Progress 07/01/00 to 06/30/05
Outputs
Hundreds of accessions from different tomato wild species were screened for horticultural characteristics such as disease resistance, fruit quality, and abiotic stress tolerance. Accessions identified with desirable characteristics were hybridized with the cultivated tomato (Lycopersicon esculentum) and numerous filial and backcross populations were generated. At least four new genetic linkage maps of tomato were developed using different interspecific populations and molecular markers such as RFLPs, RGAs, ESTs, SSRs, CAPS and candidate resistance genes. Segregating populations were evaluated for various traits under field, greenhouse and growth chamber conditions. The linkage maps and phenotypic data were used for genetic characterization and identification of QTLs controlling various traits. For example, QTLs for resistance to early blight (EB; caused by fungus Alternaria solani) were identified, mapped, and examined across populations and environments. We also made
significant progress in identifying, mapping and cloning candidate disease resistance genes. To develop durable resistance, it is important to combine resistance genes from different resources. In this research, the identification and characterization of genes/QTLs for resistance in different interspecific populations will facilitate pyramiding of resistance using marker-assisted selection. However, using traditional protocols of plant breeding we have developed fresh-market and processing tomatoes with improved EB resistance. Within the past two years, we also have made considerable progress as to the identification of new sources of resistance to late blight (LB; caused by oomycete Phytophthora infestans) and identification and transferring of resistance genes/QTLs to the cultivated tomato. Significant progress also has been made in the area of tomato fruit quality. In particular, we have identified and characterize QTLs controlling different fruit quality characteristics, including
soluble solids content, lycopene contents, pH and fruit size. We have developed fresh-market and processing tomatoes with improved fruit quality, in particular with high lycopene content. Some of our germplasms have lycopene content roughly twice that of most commercial cultivars. Major progress also has been made as to discerning genetic controls of, and determining relationships among, tolerances to different abiotic stresses, including cold, salt and drought. Specifically, we identified QTLs controlling these traits in different interspecific populations and determined that while there were genes specific to each stress, some genes were common across stresses. Furthermore, investigation of the relationships among stress tolerance at different developmental stages indicated the absence of a genetic relationship between tolerance during seed germination and vegetative stage. The results suggested that to develop plants with stress tolerance during all stages of plant development,
tolerance at each stage must be considered as a separate trait. Such information is valuable for developing tomatoes with improved tolerance to different stresses.
Impacts
The wild tomato accessions identified in this study with desirable horticultural characteristics are of significant use for basic and applied research. They are used for genetic characterization, mapping and cloning of genes/QTLs controlling biologically and agriculturally important traits. They also are utilized in breeding programs for transferring desirable characteristic to tomato cultigen. Currently there is no sufficient resistance to either EB or LB in commercial cultivars of tomato. Development and use of tomato cultivars with blight resistance can save farmers millions of dollars and contribute to environmental safety. Of particular significance is our finding of new genes for resistance against aggressive isolates of P. infestans recently detected in the N. America. This finding may have global impacts on controlling LB beyond tomato crop. This research also has resulted in the development of tomatoes with extremely high levels of carotenoid lycopene. The
antioxidant capacity of lycopene is approx. twice that of beta-carotene. Some of our tomatoes may soon be released for commercial use. The development of such tomatoes is particularly important as numerous epidemiological and intervention studies have shown the relationship between dietary intake of lycopene-rich foods and decreased incidence of certain cancers and heart diseases. Our research in the area of plant stress tolerance will facilitate development of plants with tolerance to environmental stresses, which can be used for cultivation in marginal environments and contribution to global food security.
Publications
- Foolad, M. R. 2004. Recent advances in genetics of salt tolerance in tomato. Plant Cell, Tissue and Organ Culture 76: 101-119.
- Nino-Liu, D. 2004. Genetic mapping of resistance gene analogs in an interspecific population of tomato segregating for early blight resistance. Ph.D. Thesis. The Pennsylvania State University, University Park, PA, 132 pp.
- Ashrafi, M. and Foolad, M. R. 2005. Pre-sowing seed treatment: a shotgun approach to improve germination, plant growth and crop yield under saline and non-saline conditions. Advances in Agronomy, pp. 225-271.
- Foolad, M. R. 2005. Recent development in stress tolerance breeding in tomato. In: Abiotic Stresses: Plant Resistance through Breeding and Molecular Approaches. M. Ashrafi and PJC Harris, eds. The Haworth Press, Inc., New York, USA. pp. 613-684.
