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

Stressor- and Corticotropin releasing Factor-induced Reinstatement and Active Stress-related Behavioral Responses are Augmented Following Long-access Cocaine Self-administration by Rats

Rationale Stressful events during periods of drug abstinence likely contribute to relapse in cocaine-dependent individuals. Excessive cocaine use may increase susceptibility to stressor-induced relapse through alterations in brain corticotropin-releasing factor (CRF) responsiveness. Objectives This study examined stressor- and CRF-induced cocaine seeking and other stress-related behaviors in rats with different histories of cocaine self-administration (SA). Materials and methods Rats self-administered cocaine under short-access (ShA; 2 h daily) or long-access (LgA; 6 h daily) conditions for 14 days or were provided access to saline and were tested for reinstatement by a stressor (electric footshock), cocaine or an icv injection of CRF and for behavioral responsiveness on the elevated plus maze, in a novel environment and in the light–dark box after a 14- to 17-day extinction/withdrawal period. Results LgA rats showed escalating patterns of cocaine SA and were more susceptible to reinstatement by cocaine, EFS, or icv CRF than ShA rats. Overall, cocaine SA increased activity in the center field of a novel environment, on the open arms of the elevated plus maze, and in the light compartment of a light–dark box. In most cases, the effects of cocaine SA were dependent on the pattern/amount of cocaine intake with statistically significant differences from saline self-administering controls only observed in LgA rats. Conclusions When examined after several weeks of extinction/ withdrawal, cocaine SA promotes a more active pattern of behavior during times of stress that is associated with a heightened susceptibility to stressor-induced cocaine-seeking behavior and may be the consequence of augmented CRF regulation of addiction-related neurocircuitry

High-Density SNP Genotyping of Tomato (Solanum lycopersicum L.) Reveals Patterns of Genetic Variation Due to Breeding

The effects of selection on genome variation were investigated and visualized in tomato using a high-density single nucleotide polymorphism (SNP) array. 7,720 SNPs were genotyped on a collection of 426 tomato accessions (410 inbreds and 16 hybrids) and over 97% of the markers were polymorphic in the entire collection. Principal component analysis (PCA) and pairwise estimates of F-st supported that the inbred accessions represented seven sub-populations including processing, large-fruited fresh market, large-fruited vintage, cultivated cherry, landrace, wild cherry, and S. pimpinellifolium. Further divisions were found within both the contemporary processing and fresh market sub-populations. These sub-populations showed higher levels of genetic diversity relative to the vintage sub-population. The array provided a large number of polymorphic SNP markers across each sub-population, ranging from 3,159 in the vintage accessions to 6,234 in the cultivated cherry accessions. Visualization of minor allele frequency revealed regions of the genome that distinguished three representative sub-populations of cultivated tomato (processing, fresh market, and vintage), particularly on chromosomes 2, 4, 5, 6, and 11. The PCA loadings and F-st outlier analysis between these three sub-populations identified a large number of candidate loci under positive selection on chromosomes 4, 5, and 11. The extent of linkage disequilibrium (LD) was examined within each chromosome for these sub-populations. LD decay varied between chromosomes and sub-populations, with large differences reflective of breeding history. For example, on chromosome 11, decay occurred over 0.8 cM for processing accessions and over 19.7 cM for fresh market accessions. The observed SNP variation and LD decay suggest that different patterns of genetic variation in cultivated tomato are due to introgression from wild species and selection for market specialization

Evaluating Acylsugars-Mediated Resistance in Tomato against Bemisia tabaci and Transmission of Tomato Yellow Leaf Curl Virus

The sweetpotato whitefly, Bemisia tabaci, is a major pest of cultivated tomato. Whitefly feeding-related injuries and transmission of viruses including tomato yellow leaf curl virus (TYLCV) cause serious losses. Management strategy includes planting resistant cultivars/hybrids. However, TYLCV resistance is incomplete and whiteflies on TYLCV-resistant cultivars/hybrids are managed by insecticides. Acylsugars’-mediated resistance against whiteflies has been introgressed from wild solanums into cultivated tomato. This study evaluated acylsugar-producing tomato lines with quantitative trait loci (QTL) containing introgressions from Solanum pennellii LA716, known to alter acylsugars’ levels or chemistry. Evaluated acylsugar-producing lines were the benchmark line CU071026, QTL6/CU071026—a CU071026 sister line with QTL6, and three other CU071026 sister lines with varying QTLs—FA2/CU71026, FA7/CU071026, and FA2/FA7/CU071026. Non-acylsugar tomato hybrid Florida 47 (FL47) was also evaluated. Acylsugars’ amounts in FA7/CU071026 and FA2/FA7/CU071026 were 1.4 to 2.2 times greater than in other acylsugar-producing lines. Short chain fatty acid, i-C5, was dominant in all acylsugar-producing lines. Long chain fatty acids, n-C10 and n-C12, were more abundant in FA7/CU071026 and FA2/FA7/CU071026 than in other acylsugar-producing lines. Whiteflies preferentially settled on non-acylsugar hybrid FL47 leaves over three out of five acylsugar-producing lines, and whiteflies settled 5 to 85 times more on abaxial than adaxial leaf surface of FL47 than on acylsugar-producing lines. Whiteflies’ survival was 1.5 to 1.9 times lower on acylsugar-producing lines than in FL47. Nevertheless, whiteflies’ developmental time was up to 12.5% shorter on acylsugar-producing lines than on FL47. TYLCV infection following whitefly-mediated transmission to acylsugar-producing lines was 1.4 to 2.8 times lower than FL47, and TYLCV acquisition by whiteflies from acylsugar-producing lines was up to 77% lower than from FL47. However, TYLCV accumulation in acylsugar-producing lines following infection and TYLCV loads in whiteflies upon acquisition from acylsugar-producing lines were not different from FL47. Combining TYLCV resistance with acylsugars’-mediated whitefly resistance in cultivated tomato could substantially benefit whiteflies and TYLCV management

