Cassava (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.
Aveling, T.A.S. (Theresa); Ndunguru, J.; De León, L.; Doyle, C.D.; Sseruwagi, P.; Plata, G.; Legg, J.P.; Thompson, G.; Tohme, J.; Ascencio-Ibáñez, J.T.; Hanley-Bowdoin, L.(American Society for Microbiology, 2016-04)
Cassava mosaic begomoviruses (CMBs) cause cassava mosaic disease (CMD) across Africa and the Indian subcontinent. Like all
members of the geminivirus family, CMBs have small, circular single-stranded DNA genomes. We report ...
Davies, Andrew Byron; Eggleton, Paul; Janse Van Rensburg, Berndt; Parr, Catherine Lucy(Wiley-Blackwell, 2012-02)
1. Fire is an important disturbance in African savannas where it is generally assumed that high levels of pyrodiversity (variation in aspects of the fire regime) are necessary to maintain high levels of biodiversity. There ...
McDurmon, Joel Edward(OpenJournals Publishing, 2012-09-13)
This article reviewed claims made by modern scholars Ford Lewis Battles and G.H.
Williams, as well as charges made by Melanchthon, against Andreas Karlstadt (1486–1541)
in regard to the imposition of Mosaic Law upon the ...