Source: UNIVERSITY OF KENTUCKY submitted to
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
Funding Source
Reporting Frequency
Accession No.
Grant No.
Project No.
Proposal No.
Multistate No.
Program Code
Project Start Date
Oct 1, 2010
Project End Date
Sep 30, 2015
Grant Year
Project Director
Snyder, JO.
Recipient Organization
LEXINGTON,KY 40526-0001
Performing Department
Non Technical Summary
Modern agriculture has relied on application of pesticides to reduce or prevent damage caused by arthropods and disease. However, rising concerns with the direct and indirect costs of pesticide use have spurred searches for alternative approaches to prevent damage caused by these stresses. Use of cultivars having innate resistance to pests provides one path for reducing pesticide application and, perhaps a more sustainable agriculture. Deployment of resistant cultivars could reduce energy-intensive practices such as the use of petroleum-based pesticides or could allow wider adaptation of the crop. Furthermore, use of genetic-based mechanisms of resistance (host resistance) may lead to safer and more ecologically sound agricultural systems. Genetic transfer of host resistance is conceptually straightforward and requires the ability to recognize the trait in populations of genetic resources or in subsequent generations in which the trait may segregate. This requirement applies whether classical plant breeding methods based on pollination and fertilization or methods of genetic engineering are used to transfer the trait. The more that is known about causal mechanisms of resistance, then usually the more efficient the ability to transfer resistance from one plant to another. The proposed approach will provide specific information about causes of insect resistance in tomato, making the production of insect resistant varieties of tomato easier.
Animal Health Component
Research Effort Categories

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
Goals / Objectives
The primary goal of the proposed research is to foster the genetic improvement of host-plant resistance to arthropods in tomato. This goal will be addressed by characterizing the mite resistance mechanisms present in a particular line of Lycopersicon hirsutum (LA2329) and hybrids of this line with L. esculentum, the cultivated tomato. Specific objectives are to: 1) Obtain backcross and F2 generations of interspecific hybrids originating from LA2329 that demonstrate laminar-based resistance to spider mites; 2) Characterize resistance of resulting hybrids using appropriate bioassays; 3) Evaluate leaf toughness and other leaf characters of these hybrids that may be related to laminar-based resistance; 4) Examine leaf chemistry of these hybrids in detail, using a metabolomics approach; 5) Investigate potential genetic linkages with desired phenotypes by bulked segregation analysis; and 6) Investigate mode of secretion of type IV trichomes on L hirsutum (LA2329) and hybrids with L. esculentum by microscopic methods. The primary activities are the conduct and analysis of experiments. Products of these activities are fostering of existing collaborations with colleagues in China, production of novel germplasm that may be used for tomato improvement, and a better model for understanding the nature of pest resistance present in wild relatives of tomato. Because plant breeders are the primary audience for this research, publication in relevant journals, communication of results with collaborators, and presentations at appropriate scientific meetings will be used for dissemination.
Project Methods
Interspecific hybrid genotypes of interest are generated by traditional backcross methods. Bioassays are critical to the approach, to identify resistant phenotypes among interspecific hybrids. However, a battery of bioassays and particular responses in those bioassays will underpin the identification of the most appropriate phenotypes that possess resistant leaf lamina, in contrast to resistance mediated by trichomes. Additionally, leaf toughness will be measured by physical means. After identification of desired resistant phenotypes, leaves will then be characterized to the fullest extent possible using gas chromatography coupled mass spectroscopy. Such an approach creates massive amounts of data, but methods now exist to both visualize and explore relationships between leaf chemical composition and resistance phenotypes (metabolomics). Subsequently, the genetic basis for leaf resistance will be explored using bulked segregant analysis, and other molecular approaches. Because of the nature of the results which are data intensive, statistical procedures such as principle component analysis and other aggregative methods are required to truly evaluate the results. Evaluation of success will depend partly on the outcome of these statistical analyses, and will also depend on whether the indicated causal factors are consistent with what we know of insect resistance in tomato, and what we know about aspects of plant metabolism and plant resistance generally. Efforts that will be used to change knowledge and actions in the target audience will be communication of results through normal channels, including presentations at scientific meeting, publication in scientific journals, and in discussions with collaborators.

