Genetic Regulation and Impacts of Acylsugar Chemotype in Tomato

The wild tomato Solanum pennellii exudes acylsugars from glandular trichomes, providing resistance to many insect pest species. Acylsugars consist of a sucrose or glucose moiety esterified to three fatty acids of variable lengths and branching patterns. Transfer of acylsugar production from S. pennellii LA716, which produces acylglucoses with primarily i-C4, i-C10, and ai-C5 acids, to tomato generated the Cornell benchmark line, CU071026, which contains five S. pennellii introgressions and produces acylsucroses with i-C5, n-C12, and ai-C5 acids.

To examine the genetic regulation of acylsugar chemotype, CU071026 was crossed to S. pennellii LA716, and the resulting F1 was backcrossed to CU071026 to produce a BC1F1 population. Three epistatic QTL controlling base moiety were identified on chromosomes 3, 4, and 11 in this BC1F1, and were verified in a BC1F2 population. These three QTL completely shifted acylsugar production from acylsucroses to acylglucoses. Fatty acid QTL on chromosomes 2, 5, and 7 identified in the BC1F1 shifted the precursor, elongation, and extent of elongation of the primary fatty acids, respectively. The chromosome 2 QTL was introgressed into CU071026 and its activity confirmed.

Bioassays of different purified S. pennelliiacylsugars, were performed to inform the breeding of chemotype and indicate that diversity of chemotypes might be important for degree of insect control.

Understanding the genetic regulation of acylsugar chemistry will facilitate breeding tomato lines with optimal acylsugar chemotypes for control of important pest species. The resulting tomato lines will be a valuable tool for sustainable environmentally-sound control of tomato pests.