Antananarivo, Madagascar
Antananarivo, Madagascar

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Kawuki R.S.,National Crops Resources Research Institute NaCRRI | Kawuki R.S.,University of the Free State | Ferguson M.,International Institute Of Tropical Agriculture | Labuschagne M.T.,University of the Free State | And 10 more authors.
Field Crops Research | Year: 2011

An improved understanding of phenotypic variation within cassava germplasm in southern, eastern and central Africa will help to formulate knowledge-based breeding strategies. Thus, the overall objective of this study was to examine the phenotypic variation in cassava germplasm available within six breeding programmes in Africa, namely Uganda, Kenya, Tanzania, Rwanda, Democratic Republic of Congo and Madagascar. In each country, single-row plots were used for assessment of 29 qualitative traits and evaluation of four quantitative traits: root dry matter content (DMC), harvest index (HI), leaf retention (LR) and root cortex thickness. Qualitative traits provided limited discrimination of cassava germplasm. However, differences in DMC, HI, LR and root cortex thickness were observed among the germplasm indicating scope for genetic improvement. Highest average DMC was registered in Uganda (39.3%) and lowest in Tanzania (30.1%), with the elite genotypes having a relatively higher DMC than local genotypes. Highest average HI was observed in Uganda (0.60) and lowest in Kenya (0.32). Cassava genotypes displayed varied root peel thickness (0.34-4.89. mm). This study highlights variation in agronomic traits that could be exploited to increase cassava productivity. © 2011 Elsevier B.V.

Kawuki R.S.,National Crops Resources Research Institute NaCRRI | Kawuki R.S.,University of the Free State | Kawuki R.S.,International Institute Of Tropical Agriculture | Herselman L.,University of the Free State | And 14 more authors.
Plant Genetic Resources: Characterisation and Utilisation | Year: 2013

Studies to quantify genetic variation in cassava germplasm, available within the national breeding programmes in Africa, have been limited. Here, we report on the nature and extent of genetic variation that exists within 1401 cassava varieties from seven countries: Tanzania (270 genotypes); Uganda (268); Kenya (234); Rwanda (184); Democratic Republic of Congo (DRC; 177); Madagascar (186); Mozambique (82). The vast majority of these genotypes do not exist within a formal germplasm conservation initiative and were derived from farmers' fields and National Agricultural Research Systems breeding programmes. Genotypes were assayed using 26 simple sequence repeat markers. Moderate genetic variation was observed with evidence of a genetic bottleneck in the region. Some differentiation was observed among countries in both cultivars and landraces. Euclidean distance revealed the pivotal position of Tanzanian landraces in the region, and STRUCTURE analysis revealed subtle and fairly complex relationships among cultivars and among landraces and cultivars analysed together. This is likely to reflect original germplasm introductions, gene flow including farmer exchanges, disease pandemics, past breeding programmes and the introduction of cultivars from the International Institute of Tropical Agriculture - Nigeria. Information generated from this study will be useful to justify and guide a regional cassava genetic resource conservation strategy, to identify gaps in cassava diversity in the region and to guide breeding strategies. Copyright © 2013 NIAB.

Krishnan S.,University of Colorado at Boulder | Ranker T.A.,National Science Foundation | Davis A.P.,The Herbarium | Rakotomalala J.J.,FOFIFA DRA
Genetic Resources and Crop Evolution | Year: 2013

Madagascar has 59 species of Coffea, of which 42 are listed as Critically Endangered, Endangered, or Vulnerable by criteria of the Red List Category system of the World Conservation Union. In an attempt to assess the conservation value of ex situ collections of Malagasy coffee species, a study was undertaken using the field genebank collections maintained at the Kianjavato Coffee Research Station. Three species were selected for this purpose, C. kianjavatensis, C. montis-sacri, and C. vatovavyensis, and for comparative purposes extant, in situ populations of the same species were studied. Parentage analyses of ex situ propagated offspring of C. kianjavatensis and C. montis-sacri were performed to assess if crossing with other Coffea species maintained in the field genebank is compromising the genetic integrity of the collection. For these three species, higher genetic diversity was observed in the ex situ populations compared to the in situ populations, highlighting the importance of preserving the plants currently in ex situ collections. Parentage analyses of seed-propagated offspring of C. kianjavatensis and C. montis-sacri revealed that cross contamination with pollen from other Coffea species in the ex situ field genebank is occurring. These results have significant implications for the conservation management of wild Coffea species and for the management of ex situ genebanks. © 2012 Springer Science+Business Media Dordrecht.

Krishnan S.,University of Colorado at Boulder | Ranker T.A.,National Science Foundation | Davis A.P.,The Herbarium | Rakotomalala J.J.,FOFIFA DRA
Tree Genetics and Genomes | Year: 2013

Madagascar has 59 described species of Coffea, of which 42 are listed as critically endangered, endangered, or vulnerable by the criteria of the Red List Category system of the World Conservation Union (IUCN). The littoral forest of Madagascar is a distinctive type of humid evergreen forest restricted to unconsolidated sand located within a few kilometers of the Indian Ocean, now persisting only as small fragments with ca. 10 % of its original range remaining. In an attempt to understand the genetic diversity of Madagascan coffee species, we studied ex situ and in situ populations of Coffea commersoniana, an endemic species of the littoral forests of southeastern Madagascar and soon to be impacted by mining activities in that region. The in situ populations studied showed higher genetic diversity than the ex situ population. The genetic partitioning among the two in situ populations of C. commersoniana was high enough to necessitate keeping the two populations separate for restoration purposes. Based on these findings, recommendations for conservation management (in situ and ex situ) are made. © 2012 Springer-Verlag.

Krishnan S.,Center for Global Initiatives | Ranker T.A.,University of Hawaii at Manoa | Davis A.P.,Herbarium | Rakotomalala J.-J.,FOFIFA DRA
Acta Horticulturae | Year: 2015

Coffee genetic resources are being lost at a rapid pace, leading to loss of genetic diversity. Various threats contribute to the erosion of coffee genetic diversity such as human population pressures leading to conversion of land to agriculture, deforestation and land degradation; low coffee prices leading to abandoning of coffee trees in forests and gardens and shifting cultivation to other more remunerative crops; and climate change. Additionally, the cultivated species of coffee (Coffea arabica L.) has a very narrow genetic base. Increased incidence of pests and diseases associated with climate change is leading to significant crop losses, threatening livelihoods in many coffee growing countries. A comprehensive conservation strategy for coffee should take into account complementary methods of in situ and ex situ conservation. The development of molecular techniques has expanded the possibilities and tools for genetic analysis for efficient conservation and use of coffee genetic resources. Before it is too late, a thorough evaluation of existing germplasm should be performed based upon which a comprehensive conservation strategy could be developed. A case study using four different Coffea species in Madagascar is discussed.

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