Theses and Dissertations Collection

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Browsing Theses and Dissertations Collection by Author "Fayiah, John Soleemulo"

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    Survey for the expression levels of drought tolerant genes in cassava varieties in Tanzania
    (Sokoine University of Agriculture, 2016) Fayiah, John Soleemulo
    Cassava (Mcmihot esculenia Crantzj is an important root crop to resource-poor farmers in Sub-Sahara Africa, where the production is hampered by drought stress constraints. Given the difficulties associated with cassava breeding, a molecular understanding of drought tolerance in cassava will help in the identification of markers for use in marker-assisted selection and genes for transgenic improvement of drought tolerance. This study was to improve efficiency in breeding for drought tolerance cassava through molecular techniques by determining the expression levels for each drought tolerant genes in eight selected cassava varieties grown in screen-house environment. Results in this study indicated the presence of drought tolerant genes in Kizimbani, KBH 2006/374. KBH 2002/135. UKG 92/053, IS 30474, Kiroba, KBH 95/517 and KBH 97/212. From the four genes (ALDH7B4, ZFP252, MSD and RD28) that have previously been biologically validated as conferring or being associated with drought tolerance in other plant species; ALDH7B4 gene was confirmed as being exclusively up-regulated in all varieties except in IS 30474. Results showed further that the four genes were exclusive up-regulated in Kiroba compared with other cassava varieties. Based on ALDH7B4 gene, it was hypothesized that the basis of the tolerance at the cellular level in those varieties is through mitigation of the osmotic and oxidative adjustment. The ALDH7B4 gene can now be tested in the context of cassava breeding, as possible quantitative trait loci and engineering drought tolerance in transgenic cassava, or used for introgression into other improved cassava germplasms for climate change mitigation.