Abstract
The Colorado potato beetle (CPB; Leptinotarsa decemlineata Say), the most economically important insect pest on potato (Solanum tuberosum L.), also feeds on other Solanaceae, including cultivated tomato (Solanum lycopersicum L.). We used tomato genetic mapping populations to investigate natural variation in CPB resistance. CPB bioassays with 74 tomato lines carrying introgressions of Solanum pennellii in S. lycopersicum cv. M82 identified introgressions from S. pennellii on chromosomes 1 and 6 conferring CPB susceptibility, whereas introgressions on chromosomes 1, 8 and 10 conferred higher resistance. Mapping of CPB resistance using 113 recombinant inbred lines derived from a cross between S. lycopersicum cv UC-204B and Solanum galapagense identified significant quantitative trait loci on chromosomes 6 and 8. In each case, the S. galapagense alleles were associated with lower leaf damage and reduced larval growth. Results of both genetic mapping approaches converged on the same region of chromosome 6, which may have important functions in tomato defense against CPB herbivory. Although genetic mapping identified quantitative trait loci encompassing known genes for tomato acyl sugar and glycoalkaloid biosynthesis, experiments with acyl sugar near-isogenic lines and transgenic GAME9 glycoalkaloid-deficient and overproducing lines showed no significant effect of these otherwise insect-defensive metabolites on CPB performance.
Highlights
The Colorado potato beetle (CPB, Leptinotarsa decemlineata Say) has become the most important insect pest on cultivated potato (Solanum tuberosum L.)
M82 × S. pennellii LA0716 introgression lines, as well as in recombinant inbred lines (RILs) derived from S. lycopersicum cultivar UC-204B × S. galapagense LA048322,29, with the objective being the genetic mapping of quantitative trait loci (QTL) that provide CPB resistance
As differences in CPB performance on S. pennellii introgression lines were greater after 10 days of plant growth than on younger seedlings, this growth stage was used to investigate the genetic basis of tomato defense against CPB
Summary
The Colorado potato beetle (CPB, Leptinotarsa decemlineata Say) has become the most important insect pest on cultivated potato (Solanum tuberosum L.). Both adult beetles and larvae feed on potato leaves. The S. pennellii introgression population, which was developed to study the genetic components of tomato yield and fruit quality, has been widely used for mapping other important quantitative trait loci (QTL) related to biotic and abiotic stress responses. M82 × S. pennellii LA0716 introgression lines, as well as in RILs derived from S. lycopersicum cultivar UC-204B × S. galapagense LA048322,29, with the objective being the genetic mapping of QTLs that provide CPB resistance
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