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Progress 01/01/04 to 12/31/04
Outputs
Screening of a large collection of tomato wild germplasm for response to fungal diseases early blight (EB) and late blight (LB) resulted in the identification of a few accessions with strong resistance to both or one of the two diseases. The newly identified disease-resistant accessions are currently being used to develop segregating populations for genetics and breeding studies. Using the previously-developed segregating populations, research has been continued to discern the genetic bases of resistance to EB and LB, tolerance to drought stress, and improved fruit quality characteristics in tomato. This includes studies of the inheritance and identification of QTLs for various traits. QTLs have been identified and compared across segregating interspecific populations, including wild species Lycopersicon hirsutum and L. pimpinellifolium as sources of resistance. To develop tomato cultivars with durable resistance, it is important that resistance QTLs be identified and
transferred to the cultivated tomato from different genetic sources. To this end, we have used various resistant resources, in particular accessions within L. pimpinellifolium, for the identification of additional resistance QTLs. Evaluations of various filial populations of crosses between such accessions and tomato-breeding lines have resulted in the identification of several new resistance QTLs. Currently, research is underway to examine the locations of QTLs in different populations. We plan to pyramid resistance QTLs in the cultivated tomato by marker-assisted transferring from both L. hirsutum and L. pimpinellifolium. Furthermore, new linkage maps of tomato have been developed using various molecular markers including RFLPs, RGAs, SSRs, ESTs, and candidate resistance genes. We have also started developing a new tomato linkage map based on a new L. esculentum x L. pimpinellifolium recombinant inbred line (RIL) population. Simultaneously, research to develop tomato germplasm with
improved desirable horticultural characteristics has been continued using traditional protocols of plant genetics and breeding. Various populations, in particular those derived from crosses between L. esculentum and red-fruited wild species L. pimpinellifolium, have been used for this purpose. The traditional breeding approach has resulted in significant progress. For example, we have developed advanced fresh-market and processing tomato genotypes with improved disease resistance, high yield, high fruit lycopene content and other desirable horticultural characteristics. Work is in progress to grow and evaluate performance of these genotypes across northeastern region of the U.S.
Impacts
EB and LB are two most destructive diseases of tomato in many tomato-growing areas in the U.S. In PA, for example, ca. 20 percent of the tomato crop is lost annually by the incidence of blight. No sufficient resistance to either disease is known in the cultivated tomato. We have identified genetic sources of resistance to EB and LB within the related wild species of tomato and have characterized the genetic controls of resistance, including the identification of QTLs. We have also developed tomato germplasm with resistance to both diseases. Some of these tomatoes will soon be released for commercial production. The development and use of resistant tomato cultivars can save farmers millions of dollars each year on fungicide application. We also have developed tomatoes with improved fruit quality, in particular tomatoes with high fruit lycopene content. The carotenoid lycopene is the red pigment and a potent natural antioxidant. Fresh tomatoes and tomato products are
the major sources of lycopene in the U.S. diet. The antioxidant capacity of lycopene is ca. twice that of beta-carotene. Dietary intake of lycopene-rich foods results in decreased incidence of certain cancers (e.g. prostate), coronary heart diseases, cataracts and macular degeneration. The development of high lycopene tomato is one step toward the production of functional food. Furthermore, genetic materials have been developed for adaptation to PA conditions specifically and to northeast U.S. generally. They are expected to outperform current commercial cultivars under U.S. northeast conditions.
Publications
- Zhang, L. P., Lin, G. Y. and Foolad, M. R. 2003. QTL comparison of salt tolerance during seed germination and vegetative growth in a Lycopersicon esculentum L. pimpinellifolium RIL population. Acta Horticulturae 618: 59-67.
- Foolad, M. R., Zhang, L. and Subbiah, P. 2003. Relationships among cold, salt and drought tolerance during seed germination in tomato: Inheritance and QTL mapping. Acta Horticulturae 618: 47-57.
- Hyman, J. R., Gaus, J. and Foolad, M. R. 2004. A rapid and accurate method for estimating tomato lycopene content by measuring chromaticity values of fruit puree. JASHS 129: 717-723.