Progress 10/01/10 to 09/30/15

Target Audience:Target audiences reached during this reporting period included tomato breeders, tomato producers, and plant scientists. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?The project provided training for 1 Ph.D. student, and 1 Visiting Professor from the Institute of Vegetable Crops, Jiangsu Academy of Agricultural Sciences/Jiangsu Key Laboratory for Horticultural Crop Genetic Improvement, Nanjing, China How have the results been disseminated to communities of interest?The results have been discussed with other tomato breeders in the U.S., Spain, Brazi and China. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

What was accomplished under these goals? Research activities during the reporting period included evaluation of the composition of trichome secretions, trichome densities and self fruit set on greenhouse-grown BC3F1 plants. The donor parent for this generation had type IV trichome densities and zingiberene concentrations similar to that of the wild LA2329 S. habrochaites progenitor. Of the 50 plants evaluated, all BC3F1 individuals produced zingiberene at concentrations ranging from 20 to 60% of the donor parent. All plants in this generation produced fruit after self-pollination and most had low densities of type IV trichomes. Fruit size ranged from 2 to 6 cm in diameter. Plants having higher zingiberene concentrations seemed to produce fruit somewhat later than those individuals with lower concentrations of zingiberene. Total seed produced from these plants ranged from 100 to 2000 BC3F2 seeds per plant. Progeny of nine BC3F1 individuals representing the lower range of zingiberene concentrations in the BC3F1 were chosen for evaluation in the field during the summer of 2015, because seed from the hybrids having higher concentrations were not as yet available. Approximately 51 plants of each of the nine BC3F2 families were transplanted to the field in mid-May. Plants were set 2 feet apart in-row, on raised beds covered with plastic mulch. Beds were six feet apart. The statistical design was a completely random design with three replications of each family. Fertility, including fertigation and irrigation, followed local Cooperative Extension recommendations. Extensive notes were taken on flowering and fruit set. Concurrently, a sampling procedure which allowed preparation of 200 samples per day for subsequent analysis by automated gas chromatography was developed and then deployed. In late June, the zingiberene, and mono terpene and other compounds were evaluated on each plant by gas chromatography. Mean zingiberene concentration did not differ among families. Presence of zingiberene was dominant, likely controlled by one or a few genes. High concentration of zingiberene was recessive, and concentrations similar to that of the donor parent for the BC3 were present in 1 to 3 individuals per family (2 to 5%). Presence and abundance of monoterpenes segregated in each family. Similar to previous results, there was transgressive segregation for abundance of monoterpenes, with concentrations 5 to 8-fold greater than the recurrent parent. Individuals having no monoterpenes or sesquiterpenes were present in the population. Data for terpene concentrations and trichome evaluations are still being analyzed. Densities of type IV and type VI trichomes were evaluated with the aid of a stereo microscope, and densities of type IV trichomes similar to the donor parent were present on less than 10% of the hybrids. Fruit set occurred on about 70% of the plants in the field. Yield on those plants producing fruit, judged visually, ranged from just a few fruit per plant, to more than 50 fruit per plant. Fruit size was highly variable, ranging from 2 to 6 cm inches in diameter with fruit size skewed toward smaller fruit. Fruit flavor was highly variable, with some plants having fruit with little sugar, acid or tomato flavor, and a few individuals with very good tomato flavor. All plants were determinant, as were the donor and recurrent parents. Degree of determinacy varied widely in the population, as did the degree of branching. Approximately ¼ of the plants were shorter in stature than either the donor or the recurrent parent, with some plants being extremely dwarf (less than 1 foot tall) and with small leaves. Cuttings were taken from most non-dwarf plants that had zingiberene concentrations and type IV trichome densities similar to those of the donor parent. In addition, a few plants having elevated and very low monoterpene concentrations, compared to the recurrent parent, in the presence and absence of zingiberene. These plants were placed in the greenhouse for subsequent evaluation. In related work, micro-RNA (miRNA) profiles ofS. lycopersicumand were revealed by deep sequencing. Sixty-three miRNA families were identified in the two species with 39 families in common. Twenty-four families were species specific. Six miRNA families displayed a divergent expression pattern between the two species. Species-specific, differences in non-conserved miRNAs and divergent expression of conserved miRNAs might be associated with phenotypic variation between the two tomato species. The S. habrochaites accession PI 134417 produces intermediate-chain methyl ketones in its trichome secretions. Four MKs (2-tridecanone, 2-undecanone, 2-dodecanone, 2-pentadecanone) and their mixture were screened for repellency and ability to alter fecundity of spider mites. All MKs repelled spider mites. Spray application of crude leaf extracts prepared in ethanol, average number of eggs/female mite dropped from 0.9 to 0.3 24 h after exposure a 68% reduction, suggesting that crude extracts of certain S. habrochaites accessions may possess anti-arthropod activities, and could be useful as an aid in agriculture.


