,
and pest and disease damage were perceived to be the five main constraints limiting
sweetpotato production. The most important sweetpotato cultivar traits were high yield, early
maturity, drought tolerance, disease and pest resistance, and good culinary taste. The
characteristics of good storage roots identified by farmers included, high dry matter content,
good culinary taste, good shape, root size, and sweetness. Each agro-ecological zone has
its own specific sweetpotato production constraints and farmers’ preferences, necessitating
targeted breeding of different sweetpotato cultivars for each agro-ecological zone for
enhanced productivity and successful adoption of cultivars.
Fifty four sweetpotato genotypes grown in Rwanda, East and Central Africa were field
evaluated to identify breeding parents. Genotypes K513261, Kwezikumwe, 8-1038 and
2005-110 had the highest flowering rate of 44.97, 20.63, 19.05, and 14.82%, respectively.
Suitable genotypes such as K513261, Purple 297, Kwezikumwe and New Kawogo were
identified with high storage root yields at 31.9, 28.6, 28.2 and 27.1 t ha-1, respectively.
Genotypes Ukerewe, 2005-103, Meresiyana and Mvugamo showed the highest mean dry
matter content at 36.5, 35.5, 35.3 and 34.0%, respectively.
Greenhouse and in-vitro screening methods were compared for effective selection of
drought tolerance using 54 diverse sweetpotato genotypes. Positive correlations were
observed between vine yield and fresh weight gain; and between total biomass and fresh
weight gain, during greenhouse and in-vitro studies, respectively. The genotypes 2005-146,
4-160, 8-1038, Karibunduki, Kwezikumwe, Purple 4419, NASPOT 9 O, Nsasagatebo,
Karebe, IMBY 3102, Mwanakumi, 97-062 and Matembere were selected with comparatively
high drought tolerance using the two screening procedures. The genotypes 2005-020,
K513261, Kwezikumwe and Otada 24 were selected for high yield of storage roots, while
2005-034, 2005-110, SPK004 and Ukerewe were selected for high dry matter content, and
4-160, 8-1038, Nsasagatebo and Purple 4419 selected for high drought tolerance. The
selected genotypes have a high flowering rate and are potential parents to breed for high
yield and dry matter content of storage roots and drought tolerance.
Twelve genotypes selected for their high yield, dry matter content or drought tolerance were
crossed using a full diallel mating design. Families were field evaluated at Masoro, Karama
and Rubona Research Stations of Rwanda Agriculture Board to determine general
combining ability (GCA), specific combining ability (SCA), maternal effects and heritability of
drought tolerance, yield and yield components. The GCA effects of parents and SCA effects
of crosses were significant (P<0.01) for canopy temperature (CT), canopy wilting (CW),
storage root, vine and biomass yields, and dry matter content of storage roots. The best
general combiners for drought tolerance were the parents 8-1038, Otada 24 and 4-160 with
the lowest CT and CW and relatively high yields. Best combiners for high storage roots yield
were the parents Nsasagatebo, K513261 and Ukerewe, while Nsasagatebo, 2005-034 and
Ukerewe were the best combiners for high dry matter content. Maternal effects were
significant (P<0.05) among families for CT, CW, flesh color and dry matter content, vine yield
and total biomass. Based on reduced CT and CW, the best families with significant SCA
effects were 4-160 x Nsasagatebo, 4-160 x Ukerewe, Otada 24 x 4-160, Nsasagatebo x
2005-020, Otada 24 x Nsasagatebo, 4-160 x K513261 , 513261 x 4-160, 8-1038 x 4-160, 4-
160 x 8-1038, 8-1038 x 2005-020 and Nsasagatebo x Ukerewe, which were selected for
breeding for drought tolerance. Across sites, the best five selected families with significant
SCA effects for storage root yields were Nsasagatebo x Otada 24, Otada 24 x Ukerewe, 4-
160 x Nsasagatebo, K513261 x 2005-034 and Ukerewe x K513261 with 11.0, 9.7, 9.3, 9.2,
8.6 t/ha, respectively. The best families with high dry matter content of 36.1, 35.1, 34.3,
34.0, and 33.9% were Ukerewe x 2005-034, 4-160 x Nsasagatebo, 2005-034 x Ukerewe,
2005-034 x K513261, 2005-020 x Ukerewe, in that order. The selected families are valuable
genetic resources for sweetpotato breeding for drought tolerance, yield and yield
components. Genotype by environment interaction and yield stability of 45 selected sweetpotato breeding
clones were evaluated across six environments in Rwanda. Candidate clones designated as
clone 21 (4-160 x 2005-020), 137 (K513261 x 2005-034) and 22 (4-160 x 2005-020) had the
highest storage root yields of 38.2, 23.4 and 20.8 t ha-1, respectively. The highest dry matter
content of storage roots of 40.6, 35.9 and 32.9% were recorded in clones 21, 137 and 259
(2005-034 x 8-1038), respectively. AMMI stability values (ASV) revealed the following most
stable genotypes: Nsansagatebo, 210 (8-1038 x 4-160), 2005-110 and 456 (SPK004 x
K513261), for storage root yields and clones 46 (Kwezikumwe x 2005-020), 509 (Ukerewe x
Kwezikumwe), and 358 (Ukerewe x 8-1038) for dry matter content of storage roots. The
study identified high yielding and stable candidate sweetpotato clones such as 21, 137 and
22 (4-160 x 2005-020) for their high yields and dry matter content of storage roots. These
clones are recommended for direct production or sweetpotato breeding programmes in
Rwanda and similar environments
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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