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Characterization of cassava genetic resources | Cassava genetic resources | Crops CGKB | Resources | Genebank Platform

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Characterization of cassava genetic resources

Contributors to this page: CIAT, Colombia (Daniel Debouck); IITA, Nigeria (Dominique Dumet); Bioversity International/ILRI, Ethiopia (Alexandra Jorge); independent consultant (Clair Hershey); INIA, Peru (Llerme Rios); Bioversity International, Rome (Adriana Alercia).

Characterization of cassava germplasm (and many clonal crops) is particularly important for the following purposes:

Contents:
Cultural practices
Descriptors
Information

Planting and cultural practices for characterization

Clonal crops are usually characterized during field regeneration. See also the regeneration page for the complete details of cultural practices.


Field planting for characterization and evaluation in the cassava genebank at CIAT (photo: C. Hershey)

Environment

Plot size

Sampling area/border area

Plant density

Replications

Standard check cultivars

Frequency of standard checks

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Descriptors

Morphological descriptors for characterization

The list of suggested descriptors below is from Fukuda et al. (2010), who developed a descriptor list for IITA. This is based on descriptors used by both CIAT (Colombia) and EMBRAPA (Brazil), and thus encompasses the world’s major cassava collections. The publication includes a full complement of colour photos to facilitate understanding of the states of each descriptor.

Descriptors to be scored at three months after planting

Descriptors to be scored at six months after planting

Descriptors to be scored at nine months after planting


Measuring branching height, one of the cassava standard descriptors (photo: H. Ceballos)

Descriptors to be scored at harvest

*Descriptors in the list of key access and utilization descriptors developed by Bioversity International and CIAT (2009).

In addition to the above, any other local quality traits of importance could be included. New traits identified by industry should be considered for inclusion, such as the ratio of amylose to amylopectin.

Pictures for characterization

Sufficient detail should be captured in images to taxonomically identify the plant and demonstrate the traits that show variation.

Herbarium samples for characterization

Molecular descriptors for characterization

Cytological characterization

This type of characterization should be done in specialized laboratories. Cytological characterization, with current available techniques, is not likely to be broadly applied across all accessions of a collection, but might be targeted to sub-samples such as the core collection.

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Recording information during characterization

References and further reading

Bertram RB. 1993. Application of molecular techniques to genetic resources of cassava (Manihot esculenta Crantz, Euphorbiaceae): interspecific evolutionary relationships and intraspecific characterization. University of Maryland. (PhD thesis).

Bioversity International, CIAT. 2009. Key access and utilization descriptors for cassava genetic resources. Bioversity International, Rome, Italy, International Center for Tropical Agriculture (CIAT), Cali, Colombia. Available here.

Fregene M, Vargas I, Ikea J, Angel F, Thome J, Asiedu RA, Akoroda MO, Roca WM. 1994. Variability of chloroplast DNA and nuclear ribosomal DNA in cassava (Manihot esculenta Crantz) and its wild relatives. Theor. Appl. Genet. 89:719-727.

Fukuda WMG, Guevara CL.1998. Descritores morfológicos e agronómicos para a caracterização de madioca (Manihot esculenta Crantz). [Morphological and agronomic descriptors for characterizing cassava (Manihot esculenta Crantz] Documentos CNPMF no. 78. EMBRAPA/CNPMF. Cruz das Almas BA, Brazil.

Fukuda WMG, Guevara CL, Kawuki R, Ferguson ME. 2010. Selected morphological and agronomic descriptors for the characterization of cassava. International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria. 19 pp. Available from: http://www.iita.org/c/document_library/get_file?uuid=4530a72e-917d-4801-9239-cb0ee3a4dd4e&groupId=25357. Date accessed: 30 September 2010.

Gulick P, Hershey C, Esquinas Alcazar J. 1983. Genetic Resources for cassava and wild relatives. Series AGPG:IBPGR/82/111. IBPGR Secretariat, Rome. 56 pp.

Iwanaga M, Ayala ME, Ocampo CH, Hershey C. 1993. Caracterización de la colección de Colombia del germoplasma de yuca (Manihot esculenta Crantz) por electroforesis PAGE utilizando la isoenzima aß-esterasa. In: Clausen AM, editor. Recursos genéticos hortícolas, Instituto Nacional de Tecnología Agropecuaria, Balcarce, Argentina. pp. 244-258.

Ocampo CH, Hershey C, Iglesias C, Iwanaga M. 1993. Esterase isozyme fingerprinting of the cassava germplasm collection held at CIAT. In: Roca WM, Thro AM, editors. Proceedings of the First International Scientific meeting of the Cassava Biotechnology Network (CBN), Cartagena, Colombia, 25-28 August 1992, Cali, Colombia: CIAT (Working Document No. 123). pp. 81-89.

Ocampo CH, Angel F, Jímenez A, Jaramillo G, Hershey C, Granados E, Iglesias C. 1995. DNA fingerprinting to confirm possible genetic duplicates in cassava germplasm. In: Roca WM, Thro AM, editors. Proceedings of the Second International Scientific meeting of the Cassava Biotechnology network. Bogor, Indonesia, 22-26 August 1994. Working Document No. 150. Centro Internacional de Agricultura Tropical (CIAT). Cali, Colombia. pp. 145-151.

Roca, WM, Rodriguez JA, Roa J. 1983. Procedures for Recovering Cassava and Sweet potato Germplasm Distributed In vitro. Genetic Resource Unit CIAT Apartado Aéreo 6713 Call, Colombia S.A . Available from: http://www.scribd.com/doc/35771901/Manual-for-TC-Cassava-Sweet-Potato. Date accessed: 27 August 2010.

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The Genebanks

The 11 CGIAR genebanks currently conserve 730,000 of cereals and grain legumes, forage crops, tree species, root and tuber crops, bananas and crop wild relatives.

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