A linkage map of the tomato spotted wilt virus resistance gene Sw-5 using near isogenic lines and an interspecific cross

摘要

RFLP analyses were used to position Sw-5, the tomato spotted wilt tospovirus (TSWV) resistance gene derived from Lycopersicon peruvianum, to the long arm of chromosome 9 of tomato (L. esculentum) in the subtelomeric region between CT71 and CT220. Additional codominant RAPD markers linked to Sw-5 were identified. The RAPD originating from the resistant DNA is a 0.94-kbp band, named 421R. This resistant band was linked to CT71 and Sw-5 in a population segregating for Sw-5. These data were confirmed using the original interspecific population L. esculentum X L. pennellii (LA716) used to map Sw-5. Susceptible L. esculentum plants lack the 421R band but contain a 0.90-kbp band not present in resistant plants or in TSWV-susceptible L. pennellii plants.Near isogenic lines (NILs) were developed to aid in the localization of Sw-5. Using a segregating L. esculentum backcross population derived from the NILs the 421R band and Sw-5 were mapped to about 1 cM. Using RFLP analyses on resistant plants from theNIL segregating backcross population, it was determined that CT220 is about 2.4 cM from Sw-5. Using pulse-field gel electrophoresis for restriction mapping of large DNAs determined that a probable crossover event separating L. esculentum from L. peruvianum is between CT71 and Sw-5. The evidence also suggests that CT220 maps within the introgressed L. peruvianum DNA containing Sw-5.