A New Tobamovirus-resistance Gene, L^1a, of Sweet Pepper (Capsicum annuum L.)

Abstract

Tobamoviruses are classified into four pathotypes, P₀, P₁, P_{1, 2} and P_{1, 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 P_{1, 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 L^1a. Both L^1a- 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, L^1a-homozygote but not -heterozygote plants are resistant to PaMMV-J when incubated at 24°C but not at 26°C, indicating that L^1a plants resistant to PaMMV-J are temperature- and gene dosage-dependent.