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

Acylsugar amount and fatty acid profile differentially suppress oviposition by western flower thrips, Frankliniella occidentalis, on tomato and interspecific hybrid flowers

Tomatoes (Solanum lycopersicum L.) have been bred to exude higher amounts or different types of the specialized plant metabolites, acylsugars, from type IV trichomes. Acylsugars are known to deter several herbivorous insect pests, including the western flower thrips (WFT), Frankliniella occidentalis (Pergande); however, all previous studies investigated the effect of acylsugars on leaves, or acylsugar extracts obtained from leaves. In spite of the WFT predilection for flowers, there is a gap in knowledge about flower defenses against thrips damage. This is especially important in light of their capacity to acquire and inoculate viruses in the genus Orthotospovirus, such as Tomato spotted wilt orthotospovirus (TSWV), in flowers. Therefore, we turned our attention to assessing thrips oviposition differences on flowers of 14 entries, including 8 interspecific hybrids, 5 tomato lines bred for specific acylsugar-related characteristics (type IV trichome densities, acylsugar amount, sugar moiety and fatty acid profile), and a fresh market tomato hybrid, Mt. Spring, which only produces trace amounts of acylsugars. Our results show that the density of the acylsugar droplet bearing type IV trichomes is greatest on sepals, relative to other flower structures, and accordingly, WFT avoids oviposition on sepals in favor of trichome-sparse petals. In concordance with past studies, acylsugar amount was the most important acylsugar-related characteristic suppressing WFT oviposition. Certain acylsugar fatty acids, specifically i-C5, i-C9 and i-C11, were also significantly associated with changes in WFT oviposition. These results support continued breeding efforts to increase acylsugar amounts and explore modifications of fatty acid profile and their roles in deterring thrips oviposition. The finding that acylsugar production occurs and reduces thrips oviposition in tomato flowers will be important in efforts to use acylsugar-mediated resistance to reduce incidence of orthotospoviruses such as TSWV in tomato by deterring virus transmission and development of thrips vector populations in the crop

Acylsugar amount and fatty acid profile differentially suppress oviposition by western flower thrips, <i>Frankliniella occidentalis</i>, on tomato and interspecific hybrid flowers

<div><p>Tomatoes (<i>Solanum lycopersicum</i> L.) have been bred to exude higher amounts or different types of the specialized plant metabolites, acylsugars, from type IV trichomes. Acylsugars are known to deter several herbivorous insect pests, including the western flower thrips (WFT), <i>Frankliniella occidentalis</i> (Pergande); however, all previous studies investigated the effect of acylsugars on leaves, or acylsugar extracts obtained from leaves. In spite of the WFT predilection for flowers, there is a gap in knowledge about flower defenses against thrips damage. This is especially important in light of their capacity to acquire and inoculate viruses in the genus <i>Orthotospovirus</i>, such as <i>Tomato spotted wilt orthotospovirus</i> (TSWV), in flowers. Therefore, we turned our attention to assessing thrips oviposition differences on flowers of 14 entries, including 8 interspecific hybrids, 5 tomato lines bred for specific acylsugar-related characteristics (type IV trichome densities, acylsugar amount, sugar moiety and fatty acid profile), and a fresh market tomato hybrid, Mt. Spring, which only produces trace amounts of acylsugars. Our results show that the density of the acylsugar droplet bearing type IV trichomes is greatest on sepals, relative to other flower structures, and accordingly, WFT avoids oviposition on sepals in favor of trichome-sparse petals. In concordance with past studies, acylsugar amount was the most important acylsugar-related characteristic suppressing WFT oviposition. Certain acylsugar fatty acids, specifically i-C5, i-C9 and i-C11, were also significantly associated with changes in WFT oviposition. These results support continued breeding efforts to increase acylsugar amounts and explore modifications of fatty acid profile and their roles in deterring thrips oviposition. The finding that acylsugar production occurs and reduces thrips oviposition in tomato flowers will be important in efforts to use acylsugar-mediated resistance to reduce incidence of orthotospoviruses such as TSWV in tomato by deterring virus transmission and development of thrips vector populations in the crop.</p></div