  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Antonious, G. F., Snyder, J. C. 2015. Repellency and oviposition deterrence of wild tomato leaf extracts to spider mites, Tetranychus urticae Koch. Journal of Environmental Science and Health. Part B, Pesticides, Food Contaminants, and Agricultural Wastes. 50(9):667-673.
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Fan ShanShan, Li QianNan, Guo GuangJun, Gao JianChang, Wang XiaoXuan, Guo YanMei, Snyder, J. C., Du YongChen. 2015. Identification of microRNAs in two species of tomato, Solanum lycopersicum and Solanum habrochaites, by deep sequencing. Journal of Integrative Agriculture. 14(1):42-49.

Progress 10/01/13 to 09/30/14

Target Audience: Primary target audiences include tomato breeders worldwide, and researchers in host-plant resistance to insects. Final beneficiaries will be farmers who produce tomatoes. Changes/Problems: Resistanceto spider mitesin hybrids appear to be very high, making differentiation with spider mite bioassays difficult. Alternatives are being explored. What opportunities for training and professional development has the project provided? During the reporting period, Chai Min, a well known and respected tomato breeder associated with the Beijing Vegetable Research Center, visited the lab and greenhouse for a three-week period. During that time we conducted collaborative research aimed at furthering progress on this project. How have the results been disseminated to communities of interest? Breeders in Spain, Florida, and in China have been briefed on current results. What do you plan to do during the next reporting period to accomplish the goals? Activities during the next reporting period will center on characterization of trichome secretion composition and abundance, trichome densities, and ability to self-pollinate in the BC3 generation and their offspring resulting from self-pollination.

What was accomplished under these goals? During the report period BC2F2 (BC2S1) individuals were extensively evaluated by GC-MS for composition of trichome secretions, ability to set seed after self-pollination, and trichome densities. Oxygen-containing sesquiterpene derivatives that are present in the wild parent of the population are largely absent in the progeny. Presence and abundance of monoterpenes, inherited from the domestic parent, appear to segregate for presence and abundance. In some cases abundance of the monoterpenes exceeded that of the S. lycopersicon parent by three- to five-fold. High type IV trichome density was a recessive character and only a few individuals, progeny of parents possessing type IV trichome had significant type IV trichome densities. Of all the plants examined only one plant having type IV trichome density and sesquiterpene hydrocarbon concentration similar to the wild parent was recovered among a limited number of BC2F2 individuals. Ability to set self seed was higher in families have few or no type IV trichomes and low concentrations of sesquiterpene hydrocarbons. Progeny obtained by selfing two BC2F2 individuals were field grown during the summer of 2014. More than 50 individuals in each family were evaluated for sesquiterpene concentrations and type IV trichome densities. In no case did density or concentration of any progeny exceed that of the immediate parent. In fact, recovery of the immediate parental phenotype was rare. Transgressive segregation was not observed, except for monoterpene concentrations. Additionally fruit and seed set on these BC2F3 (BC2S2) individuals was infrequent; less than 25% of the plants produced seed in the field. Concentration of sesquiterpene hydrocarbon was a quantitative character, ranging from near 0 to near 100% of the immediate parent. Distribution of individuals based on quantity of hyrdrocarbon was continuous. As stated previously BC2F2 individuals having trichome density and chemistry similar to the wild parent were rare in the BC2F2. Additionally these individuals did not set self-seed. However we used one of these individuals as a parent for backcrossing. More than 1000 BC3 seed have been generated from this cross, and approximately 60 individuals are growing in the greenhouse. Characterization of these individuals has just begun. However, we know that most individuals are self-fruitful, most individuals contain the sesquiterpene hydrocarbon in their secretions, and most have type IV trichomes. However, there appears to be segregation for type IV trichome density and for sesquiterpene and monoterpene hydrocarbon concentrations among individuals in the generation. Individuals with type IV density and sesquiterpene hydrocarbon phenotypes similar to the wild parent appear present in the population.


