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Variability within the pepper-infecting potyviruses Pepper veinal mottle virus (PVMV) and Chili veinal mottle virus (ChiVMV) in Africa and Asia was investigated. Coat protein (CP) gene sequence diversity revealed three clades that corresponded to three geographic locations and there was no evidence of presence of the ChiVMV/Asian group in western or central Africa. These clades included closely related isolates that potentially belong to two viral species, which is consistent with current nomenclature. These clades could not be unambiguously identified with polyclonal antisera; however, reverse transcription-polymerase chain reactions allowed differentiation of the isolates into two species based on a large indel in the CP gene. PVMV and ChiVMV isolates were classified into three and two pathotypes, respectively, in relation to pepper genotypes carrying different resistance factors. Specificity of resistance only partially corresponded to molecular diversity of the isolates. Only one isolate of PVMV could infect pepper genotypes carrying the two recessive genes pvr6 and pvr2 (2); however, these genotypes were not infected by PVMV in field trials in Senegal, despite a high prevalence of PVMV in the surrounding pepper plants.

Tomato chlorosis virus (ToCV) and Tomato infectious chlorosis virus (TICV) are two criniviruses inducing similar yellowing symptoms in tomato. An approximately 4 kb central region of the genomic RNA2 of French ToCV and TICV isolates was sequenced. TICV, for which no other sequences were available, appeared as a distant species in the genus, being close only to LIYV ( Lettuce infectious yellows virus ) for some, but not all, proteins. ToCV has more than 98% nucleotide identity with isolates from the US and Spain, and sequencing the CP gene of several isolates collected in different regions in southern France during 2 years suggested a unique origin. Polyclonal antisera were produced using capsid proteins of both viruses expressed in Escherichia coli . DAS-ELISA assays were developed for routine diagnosis and conditions for preparing samples for an optimized detection were determined. No cross-reactions were observed. However, some false-negative results, corresponding to samples giving ELISA readings close to the detection limit were regularly detected, particularly for ToCV (approximately 5% of the samples). A triplex RT-PCR assay was thus developed, which allowed detection of both viruses in a one-step protocol. An internal PCR control was included, which in addition showed that it could be used as a control for the entire RT-PCR procedure. Finally, combining DAS-ELISA in a first round, and triplex RT-PCR for doubtful samples, appeared the best way to achieve a reliable diagnosis of these viruses.

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Several potyviruses affect lettuce (Lactuca sativa) and chicory (Cichorium spp.) crops worldwide and are important constraints for production because of the direct losses that they induce and/or because of their seed transmission. Here, the molecular and biological properties are described of two potyviruses that were recently isolated from lettuce plants showing mosaic or strong necrotic symptoms in an experimental field in southeastern France. The first potyvirus belongs to the species Endive necrotic mosaic virus and is present in a large number of wild plant species, especially Tragopogon pratensis. It is unable to infect lettuce cultivars with a resistance to Turnip mosaic virus that is present in many European cultivars and probably conferred by the Tu gene. The second potyvirus belongs to the tentative species lettuce Italian necrotic virus and was not observed in wild plants. It infected all tested lettuce cultivars. Wild accessions of Lactuca serriola, Lactuca saligna, Lactuca virosa and Lactuca perennis were identified as resistant to one or the other potyvirus and could be used for resistance breeding in lettuce. No resistance against these two potyviruses was observed in the tested Cichorium endivia cultivars. In contrast, all tested Cichorium intybus cultivars or accessions were resistant.