Document Type Doctoral Thesis Author Ndunguru, Joseph URN etd-02272006-092153 Document Title Molecular characterization of cassava mosaic geminiviruses in Tanzania Degree PhD Department Microbiology and Plant Pathology Supervisor
Advisor Name Title Prof A S Aveling Keywords
- cassava mosaic geminiviruses
- African cassava mosaic virus
- cassava mosaic disease
- East AFrican cassava mosaic virus
- DNA-B molecular characterisation
Date 2005-08-06 Availability restricted AbstractCassava (Manihot esculenta Crantz) is a basic staple food crop in Tanzania. Cassava mosaic disease (CMD) caused by cassava mosaic geminiviruses (CMGs) constitutes a major limiting factor to cassava production in the country. This study was undertaken to characterize the CMGs occurring in Tanzania using molecular techniques and to map their geographical distribution to generate information on which the formulation of control measures can be based. Using Polymerase Chain Reaction (PCR) and Restriction Fragment Length Polymorphism (RFLP) for analysis of CMGs DNA-A genomes, different CMGs were found to be associated with CMD. Higher molecular diversity was observed among East African cassava mosaic viruses (EACMVs)
than African cassava mosaic viruses (ACMVs), which was confirmed later by complete
nucleotide sequence analysis. In addition to EACMV and ACMV isolates, two isolates of
EACMV Cameroon virus (EACMCV) were found in Tanzania. These were confirmed to be strains of EACMCV Cameroon, originally described in Cameroon, West Africa and here named EACMCV- [TZ1] and EACMCV-[TZ7]. They had high (92%) overall DNA-A nucleotide sequence identity and EACMCV-[TZ1] was widespread in the southern part of the country. A subgenomic DNA form of CMG that appeared to be truncated was identified in a CMD-infected cassava plant. It was confirmed upon sequence analysis to be a defect of EACMV DNA-A and had a capacity of attenuating symptoms when coinoculated with wild-type EACMV. In addition, this study revealed for the first time the presence of two novel non-geminivirus single-stranded DNA (ssDNA) sub-genomic molecules associated with CMG infection. They were shown to be dependent on CMG for replication and movement within the plants, confirming their status as satellite molecules named here as satDNA-II and satDNA-III. When present in coinfection with CMGs, they enhance symptoms and can break high levels of resistance in a cassava landrace. Finally a simple, inexpensive technique is described of archiving, transporting and recovering plant DNA for downstream geminivirus characterisation.
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28.8 Modem 56K Modem ISDN (64 Kb) ISDN (128 Kb) Higher-speed Access 00front.pdf 115.64 Kb 00:00:32 00:00:16 00:00:14 00:00:07 < 00:00:01 01chapter1.pdf 109.82 Kb 00:00:30 00:00:15 00:00:13 00:00:06 < 00:00:01 02chapter2.pdf 395.56 Kb 00:01:49 00:00:56 00:00:49 00:00:24 00:00:02 03chapter3.pdf 2.06 Mb 00:09:31 00:04:53 00:04:17 00:02:08 00:00:10 04chapter4.pdf 1.07 Mb 00:04:58 00:02:33 00:02:14 00:01:07 00:00:05 05chapter5.pdf 3.02 Mb 00:13:57 00:07:10 00:06:16 00:03:08 00:00:16 06chapter6.pdf 1.60 Mb 00:07:24 00:03:48 00:03:20 00:01:40 00:00:08 07chapter7.pdf 726.29 Kb 00:03:21 00:01:43 00:01:30 00:00:45 00:00:03 08chapter8.pdf 124.30 Kb 00:00:34 00:00:17 00:00:15 00:00:07 < 00:00:01indicates that a file or directory is accessible from the campus network only.