Effects of High-Level Acylsugar-Producing Tomato Lines on the Development of Tomato Psyllids (Hemiptera: Triozidae).

Acylsugars have been shown to provide activity against numerous insect pests of tomatoes. Comparison of acylsugar levels in four tomato plant lines, FA7/AS, FA2/AS, CU071026, and 'Yellow Pear', found that the acylsugar contents in the elevated acylsugar lines were significantly higher than the commercial Yellow Pear (control) tomato plant line. Adult choice tests indicated that the tomato psyllid, Bactericera cockerelli, preferred to settle on the Yellow Pear and FA2/AS lines over the line with the highest content of acylsugars, FA7/AS, and the parental line, CU071026. The no-choice test demonstrated that adults laid fewer eggs on the high acylsugar tomato lines than on the control tomato line, Yellow Pear. For all high acylsugar lines, the relative growth index of the psyllid was significantly lower compared with the commercial line, indicating a reduced potential for population growth. Although some tomato psyllids completed their life cycle on the high acylsugar tomato plant lines, the percent survival of psyllids to the adult stage when developing on the high acylsugar lines was significantly less (range = 43.7-57.1%) than on the commercial tomato line (83.8%). All mortality occurred during the early stages of development (egg stage to third instar), which has implications for acquisition and transmission of Candidatus Liberibacter solanacearum, the causal agent of tomato vein greening disease. Therefore, with reduced attractiveness for tomato psyllids and significantly reduced survival, the high-acylsugar tomato plant lines have the potential to be part of an integrated pest management program for this pest

A thrips vector of tomato spotted wilt virus responds to tomato acylsugar chemical diversity with reduced oviposition and virus inoculation.

There is increasing evidence that acylsugars deter insect pests and plant virus vectors, including the western flower thrips (WFT), Frankliniella occidentalis (Pergande), vector of tomato spotted wilt virus (TSWV). Acylsugars are sugar-polyesters composed of saturated, un-saturated, and variously branched short and long chain fatty acids (FAs) esterified to a glucose (acylglucose) or sucrose (acylsucrose) moiety. We sought to understand how acylsucrose amount and composition of associated FA profiles interacted to mediate resistance to WFT oviposition and TSWV inoculation on tomato leaves. Towards this goal, we examined WFT oviposition and TSWV inoculation behavior on tomato lines bred to exude varying amounts of acylsucrose in association with diverse FA profiles. Our data show that as acylsucrose amounts increased, WFT egg-laying (oviposition) decreased and TSWV inoculation was suppressed. Western flower thrips also responded to FA profiles that included iC4, iC11, nC12 and nC10 FA. These findings support improving acylsugar-mediated resistance against WFT by breeding tomatoes exuding greater amounts of acylsucrose associated with specific FA profiles. We show that increasing acylsucrose amount output by type IV trichomes and selecting for particular FA profiles through advanced breeding profoundly affects WFT behavior in ways that benefit management of WFT as direct pests and as TSWV vectors

Pedigrees or category of all entries included in field trials.

Pedigrees or category of all entries included in field trials.</p

Hierarchical clustering of included tomato entries by relative abundance of acylsugar fatty acids, where each fatty acid constitutes a percentage of the total fatty acid profile for a given entry.

Fatty acids included make up at least 1 percent of a given entries’ total fatty acid profile. Pearson correlation used to separate entries. Within a row, colors are standardized across columns, allowing comparisons of the relative proportion of an individual fatty acid across entries, but does not reveal the absolute amount of the acylsugar fatty acids (see S3 Fig for this information). Comparisons within a column are not relevant, because the colors do not convey relative proportion of each fatty acid within an entry (see S2 Fig for this information). Color represents the relative abundance of an acylsugar fatty acid for a given entry with red indicating higher accumulation compared to the other entries in the row, and blue indicating a lower relative percent accumulation of a fatty acid compared to the other entries. Purple represents fatty acids that could not be detected for a given entry. Entries with the prefix "FA" have modified fatty acid profiles and entries with the prefix "ISX" are interspecific hybrids with modified fatty acid profiles; these two groups displayed the most unique fatty acid profiles and clustering patterns.</p

Least square mean estimates of the number of whitefly nymphs (± SEM) from 10 leaflet counts averaged across field trials/seasons.

Abundance of eggs was analyzed as a log-normally distributed variable. Entries not connected by the same letter are significantly different (a = 0.05) Tukey HSD.</p

Acylsugar backbone profile of entries.

Total accumulation amount of acylsugars of each entry averaged across samples and experiments. Acylsugars were determined to have either a sucrose (acylsucrose) or glucose (acylglucose) backbone. (TIF)</p

Least square mean estimates of the number of whitefly eggs (± SEM) from 10 leaflet counts averaged across field trials/seasons.

Abundance of eggs was analyzed as a log-normally distributed variable. Entries not connected by the same letter are significantly different (a = 0.05) Tukey HSD.</p

AIC independent variables selected to model abundance of whitefly eggs.

AIC independent variables selected to model abundance of whitefly eggs.</p