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Genetic and root growth studies in cassava (Manihot esculenta Crantz)

implications for breeding

Balyejusa Kizito, Elizabeth (2006). Genetic and root growth studies in cassava (Manihot esculenta Crantz). Diss. (sammanfattning/summary) Uppsala : Sveriges lantbruksuniv., Acta Universitatis Agriculturae Sueciae, 1652-6880 ; 2006:82
ISBN 91-576-7131-1
[Doctoral thesis]

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Cassava (Manihot esculenta Crantz) is a perennial tropical crop grown for its starch-containing tuberous roots. It is cultivated mainly by small-scale farmers and consumed daily by an estimated 500 million people. Cassava mosaic disease (CMD) has long been recognized as a major limiting factor to cassava production in Africa and severe epidemics hit Uganda in the late 1920’s and late 1980’s. Inspite of its importance as a major food crop it is the least researched major crop and many questions regarding its genetics are still unresolved. This thesis has therefore dealt with studies on: i) the effect of CMD on the genetic diversity of cassava in Uganda, ii) the composition of varieties and the genetic structure within and between varieties on small farms in Uganda, iii) the genetic basis of two agronomic important traits, cyanogenic glucoside potential (CNP) and dry matter content (DMC) in cassava roots, using quantitative trait loci (QTL) mapping and iv) the effect of nutrient availability on the growth and tuber formation. The outcome of these studies is relevant for developing strategies for breeding and gene conservation programmes. CMD did not have a strong selective effect on the genetic diversity of cassava in Uganda in spite of earlier reports on losses of varieties due to the latest CMD epidemic. However, a loss of rare alleles in areas with high CMD incidence in Uganda was found. The composition of varieties differed widely between villages and districts and the genetic variation was surprisingly large within varieties although the variation was larger among varieties. The like-named varieties in different villages were genetically similar, demonstrating farmers’ ability to differentiate and maintain the same variety over large areas. We detected two QTL on two different linkage groups controlling CNP and six QTL on four different linkage groups controlling DMC. One QTL for CNP and one QTL for DMC mapped near each other, suggesting pleiotrophy or linkage of QTL. In the root studies, production of storage roots was found to be regulated by nutrient availability and appeared to be positively affected by a gradually increasing limitation of mineral nutrients during the growth of the plants.

Authors/Creators:Balyejusa Kizito, Elizabeth
Title:Genetic and root growth studies in cassava (Manihot esculenta Crantz)
Subtitle:implications for breeding
Series Name/Journal:Acta Universitatis Agriculturae Sueciae
Year of publishing :2006
Number of Pages:47
ALLI. Balyejusa Kizito, E., Bua, A., Fregene, M., Egwang, T., Gullberg, U. & Westerbergh, A. 2005. The effect of cassava mosaic disease on the genetic diversity of cassava in Uganda. Euphytica 146, 45-54. II. Balyejusa Kizito, E., Chiwona-Karltun, L., Egwang, T., Fregene, M. & Westerbergh, A. 2006. Genetic diversity and variety composition of cassava on small-scale farms in Uganda: an interdisciplinary study using genetic markers and farmer interviews. Genetica (in press). III. Balyejusa Kizito, E., Rönnberg-Wästljung, A.-C., Egwang, T, Gullberg, U., Fregene, M. & Westerbergh, A. 2006. Quantitative trait loci controlling cyanogenic glucoside and dry matter content in cassava roots (Manihot esculenta Crantz). (Submitted). IV. Lundquist, P.-O., Kähr, M., Balyejusa Kizito, E., Gullberg, U. & Westerbergh, A. Growth and nutrient-regulated tuber formation in cassava (Manihot esculenta Crantz. (Submitted).
Place of Publication:Uppsala
ISBN for printed version:91-576-7131-1
Publication Type:Doctoral thesis
Full Text Status:Public
Agrovoc terms:manihot esculenta, cassava, root vegetables, plant breeding, cassava mosaic virus, cyanogenic glycosides, dry matter content, varieties, genetic variation, genetic maps, loci, tubers, plant developmental stages, uganda
Keywords:Cassava breeding, cassava mosaic disease, cyanogenic glucosides, dry matter content, genetic diversity, QTL mapping, quantitative trait loci, tuber formation
Permanent URL:
ID Code:1220
Department:(NL, NJ) > Dept. of Plant Biology and Forest Genetics (until 131231)
Deposited By: Elizabeth Balyejusa Kizito
Deposited On:04 Oct 2006 00:00
Metadata Last Modified:02 Dec 2014 10:10

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