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African Cassava Mosaic Virus (african + cassava_mosaic_virus)

Distribution by Scientific Domains
Life Sciences100%

Kinds of African Cassava Mosaic Virus

  • east african cassava mosaic virus
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    Selected Abstracts

    Viruses Associated with Cassava Mosaic Disease in Senegal and Guinea Conakry

    JOURNAL OF PHYTOPATHOLOGY, Issue 2 2004
    G. Okao-Okuja
    Abstract A survey in Senegal and Guinea Conakry established the presence and incidence of cassava mosaic virus disease (CMD) in both countries. CMD occurred in all the fields surveyed, although its incidence was higher in Senegal (83%) than in Guinea (64%). Populations of the whitefly vector, Bemisia tabaci, were low in both countries averaging 1.7 adults per shoot in Guinea and 3.2 in Senegal. Most infections were attributed to the use of infected cuttings, 86 and 83% in Senegal and Guinea, respectively, and there was no evidence of rapid current-season, whitefly-borne infection at any of the sampled locations. Disease severity was generally low in the two countries and averaged 2.5 in Guinea and 2.3 in Senegal. No plants with unusually severe CMD symptoms characteristic of the CMD pandemic in East and Central Africa were observed. Restriction fragment length polymorphism (RFLP)-based diagnostics revealed that African cassava mosaic virus (ACMV) is exclusively associated with CMD in both the countries. Neither East African cassava mosaic virus (EACMV), nor the recombinant Uganda variant (EACMV-UG2) was detected in any sample. These survey data indicate that CMD could be effectively controlled in both countries by phytosanitation, involving the use of CMD-free planting material and the removal of diseased plants. [source]

    Resistance to cassava mosaic disease in transgenic cassava expressing antisense RNAs targeting virus replication genes

    PLANT BIOTECHNOLOGY JOURNAL, Issue 4 2005
    Peng Zhang
    Summary African cassava mosaic virus (ACMV) is a major contributor to cassava mosaic disease (CMD), the economically most important and devastating disease of cassava in Africa. We have developed transgenic cassava plants with increased ACMV resistance using improved antisense RNA technology by targeting the viral mRNAs of Rep (AC1), TrAP (AC2) and REn (AC3). Viral DNA replication assays in detached leaves demonstrated that replication of two ACMV isolates was strongly reduced or inhibited in most transgenic lines. After ACMV infection of plants using biolistic inoculation, several lines remained symptomless at lower infection pressure (100 ng viral DNA/plant). Symptom development was reduced and attenuated even at higher DNA doses. Transgenic ACMV-resistant plants had significantly reduced viral DNA accumulation in their infected leaves. Short sense and antisense RNAs specific to AC1 were identified in transgenic lines expressing AC1 antisense RNA, suggesting that the short RNAs mediate interference by post-transcriptional gene silencing. Our results demonstrate that resistance to ACMV infection of cassava can be achieved with high efficacy by expressing antisense RNAs against viral mRNAs encoding essential non-structural proteins, providing a new tool to combat CMD in Africa. [source]

    Identification of a defective molecule derived from DNA-A of the bipartite begomovirus of East African cassava mosaic virus

    PLANT PATHOLOGY, Issue 1 2006
    J. Ndunguru
    Geminivirus defective interfering DNAs arise spontaneously in mechanically inoculated test plants, and have previously been found with DNA-B of the bipartite cassava mosaic geminiviruses, but not DNA-A. Reported here for the first time is the cloning and characterization of a naturally occurring truncated form of cassava mosaic geminivirus DNA-A, which at 1525 nt is around half the expected full size. Sequence analysis has shown it to be a defective (df) form of East African cassava mosaic virus (EACMV) DNA-A that has retained its cis elements essential for replication by the helper virus, and it has been termed df DNA-A 15. Phylogenetic comparisons placed the df DNA-A 15 molecule close to mild and severe isolates of EACMV-UG2. Biolistic inoculation of Nicotiana benthamiana with infectious df DNA-A 15 clone and East African cassava mosaic Cameroon virus (EACMCV) resulted in symptom amelioration as compared with EACMCV singly inoculated plants, and there was an accumulation of df DNA-A 15 in systemically infected leaves. In addition, the level of EACMV DNA-B accumulation was reduced in the coinoculated plants compared with those inoculated with EACMCV alone. PCR and sequence analysis confirmed the helper virus as EACMV. [source]

    Symptom severity of cassava mosaic disease in relation to concentration of African cassava mosaic virus in different cassava genotypes

    PLANT PATHOLOGY, Issue 1 2003
    F. O. Ogbe
    The concentration of African cassava mosaic virus (ACMV) was assessed by enzyme-linked immunosorbent assay in relation to symptom severity among resistant, moderately resistant and susceptible cassava genotypes. Resistant genotype NR 8083 had significantly lower symptom severity scores (P < 0·05) than the susceptible genotype TMS 91934, but the two genotypes contained similar levels of virus concentration. The moderately resistant genotypes TMS 30572 and NR 8082 expressed significantly lower symptom severities (P < 0·05) than the susceptible genotypes TMS 91934 and TME 117, but they contained significantly higher virus concentrations (P < 0·05) than TMS 91934 and similar virus concentration as in TME 117. However, two other resistant genotypes, TME 1 and TME 8, had low symptom severity scores and virus concentrations. There was significant interaction (P , 0·05) between cropping season and virus concentration in all the genotypes except TMS 30572. The resistant and moderately resistant genotypes that had high virus concentrations sustained storage root yield losses. The severity of symptoms expressed was not necessarily a reflection of the virus concentration in some of the genotypes. In addition to the use of symptom severity scores to group genotypes into resistant classes, it is recommended that virus concentration should also be considered. Genotypes displaying mild symptoms, but with high levels of virus accumulation, could be an important source of inoculum in the spread of ACMV by the whitefly vectors. This suggests that each genotype should be tested for virus accumulation prior to its release to the farmers. [source]

    Occurrence of the Uganda variant of East African cassava mosaic virus (EACMV-Ug) in western Democratic Republic of Congo and the Congo Republic defines the westernmost extent of the CMD pandemic in East/Central Africa

    PLANT PATHOLOGY, Issue 3 2002
    P. Neuenschwander
    No abstract is available for this article. [source]

    Occurrence of three distinct begomoviruses in cassava in Madagascar

    ANNALS OF APPLIED BIOLOGY, Issue 3 2002
    S RANOMENJANAHARY
    Summary The presence of East African cassava mosaic virus in association with cassava mosaic disease in Madagascar has previously been reported. We now describe virus isolates from mosaic-affected Madagascan cassava with epitope profiles typical of African cassava mosaic virus, and an isolate with a nucleotide sequence similar to that of South African cassava mosaic virus. Thus, three distinct begomoviruses occur in cassava in Madagascar. [source]