Résumé
A standardized single-stranded conformational polymorphism (SSCP) procedure is proposed as an alternative to the timeconsuming biological characterization of Barley yellow dwarf virus-PAV (BYDV-PAV) isolates. Using this procedure, six of 21 overlapping regions used to scan the viral genome gave patterns specific to ‘4E’ (avirulent) or ‘4T’ (‘4E’-derived virulent) isolates. The calibration of samples and integration of SSCP patterns corresponding to the nucleotide region 1482–2023 allowed the estimation of PT values that reflect the proportions of a ‘4T’- specific band. Analysis of the biological (area under the pathogen progress curve) and molecular (PT) data suggested a positive linear relation between these variables. Moreover, sequence analysis of the nucleotide region 1482–2023 highlighted the presence of a nucleotide polymorphism (C/A1835) which can be considered as a candidate for virus–host interactions linked to the monitored virulence. According to these parameters, PT values associated with ‘4E’- and ‘4T’-derived populations show that: (i) long-term infection of a BYDV-PAV isolate on the ‘TC14’ resistant host leads to the fixation of virulent individuals in viral populations; and (ii) the introduction of susceptible hosts in successive ‘TC14’ infections results in the maintenance of low virulence of the populations. Thus, the presented study demonstrates that SSCP is a useful tool for monitoring viral populations during the host adaptation process. The described impact of host alternation provides new opportunities for the use of the ‘TC14’ resistance source in BYDV-resistant breeding programmes. This study is part of the global effort made by the scientific community to propose sustainable alternatives to the chemical control of this viral disease.