Plant Genetic Resources

Research Article

Genetic diversity of cassava (Manihot esculenta Crantz) landraces and cultivars from southern, eastern and central Africa

R. S. Kawukia1a2a3, L. Herselmana2, M. T. Labuschagnea2, I. Nzukia3a4, I. Ralimananaa5, M. Bidiakaa6, M. C. Kanyangea7, G. Gashakaa7, E. Masumbaa8, G. Mkamiloa8, J. Gethia9, B. Wanjalaa9, A. Zacariasa10, F. Madabulaa10 and M. E. Fergusona3 c1

a1 National Crops Resources Research Institute (NaCRRI), PO Box 7084, Kampala, Uganda

a2 Department of Plant Sciences, University of the Free State, PO Box 339, Bloemfontein 9300, South Africa

a3 International Institute of Tropical Agriculture (IITA), PO Box 30709, Nairobi, Kenya

a4 Bioscience eastern and central Africa, c/o International Livestock Research Institute, PO Box 30709, Nairobi, Kenya

a5 FOFIFA/DRA, PO Box 1444, Antananarivo, Madagascar

a6 Institut National pour l'Etude et la Recherche Agronomique (INERA), Kinshasa, Democratic Republic of Congo

a7 Institut des Sciences Agronomiques du Rwanda (ISAR), BP 138, Butare, Rwanda

a8 Root and Tuber Research Program, Naliendele Agricultural Research Institute, PO Box 509, Mtwara, Tanzania

a9 Kenya Agricultural Research Institute (KARI), Katumani, PO Box 340, Machakos, Kenya

a10 Agricultural Research Institute (IIAM), PO Box 1922, Maputo, Mozambique

Abstract

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.

(Received October 19 2012)

(Accepted January 06 2013)

(Online publication February 12 2013)

Key Words:

  • Africa;
  • cassava;
  • genetic differentiation;
  • genetic diversity;
  • Manihot esculenta Crantz;
  • simple sequence repeats

Correspondence

c1 Corresponding author. E-mail: m.ferguson@cgiar.org

0Comments