A New Tobamovirus-resistance Gene, L1a, of Sweet Pepper (Capsicum annuum L.)

Tobamoviruses are classified into four pathotypes, P0, P1, P1, 2 and P1, 2, 3, based on the infection patterns in Capsicum plants that carry different L genes, L1-L4. Paprika mild mottle virus Japanese strain (PaMMV-J), a PI pathotype of Tobamovirus, systemically infected L1-homozygote Capsicum plants and induced mosaic on upper uninoculated leaves. The same virus induced systemic necrosis in 19 commercial cultivars and three breeding fixed lines of Capsicum plants resistant and susceptible to the P0 and P1, 2 pathotypes of Tobamovirus, respectively. Genetic analysis showed that resistance to the P0 pathotype of Tobamovirus of these cultivars and fixed lines differed from L1 and depended on a locus, which may be located on or near the L gene locus. Therefore, we designate the new gene as L1a. Both L1a- homozygote and - heterozygote plants showed resistance to the P0 pathotype of Tobamovirus when incubated at 24°C to 30°C, suggesting that resistance of the Lla to P0 pathotype of Tobamovirus is temperature- and gene dosage-independent. Interestingly, L1a-homozygote but not -heterozygote plants are resistant to PaMMV-J when incubated at 24°C but not at 26°C, indicating that L1a plants resistant to PaMMV-J are temperature- and gene dosage-dependent.