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Progress 01/01/03 to 12/31/03
Outputs
Research to discern genetic bases of resistance to early blight (EB) and late blight (LB), tolerance to abiotic stresses, and improved fruit quality characteristics in tomato was continued. Research to develop tomato germplasm with improved desirable horticultural characteristics using traditional protocols of plant breeding was also continued. Various populations were developed from crosses between the cultivated tomato, Lycopersicon esculentum, and the related wild species L. hirsutum and L. pimpinellifolium. New molecular linkage maps of tomato have been developed using various markers including RFLPs, RGAs, SSRs, ESTs, and candidate resistance genes. The genetic basis of tomato resistance to EB, including the heritability and chromosomal locations of resistance genes (QTLs), was determined using different backcross populations from crosses between L. esculentum and L. hirsutum. The stability of resistance QTLs across populations and environments was examined.
Several stable QTLs were identified, which should be valuable for marker-assisted selection (MAS) and breeding of tomatoes with improved disease resistance. To facilitate their utility, research is underway to fine map the stable QTLs by developing a series of near-isogenic lines (NILs) and sub-NILs. This approach will not only allow validating the individual and interactive effects of the QTLs in a uniform L. esculentum background, but also facilitate minimizing linkage drag when transferring QTLs from wild to the cultivated species. However, to develop tomato cultivars with durable resistance to EB, it is important that resistance QTLs be identified and transferred to the cultivated tomato from different genetic resources. Therefore, we have used other resistant resources, in particular accessions within L. pimpinellifolium, for the identification of additional resistance QTLs. Evaluations of various filial populations of crosses between such accessions and tomato breeding lines
have resulted in the identification of several new resistance QTLs. Currently, research is underway to examine the locations of QTLs in different populations of the same interspecific crosses. We plan to pyramid resistance QTLs in the cultivated tomato by marker-assisted transferring from both L. hirsutum and L. pimpinellifolium. Simultaneous with the molecular marker approach, we also have attempted to transfer resistance genes from L. pimpinellifolium to the cultivated tomato using traditional protocols of plant breeding. This approach has resulted in measurable progress. Similar molecular and traditional genetics research also has been conducted to characterize the genetic basis of, and transfer genes for, important fruit quality characteristics in tomato. For example, we not only have identified and mapped QTLs for major fruit quality characteristics in tomato, including lycopene content, soluble solids content, fruit size and pH, but also have developed tomato germplasm with
improved fruit quality and other desirable horticultural characteristics. These genotypes will be useful for developing improved tomato lines and cultivars for commercial use.
Impacts
EB and LB are two most destructive fungal diseases of tomato in many tomato growing areas in the U.S. and elsewhere. In Pennsylvania, for example, approximately 20 percent of the tomato crop is lost annually by the incidence of blight. No sufficient resistance to either disease is known in the cultivated tomato. We have identified genetic resources for resistance to these diseases within the related wild species of tomato, and have characterized the genetic controls of resistance, including the identification of resistance QTLs. We have also developed tomato germplasm with resistance to both EB and LB. For example, we have developed some high-yielding cherry tomatoes with good resistance to both diseases and with exceptional fruit quality. Some of these tomatoes may soon be released for commercial production. The development and use of EB and LB resistant tomato cultivars can save farmers millions of dollars each year on fungicide applications. We also have developed
tomatoes with improved fruit quality, in particular tomatoes with high fruit lycopene content. The carotenoid lycopene is the red pigment and a potent natural antioxidant. Fresh tomatoes and tomato products are the major sources of lycopene in the U.S. diet. The antioxidant capacity of lycopene is approximately twice that of beta-carotene. Dietary intake of lycopene-rich foods results in decreased incidence of certain cancers (e.g. prostate), coronary heart diseases, cataracts and macular degeneration. The development of high lycopene tomato is one step toward the production of functional food.
Publications
- Foolad, M.R. 2003. Recent advances in genetics of salt tolerance in tomato. Plant Cell, Tissue and Organ Culture 76: 101-119.
- Nino-Liu, D., Zhang, L.P. and Foolad M. R. 2003. Sequence comparison and characterization of mapped resistance gene analogs markers in tomato. Acta Horticulturae 625:49-58.
- Zhang, L.P., Lin, G.L., Nino-Liu, D. and Foolad, M.R. 2003. Mapping QTLs conferring early blight (Alternaria solani) resistance in a Lycopersicon esculentum L. hirsutum cross by selective genotyping. Molec. Breeding 12:3-19.