  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Guo, G.-J., Gao, J., Wang, X.-x., Guo, Y.-m., Snyder, J. C., & Du, Y.-c. (2014). Secondary Metabolites on Leaf Surface of Different Tomato Species. Chinese Bulletin of Botany, 49(1), 1929.
  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Antonious, G. F., Kamminga, K., & Snyder, J. C. (2014). Wild tomato leaf extracts for spider mite and cowpea aphid control. [article]. Journal of Environmental Science and Health. Part B, Pesticides, Food Contaminants, and Agricultural Wastes, 49(7), 527-531.
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Guo, G.-J., Gao, J.-C., Wang, X.-X., Guo, Y.-M., Snyder, J. C., & Du, Y.-C. (2013). QTL Analysis of Resistance to Type B Bemisia tabaci in Solanum habrochaites LA2329. Acta Horticulturae Sinica, 40(4), 663674.
  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Antonious, G. F., Turley, E. T., Hill, R. R., & Snyder, J. C. (2014). Chicken manure enhanced yield and quality of field-grown kale and collard greens. Journal of Environmental Science and Health, Part B, 49(4), 299-304.
  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Ali, S., Snyder, J., Shehzad, M., & Khalid, A. (2014). Associations among fungi, bacteria, and phytoplasma in trees suffering citrus decline in Punjab. Journal of Agricultural Technology, 10(5), 1343-1352.

Progress 01/01/13 to 09/30/13

Target Audience: Primary target audiences include tomato breeders worldwide, and researchers in host-plant resistance to insects. Final beneficiaries will be farmers who produce tomatoes. Changes/Problems: Because ofreduced resources, research aimed at understanding laminar based resistance may have to be eliminated. What opportunities for training and professional development has the project provided? I am currently recruiting an Iraqi Ph. D. student who has agreed to participate in this project. How have the results been disseminated to communities of interest? Breeders in Spain, Florida, and in China have been briefed on current results. What do you plan to do during the next reporting period to accomplish the goals? During the next reporting period arthropod resistance, type IV and VI trichome densities, type VI gland shape, and monoterpene and sesquiterpene concentrations will be assessed on a subset of the BC2F2 plants currently in the greenhouse. This information, in combination with ability to set seed after self pollination will be aggregated, and then used to decide the next steps which may include field evaluation of BC2F3 families arising from self pollination of BC2F2 individuals, additional field evaluation of certainparticularlyvaluable BC2F2families obtained from remnant seed and identification of additional desirable crosses to be made in the greenhouse.

