E. Redondo et al., Lettuce mosaic virus pathogenicity determinants in susceptible and tolerant lettuce cultivars map to different regions of the viral genome, MOL PL MICR, 14(6), 2001, pp. 804-810
Full-length infectious cDNA clones were constructed for two isolates (LMV-0
and LMV-E) of Lettuce mosaic virus (LMV), a member of the genus Potyvirus.
These two isolates differ in pathogenicity in susceptible and tolerant-res
istant lettuce cultivars, In susceptible plants, LMV-0 induces mild mosaic
symptoms, whereas LMV-E induces severe stunting, leaf deformation, and a ne
crotic mosaic. In plants carrying either of the two probably allelic recess
ive resistance genes mol(1) or mol(2), LMV-0 is restricted partially to the
inoculated leaves, When a systemic invasion does occur, however, symptoms
fail to develop. LMV-E overcomes the protection afforded by the resistance
genes, resulting in systemic mosaic symptoms. Analysis of the behavior of r
ecombinants constructed between the two virus isolates determined that the
HC-Pro protein of LMV-E causes the severe stunting and necrotic mosaic indu
ced by this isolate in susceptible cultivars, In contrast, the ability to o
vercome mol resistance and induce symptoms in the resistant-tolerant cultiv
ars was mapped to the 3' half of the LMV-E genome, These results indicate t
hat the ability to induce severe symptoms and to overcome the protection af
forded by the recessive genes mol(1) Or mol(2) are independent phenomena.