- Foolad, M.R., Zhang, L.P. and Subbiah, P. 2003. Genetics of drought tolerance during seed germination in tomato: Inheritance and QTL mapping. Genome 46: 536-545.
- Foolad, M.R., Subbiah, P., Kramer, C., Hargrave, G., Zhang, L.P. and Lin, G.L. 2003. Genetic relationships between cold, salt and drought tolerance during seed germination in an interspecific cross of tomato. Euphytica 130:199-206.
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Progress 01/01/02 to 12/31/02
Outputs
Research to discern the genetic bases of resistance to early blight (EB) and late blight (LB) and to further understand the genetic controls of fruit quality characteristics in tomato is continued. Significant progress has also been made in breeding new tomato genotypes with improved horticultural characteristics, as briefly described below. Various new populations have been developed from crosses between the cultivated tomato, Lycopersicon esculentum, and the related wild species, including the green-fruited L. hirsutum and red-fruited L. pimpinellifolium. Two new molecular linkage maps of tomato have been developed using various markers including restriction fragment length polymorphisms (RFLPs), resistance gene analogs (RGAs), simple sequence repeats (SSRs), expressed sequence tags (ESTs) and candidate resistance genes. Using different backcross populations from crosses between L. esculentum and L. hirsutum, we have determined the genetic basis of resistance to EB,
including the heritability of resistance, chromosomal locations of resistance genes (also known as quantitative trait loci or QTLs), and cloning of resistance gene analogs. We have determined that EB resistance is genetically controlled and could be transferred from wild types to the cultivated tomato. However, EB resistance is under different genetic controls in different accessions, ranging from being a dominant trait to being a recessive trait. To develop durable resistance, therefore, it is important to combine resistance from different resources. We also have determined that accessions or genotypes that are EB resistance also often exhibit resistance to LB. Using the molecular marker technology, several QTLs for EB resistance have been identified and mapped on tomato chromosomes. The identified QTLs have also been validated in different populations, using different mapping strategies. The identified QTLs will be useful for transferring of resistance from wild species to the
cultivated tomato via marker-assisted selection (MAS). Using the various interspecific populations of tomato and the traditional protocols of plant breeding, we have transferred resistance to different fresh-market and processing tomato backgrounds and developed germplasms with improved resistance to both EB and LB. Similar research also has been conducted to characterize the genetic basis of, and transfer genes for, important fruit quality characteristics in tomato, including lycopene content, soluble solids content (SSC), fruit size and pH. For example, we have determined heritabilities of, and identified and mapped QTLs controlling, these fruit quality characteristics. Furthermore, we have transferred desirable traits to several processing and fresh-market tomato genetic backgrounds and have developed tomato genotypes with improved fruit quality and other horticultural characteristics. These genotypes will be used to develop improved tomato lines and cultivars for commercial use.
For example, we have developed some high yielding cherry tomatoes with good resistance to EB and LB and with exceptional fruit quality characteristics. Some of these tomatoes may soon be released for commercial use.
Impacts
EB and LB are two most destructive fungal diseases of tomato in many tomato growing areas in the U.S. and elsewhere. In Pennsylvania, for example, approximately 20 percent of the tomato crops are lost annually by the incidence of blight. No sufficient resistance to either disease is known in the cultivated tomato. We have identified genetic resources for resistance to these diseases within the related wild species of tomato, and have characterized the genetic controls of resistance, including the identification of resistance QTLs. We have also developed tomato germplasm with resistance to both EB and LB. For example, we have developed some high yielding cherry tomatoes with good resistance to both diseases and with exceptional fruit quality. Some of these tomatoes may soon be released for commercial production. The development and use of EB and LB resistant tomato cultivars can save farmers millions of dollars each year on fungicide applications. We also have
developed tomatoes with improved fruit quality, in particular tomatoes with high fruit lycopene content. The carotenoid lycopene is the red pigment and a potent natural antioxidant. Fresh tomatoes and tomato products are the major sources of lycopene in the U.S. diet. The antioxidant capacity of lycopene is approximately twice that of beta-carotene. Dietary intake of lycopene-rich foods results in decreased incidence of certain cancers (e.g. prostate), coronary heart diseases, cataracts and macular degeneration. The development of high lycopene tomato is an step toward the production of functional food.