What was accomplished under these goals? During the nine-month report period for the project, resistance to spider mites, type IV trichome density and trichome secretion composition were determined on BC2F1plants selected from the field the previous summer. Based on these evaluations and on the abilities of individual BC2F1 plants to set fruit and seeds, the self progeny of eight individuals were chosen for subsequent evaluation during the summer of 2013.Three of the individuals produced sesquiterpenoids similar tothose present in the wild parent, in their trichome secretions andthree individuals had elevated type IV trichomedensity. Oneindividual had both sesquiterpenes and high type IV density. And, one individual had no type IV trichomes and did not produce sesquiterpenes. Approximately500 BC2F2 progeny, obtained by selfing BC2F1 plants, were evaluated for type IV and VI trichome densities. Presence of type IV trichomes in the BCF2 progeny was dominant. However, parental density wasrecovered on just a few plantsand a density of type IV trichomes similar to the wild parent were recovered in the BC2F2 on a few individuals.Type IV trichomes were only present infamilies arising from parents having type IV trichomes. Likewise, only families arising from BC2F1 plants having wild parent sesquiterpenes also possessed these sesquiterpenes. Presence of sesquiterpenes was dominant, but generally at levels less than that observed on the wild parent. Concentrations similar to that on the wild parent were observed on a few BC2F2 individuals. Cuttings of select individuals, those having high type IV density, or having high sesquiterpene or monoterpene concentrations were obtained, rooted, and these plants are now under evaluation in the greenhouse for self-fruitfulness, arthropod resistance, and monoterpene and sesquiterpene composition and abundance.


  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Antonious, G.F., Silitonga, M.R., Tsegaye, T.D., Unrine, J.M., Coolong, T., Snyder, J.C., 2013. Elevated concentrations of trace elements in soil do not necessarily reflect metals available to plants. Journal of Environmental Science and Health, Part B 48, 219-225.
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Coolong, T., Law, D.M., Snyder, J.C., Rowell, B., Williams, M.A., 2013. Organic Leafy Greens Variety Trials in Kentucky: Identifying Superior Varieties for Small-scale Organic Farmers. HortTechnology 23, 241-246.
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Guo, G., Gao, J., Wang, X., Guo, Y., Snyder, J., Du, Y., 2013. Establishment of an in vitro method for evaluating whitefly resistance in tomato. Breeding science 63, 239-245.
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Colvin, S.M., Snyder, J.C., Thacker, R., Yeargan, K.V., 2013. Thinking Outside the Asclepias Box: Oleander Aphids and Honeyvine Milkweed. Annals of the Entomological Society of America 106, 214-221.

Progress 01/01/12 to 12/31/12

OUTPUTS: This project focuses on providing a better understanding of how to breed for insect resistance in tomato. Parents of the experimental populations are Zaofen 2 (Solanum lycopersicum), a cultivated tomato and LA2329, (S. habrochaites), a wild tomato that is resistant to a wide range of insects. During the past year, a large number of BC2F1 seeds was generated. The pollen parent had been selected as having high resistance to arthropods, high type IV trichome density, and abundant sesquiterpenoids in its trichome secretions. The recurrent parent was Zaofen 2, a large pink tomato. Approximately 1400 BC2F1 individuals were transplanted into the field in May 2012. Cultural conditions were those typically used for stake tomato production. The entire population was evaluated for Type IV trichome density and ability to set fruit. Frequency of high Type IV density (greater than 5/mm2) was about 10%, and frequency of ability to set fruit in the field was also about 10%. A severe, natural infestation of spidermites in the field also allowed us to evaluate resistance to this arthropod. No plant was immune to mite infestation, but at least 10% of the population displayed some resistance. Cuttings were taken of selected plants, with selection based on high Type IV trichome density and ability to set fruit. Cuttings have been grown in the greenhouse, and with regard to fruit set, ability to set fruit after self-pollination in the greenhouse agreed with fruitfulness observations in the field. Some of the selected individuals are highly resistant to spider mites, and also have high Type IV trichome densities. Thus, we have identified BC2F1 individuals that produce seed from self-pollination, and also have high Type IV trichome densities as well as arthropod resistance. Composition of trichome secretions is currently under evaluation. Approximately 25% of the plants that had been selected for fruiting in the field were parthenocarpic, producing fruit, but no seeds. However, most of the parthenocarpic fruit are small, less than 1 cm in diameter. Seeded fruit resulting from self pollination are small, 2 to 4 cm in diameter, and their color ranges from yellow to pink, depending on the particular BC2F1 individual. PARTICIPANTS: Belinda Labadie, University of Kentucky, provided technical assistance for this project. This project represents an international collaboration with colleagues in China. Active participants are Chai Min, Plant Breeder, Beijing Vegetable Research Center, Beijing Academy of Agriculture and Forestry, Beijing, and Dr. Jianchang Gao, Plant Breeder, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing, China. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Reduced use of pesticides in agriculture is a goal shared by many producers and researchers alike. One path to reduction of pesticide use is deployment of host-plant resistance, that is, breeding plants that are resistant to pests. Previous research conducted via this project, and its predecessors has successfully identified causal factors, Type IV trichome density and composition of trichome secretions, in Solanum habrochaites that confer resistance to arthropods, especially small arthropods such spider mites, and tobacco whitefly. Resistance to the latter arthropod would be especially beneficial, since these pests vector serious viral diseases of tomato, throughout many parts of the world. The most recently completed research is a breakthrough for this project in that in the past, the goal of producing hybrid plants having arthropod resistance as well as the ability to set self seed has been elusive. Achievement of this goal may lead to the ability to produce tomato plants that have resistance to arthropods, thus allowing farmers to produce tomato crops with fewer applications of insecticides.


