Abstract
Four allelic genes, L1, L2, L3 and L4, in Capsicum plants are categorized according to their increasing effectiveness against four respective tobamoviruses. L-mediated virus resistance loses its function when plants are cultivated in an environment over 30°C. Moreover, field cultivation of plants with an incorporated L gene has led to the detection of new tobamoviruses and strains that can overcome virus resistance. In a previous study, we identified a new L gene, L1a. L1a-homozygous plants showed resistance to not only P0 pathotype of Tobamovirus (P0) at any temperature but also Paprika mild mottle virus Japanese strain (PaMMV-J, P1) at 24°C. To develop an efficacious control system for Tobamovirus disease, we characterized the resistance of Capsicum annuum L. ‘Nanbu-Ohnaga’ and identified a new Tobamovirus-resistance gene that differed from L. ‘Nanbu-Ohnaga’ plants showed resistance to PaMMV-J at 30°C but not at 24°C, but they could be systemically infected not only with Tobacco mosaic virus-OM (TMV-OM, P0) and Pepper mild mottle virus Japanese strain (PMMoV-J, P1,2), but also with Tobacco mosaic virus-Ob (TMV-Ob, P1) at any temperature. Genetic analysis of F1, F2, and reciprocal BC1 progenies, derived from a cross between ‘Nanbu-Ohnaga’ and TMVR4-1, a breeding line with the L1a gene in the homozygous state, was established. The data show that the resistance of ‘Nanbu-Ohnaga’ plants to PaMMV-J depends on a single incomplete dominant gene, which differs from the L gene. Hence, this new gene that is designated Hk, is a newly discovered Tobamovirus-resistance gene, which differs from the L gene, in Capsicum plants.
