The selection of spotted-wilt resistant phenotypes in the potato (Solanum tuberosum)

Abstract

Spotted-wilt-resistant and susceptible phenotypes among potato varieties and hybrids are not determined satisfactorily by hand-inoculation of leaves, but can be selected by stem-tip inoculation of vigorously growing plants at the flowering stage with a strain mixture of the virus. This glasshouse method gives a better differentiation than that obtained in field epidemics. Phloroglucinol staining of infected stems indicated that spotted wilt affects the same tissues as virus Y. Studies on the movement of spotted wilt have shown that varieties like Brownell have a high degree of tolerance, and that the tip blight and necrotic strains of a mixture take part in the early stages of systemic infection in susceptible varieties. A high percentage of the hybrids bred by the authors were resistant to spotted wilt.