  • T Coolong, J Snyder, R Warner, J Strang, and S Surendan, 'The Relationship between Soil Water Potential, Environmental Factors, and Plant Moisture Status for Poblano Pepper Grown Using Tensiometer-Scheduled Irrigation', International Journal of Vegetable Science, 18 (2012), 137-52.
  • J Snyder, and C Min, 'Insect Resistance in Lycopersicon Hirsutum LA2329 -- Current Status', Acta Horticulurae International Symposium on Vegetable Production, Quality, and Process Standardization in Chain: A Worldwide Perspective, 944 (2012), 15-21.
  • G.F. Antonious, S.O. Dennis, J.M. Unrine, and J.C. Snyder, 'Heavy Metals Uptake in Plant Parts of Sweetpotato Grown in Soil Fertilized with Municipal Sewage Sludge', Int J Geol, 5 (2011), 14-20.

Progress 01/01/11 to 12/31/11

OUTPUTS: A new bioassay for assessing tomato resistance to Bemesia tabaci has been developed. The assay uses leaves removed from the plant placed in flasks containing water. Genotypes are mass infested with unsexed whiteflies maintained on cucumber at a rate of 100 flies per leaf. After 8 hours leaves are removed and eggs counted. Precision and sensitivity of the bioassay was demonstrated by its ability to detect differences in oviposition among wild resistant and cultivated susceptible lines. Importantly, compared to assay of intact plants, the ex planta assay had greater precision and successfully demonstrated differences of whitefly oviposition among leaf positions. Approximately 80 BC2F1 interspecific hybrids were evaluated for whitefly resistance with the recently developed ex planta bioassay. Approximately 10 individuals were identified as having resistance to whitefly, compared to the non-resistant recurrent parent. Five QTL's have been detected associated with reduced fecundity, two located on each of chromosomes 2 and 6, with one QTL located on chromosome 5. Additionally 3 QTL's associated with non-preference were located, two on chromosome 6 and one on chromosome 2. One QTL was shared for reduced fecundity and non-preference. Approximately 400 F2 individuals resulting from selfing a BC2F1 were grown in the field during summer of 2010. This particular BC2F1 was an atypical plant, in that it was self-fruitful, and had very red, large fruit, unlike its small, pink -fruited recurrent parent. Growth of most individuals was vigorous. During August, the field was successfully infested with two-spotted spider mites. Most of the F2 individuals were highly susceptible, and were killed by the mite infestation. Approximately 30 individuals demonstrated tolerance to the mite infestation. However some of these resistant individuals had few or no fruit. Of those individuals having high fruit set, the 10 most spider mite-tolerant lines and 10 highly susceptible lines were clonally propagated and subsequently self-pollinated. Additionally, seed was collected from these 20 (10 tolerant and 10 highly susceptible) plants grown in the field. This plant material will form the basis for future research on genetics of tolerance to mite feeding in tomato. Investigation of mite resistance in a small BC2F1 population detected resistance in about 15% of the plants. The mechanism of resistance was investigated in 6 BC2F1 individuals, three susceptible and three resistant. On abaxial surfaces, the number of eggs per live mite at 72 hours was 2.1, 3.7 and 6.1 for the susceptible individuals, comparable to 4.2 eggs/live mite obtained on the susceptible recurrent parent. For the resistant BC2F1 individuals, eggs per mite ranged from 0.9 to 4.2, all values higher than those obtained for the