The prevalence and spatial distribution of viruses in natural populations of Brassica oleracea

Abstract

We report a survey of four viruses (beet western yellows luteovirus (BWYV), cauliflower mosaic caulimovirus (CaMV), turnip mosaic potyvirus (TuMV), turnip yellow mosaic tymovirus (TYMV)) in five natural populations of Brassica oleracea in Dorset (UK). All four viruses were common ; 43% of plants were infected with BWYV, 60% with CaMV, 43% with TuMV and 18% with TYMV. For each virus there were significant differences in the proportion of infected plants among populations, which were not completely explained by differences in the age of plants. Multiple virus infections were prevalent, with 54% of plants having two or more virus types. There were statistically significant associations between pairs of viruses. The CaMV was positively associated with the other three viruses, and BWYV was also positively associated with TuMV. There was no detectable association between BWYV and TYMV, whereas TuMV and TYMV were negatively associated. We suggest these associations result from BWYV, CaMV and TuMV having aphid vectors in common, as aphids are attracted to plants that already have a virus infection. Infected plants were distributed randomly or were very weakly aggregated within populations. The implications of widespread multiple virus infections in natural plant populations are discussed with respect to the release of transgenic plants expressing virus-derived genes.

How Virulent Should a Parasite Be to Its Vector?

“…However, one recent study has shown competitive displacement of fungal pathogen strains in locusts (Thomas et al 2003), and it would be valuable to determine the degree to which this occurs in invertebrate pathogens that fit the model of vector-borne disease. Competitive displacement has also been found in plants, as well as multiple infections of plant and insect hosts or patches (Power 1996, 2000, Raybould et al 1999. However, with only the insects dispersing parasites, parasite competitiveness is the least sensitive of the parameters in the model (Fig.…”

“…We have dealt with superinfection as this is mathematically more tractable than multiple infection, but both represent the degree to which a parasite controls the host in the face of competition. There have been efforts to assess multiple infection of individuals or patches in the field (Lam and Marshall 1968, Power 1996, Raybould et al 1999, Armstrong and Rico-Hesse 2001. For invertebrate diseases, it may be too early to apply our predictions to individual systems given the lack of empirical data on parasite competition.…”

Comparative fitness of a wild squash species and three generations of hybrids between wild×virus-resistant transgenic squash

“…One of the major environmental safety issues over transgenic crops relates to the consequences of gene flow into wild relatives in regard to increased fitness and enhanced weediness (Dale, 1992;Hancock et al, 1996;Kareiva et al, 1994;Raybould, 1999;Rissler and Mellon, 1996;Snow and Palma, 1997). Indeed, genetically engineered crops, as well as conventionally bred crops, have the potential to spontaneously hybridize with their sexually compatible wild, i.e.…”

Survey of Viruses Present in Radish Fields in 2014

“…TuMV Potyviridae ( , family) Potyvirus ( , genus) . 300 89 (Raybould , 1999;Sánchez , 2003). Bromoviridae ( , family) Cucumovirus ( , genus) CMV ,…”