Quantitative trait loci regulating the fatty acid profile of acylsugars in tomato

Abstract

Acylsugars are secondary metabolites with proven insect resistance properties that are produced by many Solanaceous species including Solanum pennellii, a wild relative of tomato. The acylsugar chemotypes of S. pennellii varies greatly within its natural range and might be the product of plant/insect coevolution. The S. pennellii accession LA716 was used to transfer increased levels of acylsugar production into the cultivated tomato, resulting in the acylsugar tomato breeding line CU071026. S. pennellii accession LA716 produces high levels of acylsugars with chemotypes that differ greatly from those produced by CU071026 or the trace acylsugars of cultivated tomato. Understanding the genetic regulation of acylsugar chemistry will aid efforts to breed acylsugar production into cultivated tomato, allowing for alteration of both acylsugar base moieties and fatty acid profiles. This study uses a BC1F1 population produced from the cross of S. pennellii LA716 and CU071026 with CU071026 as the recurrent parent to identify QTL that change the fatty acid profile of acylsugars. Multiple QTL and epistatic interactions between QTL were detected including three QTL on chromosomes 2, 5, and 7, which significantly alter the percentage of extended iso-odd branched fatty acids and straight chain fatty acids on the acylsugars. We also report the introgression of one of these QTL, FA 2, into CU071026, resulting in a new tomato line with significantly increased i11:0 as a percentage of the fatty acids in its acylsugars. Candidate genes for these QTL and the impacts of altering acylsugar fatty acid are discussed.