ANALYSIS OF THE VARIABILITY OF TUNISIAN ISOLATES OF LETTUCE MOSAIC VIRUS USING BIOLOGICAL AND MOLECULAR PROPERTIES
H. Fakhfakh, O. Le Gall, T. Candresse, M. Marrakchi
Lettuce mosaic virus (LMV) can be very destructive on lettuce crops as, a very high proportion of infected plants may result from a low level of infected seeds. In addition, LMV isolates able to overcome the mo11 and mo12 resistance genes classically deployed by breeders to protect lettuce crops have now been reported from several countries. In order to gain an understanding of the variability present among LMV populations in Tunisia, nine LMV isolates from lettuce fields were submitted to biological and molecular analysis. Phenotypically, two isolates were able to overcome the resistance gene mo11 of lettuce cv. ‘Mantilia’. At the molecular level, the RT-PCR technique, coupled with RFLP analysis or direct sequencing were used to study a short, hypervariable region of the LMV genome. Restriction patterns and sequence comparison with isolates representative of different pathotypes and/or geographic origins showed that Tunisian LMV isolates are related to other western European isolates, stressing the problem of exchanges of contaminated seed lots.