Assessment of a generic method for the detection of begomoviruses (BegomoVal)

The genus Begomovirus (Family Geminiviridae) is the largest genus of plant viruses with more than 424 species. In Europe and especially in the Mediterranean basin, several members of this genus have mainly been detected on tomato, but also on others dicotyledonous crops of economic importance.

Early diagnosis of begomoviruses based on symptoms is not reliable as biotic and abiotic factors may induce similar symptoms. Serological tests (ELISA) can also be used, but with limited success due to low antigenicity of the viral coat protein (CP). No diagnostic test is available for the generic detection of begomoviruses. A Diagnostic Protocol for tomato leaf curl virus (TYLCV) and tomato mottle virus (ToMoV) (EPPO PM7/50) is available, but it was not evaluated for other begomoviruses. This project focused on the validation of diagnostic tests in accordance with the EPPO Standard PM7/98 Specific requirements for laboratories preparing accreditation for a plant pest diagnostic activity and was organised in accordance with the EPPO standard PM7/122 Guidelines for the organization of interlaboratory comparisons by plant pest diagnostic laboratories.

Four diagnostic tests were compared: the conventional PCR from Wyatt and Brown (1996) and optimised by the Dutch National Plant Protection Organization (M. Botermans, personal communication), the conventional PCR from Saison and Gentit (2015), the conventional PCR adapted from Li et al. (2004) and the conventional PCR from Accotto et al. (2000) currently included in the EPPO standard PM7/50 tomato yellow leaf curl and tomato mottle begomoviruses. Among the four methods evaluated, the test from Wyatt and Brown (1996) modified and the test from Saison and Gentit (2015) showed the best performances. The tests adapted from Li et al. (2004) and the test from Accotto et al. (2000) did not show good analytical sensitivity and did not allow to detect all isolates included in the test performance study panel.