High temperature effects on hypersensitive resistance to Tomato Spotted Wilt Tospovirus (TSWV) in pepper (Capsicum chinense Jacq.)

The tomato spotted wilt virus resistance in pepper conferred by the Tsw gene is less stable at 32 °C continuous temperature. Continuous high temperatures for at least nine days lead to systemic spread and necrotic symptoms in plants that are totally resistant at a lower temperature (22 °C). We show that continuous high temperatures destabilize this resistance in young plants, but older inoculated plants rarely develop systemic symptoms. Populations segregating for the Tsw gene showed that heterozygosity at the Tsw locus increased the chance of inoculated seedlings to develop systemic necrotic symptoms. Genetic background was less significantly involved in the thermosensitivity of the resistant response. As a consequence, it would be preferable to grow cultivars homozygous at the Tsw locus in high temperature conditions.