The coat protein gene of tobamovirus P₀ pathotype is a determinant for activation of temperature-insensitive L ^1a -gene-mediated resistance in Capsicum plants

Tobamovirus resistance in Capsicum plants, which is mediated by L genes (L ¹ , L ² , L ³ or L ⁴ ), is known to be temperature sensitive. However, the L ^1a gene, a newly identified tobamovirus resistance gene that is mapped to the L locus, confers temperature-insensitive resistance against the tobamovirus P₀ pathotype. To identify the viral elicitor that activates the L ^1a -gene-mediated resistance, several chimeric viral genomes were constructed between tobacco mosaic virus-L (P₀ pathotype), paprika mild mottle virus-J (P₁ pathotype) and pepper mild mottle virus-J (P_1,2 pathotype). Infection patterns of these chimeric viruses in L ^1a -harboring plants revealed that the L ^1a -gene-mediated resistance was activated by the CP of a particular pathotype of tobamovirus, like other L-gene-mediated resistances, but the L ^1a -gene-mediated resistance differs from those conferred by other L genes in terms of temperature sensitivity.