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Biological differences and molecular variability between six phenotypically distinct tobacco-infecting geminivirus isolates from southern Africa (Zimbabwe) and Mexico were investigated. Host range studies conducted with tobacco virus isolates ZIM H from Zimbabwe and MEX 15 and MEX 32 from Mexico indicated all had narrow host ranges restricted to the(More)
African cassava mosaic virus (ACMV) and East African cassava mosaic virus (EACMV) are whitefly-transmitted geminiviruses (WTGs) which are widespread in cassava in Africa and cause serious yield losses. Recently, a new geminivirus affecting cassava in South Africa (SACMV) has been reported. In this work SACMV was found to have DNA-A and DNA-B components.(More)
We analysed the sequence diversity in the reverse transcriptase (RT)/ribonuclease H (RNaseH) coding region of 19 badnavirus isolates infecting yam (Dioscorea spp.) in Ghana, Togo, Benin, and Nigeria. Phylogenetic analysis of the deduced amino acid sequences revealed that the isolates are broadly divided into two distinct species, each clustering with(More)
Complementary DNAs encompassing the coat protein coding and adjacent regions ofAgropyron mosaic virus (AgMV) andHordeum mosaic virus (HoMV) were cloned and sequenced. Comparison with other sequenced potyviruses indicated that each clone contained the 3′-non-coding region (3′NCR), the coat protein (CP) gene and part of the nuclear inclusion protein (NIb)(More)
Knowledge and technology transfer to African laboratories and farmers is an important objective for achieving food security and sustainable crop production on the sub-Saharan African continent. Cassava (Manihot esculenta Crantz) is a vital source of calories for more than a billion people in developing countries, and its potential industrial use for starch(More)
ThePotyviridae family has been divided into four genera on the basis of vector transmission, as follows:Potyvirus genus (aphid),Rymovirus genus (mite),Bymovirus genus (fungus) andIpomovirus genus (whitefly). However recent sequence comparisons of the coat protein and 3′ NCR regions of the potyviruses have demonstrated that the rymoviruses appear to be a(More)
The 2094 nucleotides at the 3′-terminus of a South African isolate of ryegrass mosaic virus (RGMV) was cloned and sequenced. Two putative poly-protein cleavage sites were found: Q/L and E/A, both of which are novel in thePotyviridae. The RGMV-SA cDNA was cloned into an expression vector, pUEX, and a fusion protein of 185 kDa was obtained which reacted(More)
The family Geminiviridae comprises a group of plant-infecting circular ssDNA viruses that severely constrain agricultural production throughout the temperate regions of the world, and are a particularly serious threat to food security in sub-Saharan Africa. While geminiviruses exhibit considerable diversity in terms of their nucleotide sequences, genome(More)
Infection of plant cells by viral pathogens triggers RNA silencing, an innate antiviral defense mechanism. In response to infection, small RNAs (sRNAs) are produced that associate with Argonaute (AGO)-containing silencing complexes which act to inactivate viral genomes by posttranscriptional gene silencing (PTGS). Deep sequencing was used to compare(More)
 In this paper we describe results obtained from screening field populations of begomoviruses from infected cassava from six countries in southern Africa. It was found that African cassava mosaic virus occurs in five of the six countries (except Angola), East African cassava mosaic virus is present in five countries (except Zambia) and South African cassava(More)