The coat protein genes of two field isolates of Lettuce mosaic virus (LMV) from São Paulo State, previously characterized based on their virulence on lettuce (Lactuca sativa) differential cultivars as belonging to pathotypes II (isolate AF198, unable to infect cultivars possessing the genes mo1¹ or mo1²) and IV (isolate AF199, which breaks the resistance conferred by mo1¹ or mo1²), were cloned and sequenced. Comparisons of the nucleotide sequences from European, Middle-Eastern, North American, and the two Brazilian isolates did not distinguish strains, because homologies were always greater than 95%. However, phylogenetic analysis indicated that the Brazilian isolate AF198 clusters with isolates LMV-R and LMV-0 (pathotype II, from the United States and France, respectively). Isolate AF199 clustered with two isolates (LMV-Aud and LMV-13) from France. These isolates are also closely related to isolates from Chile, although a common origin is not proposed. Independent mutation events may be occurring in different parts of the world, leading to the emergence of distinct LMV strains capable of overcoming the resistance genes mo1¹ or mo1².
Lactuca; lettuce; Potyvirus; LMV; capsid protein; cloning; resistance
