Two fully replicated trials were conducted with glasshouse-grown tomatoes, under conditions similar to commercial production, to define the impact of Pepino mosaic virus (PepMV). PepMV was not found to reduce bulk yields in these trials, but the quality of tomato fruits harvested was reduced significantly. Compared with uninoculated, PepMV-free control plants, 6·5% of fruits of PepMV-affected cv. Espero were downgraded from class 1 in trial 1. In trial 2, an average 38% of class 1 fruits from PepMV-affected cvs Espero and Encore were lost as a result of downgrading. Loss of quality was mainly a result of blotchy ripening, gold marbling, gold spot, and symptoms directly attributed to PepMV infection. PepMV infection also affected fruit size. The results are discussed in relation to the demands of multiple retailers in the UK for class 1 tomatoes only.

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Bean common mosaic virus (BCMV) isolates were collected from crops of Phaseolus vulgaris (bean) and from wild legume species in 13 African countries. Isolates of pathotype VIa from both beans and wild legume species were predominant in central, eastern and southern Africa. Isolates of pathotypes I, III, IVa, IVb and Va were also found. Some isolates did not conform to previously published pathotypes, and therefore represent records of novel pathotypes. The susceptibility of various wild legume species to BCMV was investigated and isolates of the virus obtained from Crotalaria incana, Rhynchosia sp., Macroptilium atropurpureum and Cassia occidentalis (synonym Senna occidentalis) were aphid‐transmitted both from P. vulgaris to their original host species and to P. vulgaris. Isolates of BCMV from wild legume species were seed‐transmitted in bean and in several other legume species. The natural occurrence of BCMV in wild legume species in Africa is probably a significant factor in the ecology and epidemiology of the virus and possibly the evolution of isolates of the ‘A’ serotype which induce necrotic reactions in cultivars carrying the I gene for resistance. The occurrence of viruses other than BCMV from P. vulgaris and other legume hosts is also reported. The gene‐for‐gene model described by Drijfhout (1978) is reinterpreted to explain the variation for pathogenicity, and it is proposed that there may be genes which control the temperature sensitivity of necrosis in combination with the I gene.

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The Bemisia tabaci (Gennadius) biotype B transmitted host range of Tomato chlorosis virus (ToCV), genus Crinivirus, Family Closteroviridae, and Cucumber vein yellowing virus (CVYV), genus Ipomovirus, Family Potyviridae, was studied. New experimental hosts were identified for each of these viruses. Seventeen species in eight plant families were assessed as potential hosts for ToCV. Infection in asymptomatic Anthriscus cereifolium (chervil) test plants by ToCV was confirmed by using a Real-Time PCR assay designed for ToCV. The presence of readily transmissible, infectious ToCV virions in A. cereifolium was confirmed by re-isolation of the virus via whitefly-transmission from A. cereifolium to Lycopersicon esculentum and A. cereifolium. This is the first report of the experimental transmission of ToCV by B. tabaci to a species within the Umbelliferae. All other hosts assessed for the presence of ToCV were found to be uninfected. Ten species in five families were assessed as potential hosts for CVYV. The CVYV host range identified included some important crops and common weeds, such as L. esculentum, Nicotiana tabacum, A. cereifolium, Datura stramonium, Nicotiana benthamiana, Nicotiana clevlandii and Cucumis sativus. Symptoms were present on D. stramonium, N. benthamiana and C. sativus control plants. The presence of infectious whitefly transmitted CVYV virions was confirmed solely for D. stramonium and N. tabacum, following re-isolation of the virus via B. tabaci transmission from all infected species to C. sativus. This is the first report of experimental CVYV transmission by B. tabaci to non-cucurbitaceous crop and weed hosts belonging to the Solanaceae or Umbelliferae.