resistant parent, 0.1 eggs/live mite. On the adaxial surface eggs/live mite ranged from 0.9 to 1.5, lower than that observed for the recurrent parent, 2.5 eggs/mite but higher than the resistant parent, 0.4 eggs/mite. PARTICIPANTS: Richard Thacker, technician at the University of Kentucky has been intimately involved with most aspects of this project. He retired during the year covered by this report. Dr. George Antonious, Kentucky State University, the 1890 Land Grant University in Kentucky, has collaborated on various aspects of the project. The work on whitefly was conducted in collaboration with Dr. Jianchang Gao, tomato breeder, Institute of Vegetables and Flowers (IVF), Chinese Academy of Agricultural Science, Beijing China. Several graduate students at IVF participated in the project, receiving training on approaches to researching insect resistance in tomato. TARGET AUDIENCES: Tomato breeders are the primary target of this research. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Whiteflies (Bemesia spp.) are important pests of tomato. These whiteflies cause direct damage to tomato, leading to several problems including loss of yield and problems with tomato ripening. Also these whiteflies serve as virus vectors. Some of these viruses cause very serious production problems. For example, tomato yellow leaf curl virus can cause a 100% crop loss if the infection occurs early in the development of the crop. Whiteflies are difficult pests to control using insecticides because it develops resistance very quickly. Development of a whitefly resistant tomato may reduce the risks and costs of tomato production in areas where whiteflies and the viruses that they transmit are present. Development of bioassays and identification of genes (QTLs - quantitative trait loci) are important steps in transferring resistance from wild to cultivated tomato, which may ultimately lead to breeding tomatoes resistant to whitefly. Spider mites are also important pests of tomato. However, their control, and especially control of associated economic damage is somewhat easier that that for whitefly. Thus, production of a mite resistant tomato would also be welcome by tomato producers, but they would likely put this goal somewhat lower on their priority needs list, certainly lower than resistance to whitefly. That said, previous work has indicated that causal mechanisms of resistance to arthropods in wild tomato often confer resistance to a range of small arthropods. Thus mechanisms of arthropod resistance can be identified with spider mites, with the reasonable expectation that associated causal factors will also confer resistance to a range of arthropods. Thus the tolerance that segregates in the interspecific BC2F2 may be a useful character conferring resistance to spider mites, and well as other arthropods. The additional work conducted with spider mites revealed differential resistance between leaf surfaces, indicating the likely involvement of trichomes in the resistance mechanism. All these observations provide potential paths leading to the production of insect resistant tomato cultivars.


  • Snyder, J., G. Antonious, and R. Thacker. (2011). A sensitive bioassay for spider mite (Tetranychus urticae) repellency: a double bond makes a difference. Experimental and Applied Acarology 55(3): 215-224.
  • Antonious GF, Dennis SO, Unrine JM, Snyder JC (2011) Ascorbic acid, B-carotene, sugars, phenols, and heavy metals in sweet potatoes grown in soil fertilized with municipal sewage sludge. Journal of Environmental Science and Health, Part B 46: 112-121