Effect of cocksfoot mottle virus on resistant and susceptible cocksfoot cultivars grown alone or in combination with healthy or ryegrass mosaic virus‐infected Italian ryegrass

Abstract

S U M M A R YCocksfoot mottle virus (CfMV) was readily transmitted on cutting implements. However, after six harvests, only a quarter as many plants of the resistant cv. Cambria as of the susceptible cv. S.37 became infected. In addition to resistance to becoming infected, cv. Cambria also possessed some resistance once infected, and suffered less mortality than S.37. More CfMV-infected plants died when competing with healthy plants than when competing with other infected plants.Both CfMV and ryegrass mosaic virus (RMV) caused greater reductions in the yield of their respective hosts in mixed stands of cocksfoot and Italian ryegrass than in single species stands. CfMV reduced the proportion of cocksfoot in the mixture and RMV the proportion of ryegrass. However, CfMV-infected cv. Cambria competed better than CfMV-infected cv. S.37 with healthy or with RMV-infected ryegrass.It is concluded that grass cultivars selected for resistance to virus infection will slow down the rate of disease spread within the sward, and selecting for postinfection resistance will help maintain the aggressiveness and competitive ability of plants once they become infected. 0 1987 Association of Applied Biologists

Effect of crown rust on regrowth, competitive ability and nutritional quality of perennial and Italian ryegrasses

“…The debilitating effect of crown rust on competitive ability has been reported by Lancashire & Latch (1970), who found that infected mixed swards of perennial ryegrass and white clover became dominated by clover. Also, Trorey (1979) reported increased yields of cocksfoot when in competition with infected perennial ryegrass Virus infections, too, cause similar changes in ryegrass mixlures and in ryegrass cocksfool swards (Catherall, 1987;Cathcrall & Potter, These effecis on compctiiivc ability may be explained by the differing tillering ability and growth hiibils of cultivars Perennial ryegrass tillers freely and is usually prostrate in growth habit. Therefore, this species will be more strongly competitive on a horizontal than on a vertical plane.…”

“…These effects reduce the competitive ability of infected plants to the advantage of other species (Lancashire & Latch, 1970). Although Catherall (1987) has shown that viruses can drastically afTect the competitive ability of infected components of mixed swards of ryegrasses, there are no detailed reports of effects of crown rust infection on mixtures of susceptible and resistant ryegrass plants.…”

Alteration of plant species mixtures by virus infection: Managed pastures the forgotten dimension

“…Table 1 summarizes the main approach used for each of them, the research question being addressed and their main species balance outcomes. They (Bain et al, 1998;Catherall, 1987;Catherall & Potter, 1987;Ragland et al, 1986);…”

“…Thus, when in competition with a nonhost species, the susceptible, sensitive D. glomerata cultivar S.37 was suppressed to a greater extent than the partially resistant cultivar Cambria. Catherall and Potter (1987) concluded that "in mixed species swards, a virus infection in one species can greatly affect the aggressiveness of each component of the mixture. This will ultimately change the botanical composition of the sward and this in turn will affect the yield and quality of the herbage produced".…”

“…A diverse range of studies have examined fitness parameter modifications that result from virus infection of individual wild plant species (reviewed by Cooper & Jones, 2006;Malmstrom & Alexander, 2016;Power, 2008;and Power et al, 2011). Despite in mixtures of pasture grass species (Bain et al, 1998;Catherall, 1987;Catherall & Potter, 1987), or previous studies where the impact of virus infection was studied in mixtures of grass and legume species (Coutts & Jones, 2002;Jones & Nicholas, 1998;McLaughlin et al, 1992;Ragland et al, 1986). Indeed, the phenomenon of a BYDV-tolerant grass species outcompeting a BYDVsensitive grass species within a grass species mixture had already been described in the literature (Catherall, 1987).…”