Transmission properties of Iranian wheat stripe virus

Transmission properties of Iranian wheat stripe virus (IWSV), a tentative member of the genus Tenuivirus, were studied. Results showed that similar to other tenuiviruses, IWSV multiplies in its vector, Unkanodes tanasijevici. In bioassay experiments, IWSV transmission rate by individual U. tanasijevici showed an increase with time after acquisition. IWSV was transovarially transmitted to 88-100% of progeny. The nymphs continued to be infective in the adult stage but with decreased efficiency. Males and females transmitted the virus with equal efficiency. Transmission properties of IWSV confirm the position of the virus in the genus Tenuivirus.

Economic impact of Turnip mosaic virus, Cauliflower mosaic virus and Beet mosaic virus in three Kenyan vegetables

Screenhouse experiments conducted in Kenya showed that inoculation of cabbage seedlings with Turnip mosaic virus (TuMV), either alone, or in combination with Cauliflower mosaic virus (CaMV), reduced the number and weight of marketable harvested heads. When viruses were inoculated simultaneously, 25% of cabbage heads were non-marketable, representing 20-fold loss compared with control. By contrast, inoculation with CaMV alone had insignificant effects on cabbage yield. This suggests that TuMV is the more detrimental of these pathogens, and its management should be a priority. Early exposure to TuMV produced cabbages that were 50% lighter than non-infected plants, but later infection was less damaging suggesting that controlling virus infection at the seedling stage is more important. TuMV was far less damaging to kale than it was to cabbage; although high proportions of TuMV-inoculated kale plants showed symptoms (> 90%), the marketability and quality of leaves were not significantly reduced, and no clear relationship existed between timing of infection and subsequent crop losses. Early inoculation of Swiss chard with Beet mosaic virus (BtMV) significantly impaired leaf quality (similar to 50% reduction in marketable leaf production), but the impact of disease was greatest in plants that had been inoculated at maturity, where average leaf losses were two and a half times those recorded in virus-free plants. Disease-management of BtMV in Swiss chard is important, therefore, not only at the seedling stage, but particularly when plants are transplanted from nursery to field.

Transmission properties of Iranian wheat stripe virus

Transmission properties of Iranian wheat stripe virus (IWSV), a tentative member of the genus Tenuivirus, were studied. Results showed that similar to other tenuiviruses, IWSV multiplies in its vector, Unkanodes tanasijevici. In bioassay experiments, IWSV transmission rate by individual U. tanasijevici showed an increase with time after acquisition. IWSV was transovarially transmitted to 88-100% of progeny. The nymphs continued to be infective in the adult stage but with decreased efficiency. Males and females transmitted the virus with equal efficiency. Transmission properties of IWSV confirm the position of the virus in the genus Tenuivirus.

Investigation on Cacao swollen shoot virus (CSSV) pollen transmission through cross-pollination

DNA- and RNA-based polymerase chain reaction (PCR) systems were used with Cacao swollen shoot virus (CSSV) primers designed from conserved regions of the six published genomic sequences of CSSV to investigate whether the virus is transmissible from infected trees through cross-pollination to seeds and seedlings. Pollen was harvested from CSSV infected cocoa trees and used to cross-pollinate flowers of healthy cocoa trees (recipient parents) to generate enough cocoa seeds for the PCR screening. Adequate precautions were taken to avoid cross-contamination during duplicated DNA extractions and only PCR results accompanied by effective positive and negative controls were scored. Results from the PCR analyses showed that samples of cocoa pod husk, mesocarp and seed tissues (testa, cotyledon and embryo) from the cross-pollinations were PCR negative for CSSV DNA. Sequential DNA samples from new leaves of seedlings resulting from the cross-pollinated trees were consistently PCR negative for presence of portions of CSSV DNA for over 36 months after germination. A reverse transcription-PCR analysis performed on the seedlings showed negative results, indicating absence of functional CSSV RNA transcripts in the seedlings. None of the seedlings exhibited symptoms characteristic of the CSSV disease, and all infectivity tests on the seedlings were also negative. Following these results, the study concluded that although CSSV DNA was detected in pollen from CSSV infected trees, there was no evidence of pollen transmission of the virus through cross-pollination from infected cocoa parents to healthy cocoa trees. Keywords:badnavirus;CSSV;PCR;pollen;seed transmission;Theobroma cacao

Investigation on Cacao swollen shoot virus (CSSV) pollen transmission through cross-pollination

DNA- and RNA-based polymerase chain reaction (PCR) systems were used with Cacao swollen shoot virus (CSSV) primers designed from conserved regions of the six published genomic sequences of CSSV to investigate whether the virus is transmissible from infected trees through cross-pollination to seeds and seedlings. Pollen was harvested from CSSV infected cocoa trees and used to cross-pollinate flowers of healthy cocoa trees (recipient parents) to generate enough cocoa seeds for the PCR screening. Adequate precautions were taken to avoid cross-contamination during duplicated DNA extractions and only PCR results accompanied by effective positive and negative controls were scored. Results from the PCR analyses showed that samples of cocoa pod husk, mesocarp and seed tissues (testa, cotyledon and embryo) from the cross-pollinations were PCR negative for CSSV DNA. Sequential DNA samples from new leaves of seedlings resulting from the cross-pollinated trees were consistently PCR negative for presence of portions of CSSV DNA for over 36 months after germination. A reverse transcription-PCR analysis performed on the seedlings showed negative results, indicating absence of functional CSSV RNA transcripts in the seedlings. None of the seedlings exhibited symptoms characteristic of the CSSV disease, and all infectivity tests on the seedlings were also negative. Following these results, the study concluded that although CSSV DNA was detected in pollen from CSSV infected trees, there was no evidence of pollen transmission of the virus through cross-pollination from infected cocoa parents to healthy cocoa trees.