Publications
- Zhang, L., Khan, A., Nino-Liu, D. and Foolad, M. R. 2002. A molecular linkage map of tomato displaying chromosomal locations of resistance gene analogs identified based on a Lycopersicon esculentum x L. hirsutum cross. Genome 45:133-146.
- Foolad, M. R., Zhang, L., Nino-Liu, D., Khan, A. and Lin, G. Y. 2002. Identification of QTLs for early blight (Alternaria solani) resistance in tomato using backcross populations of a Lycopersicon esculentum x L. hirsutum cross. Theor. Appl. Genet. 104:945-958.
- Bliss F. A., Arulsekar S., Foolad, M. R., Becerra, V., Gillen, A. M., Warburton, M. L., Dandekar, A. M., Kocsisne, G. M. and Mydin, K. K. 2002. An expanded genetic linkage map of Prunus based on an interspecific cross between almond and peach. Genome 45: 520-529.
- Foolad, M. R., Subbiah, P. and Ghangas, G. S. 2002. Parent-offspring correlation estimate of heritability for early blight resistance in tomato, Lycopersicon esculentum Mill. Euphytica 126: 291-297.
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Progress 01/01/01 to 12/31/01
Outputs
Additional useful germplasm have been identified for desirable horticultural characteristics, such as disease resistance, improved fruit quality and abiotic stress tolerance, within related wild species of tomato, in particular Lycopersicon hirsutum and L. pimpinellifolium. Some of the germplasm have been utilized to develop genetic populations for breeding purposes and basic research. We have completed the development of a new molecular linkage map of tomato based on an interspecific cross between the cultivated tomato L. esculentum and an accession of tomato wild species L. hirsutum. This map has been employed to map quantitative trait loci (QTLs) for various traits of interest, including early blight (EB) resistance and fruit quality characteristics. We have been transferring EB resistance from L. hirsutum to the cultivated tomato. Advanced germplasm with good level of EB resistance have been developed. A new molecular linkage map has also been developed based on a
cross between L. esculentum and L. pimpinellifolium. This map includes various types of molecular markers, including restriction fragment length polymorphisms (RFLPs), resistance gene analogs (RGAs) and expressed sequence tags (ESTs). The populations derived from this cross have been evaluated for disease resistance and fruit quality characteristics. Currently, we are mapping QTLs for various traits of interest in these populations. Populations derived from this cross have also been used for breeding purposes. We have developed advanced germplasm with improved fruit quality and disease resistance from this cross. For example, we have developed a cherry tomato hybrid with strong resistance to EB and late blight, intense fruit lycopene content and high fruit yield. In particular, the fruit lycopene content of this tomato hybrid is at least twice that of an average commercial cultivar of tomato. Significant progress has been made in identifying, mapping and cloning candidate disease
resistance genes in tomato. We have also conducted significant research on tomato abiotic stress tolerance. In particular, we have investigated the genetic controls of and relationships among tolerances to cold, salt and drought stress. We have identified QTLs controlling these traits in different interspecific populations and have determined that while there are genes that are specific to each stress, some genes have common effects on tolerance to all three stresses. We have also investigated the relationships among stress tolerance at different developmental stages. In particular, we have determined the absence of a genetic relationship between stress tolerance during seed germination and vegetative stage. The results suggest that to develop plants with stress tolerance during all stages of development, tolerance at each stage must be considered as a separate trait.
Impacts
This research has identified genetic resources for desirable horticultural traits in tomato. The identified germplasms are of paramount importance for both basic and applied research. For example, there is no source of genetic resistance to early blight (EB) in the cultivated tomato. In the U.S., EB can be severe in the Midwest, eastern and northeastern regions. In PA, approximately 20 percent of the tomato crop are lost each year by the incidence of this disease. The use of the identified resistant germplasm and the development of EB resistant tomatoes can save farmers millions of dollars each year on fungicide applications. We have characterized the genetic controls of EB resistance in tomato, which will facilitate the development of EB resistant tomato cultivars by using traditional protocols of plant breeding and modern techniques of molecular genetics. We have developed advanced tomato germplasm with good resistance to EB. In addition, we have developed tomatoes
with improved fruit quality, particularly with high fruit lycopene content. Numerous epidemiological and intervention studies have demonstrated that dietary intake of lycopene -rich foods results in decreased incidence of certain cancers (e.g. prostate, lung, mouth, and colon), coronary heart diseases, cataracts and macular degeneration. Our research in the area of plant stress tolerance will greatly facilitate the development of plants with tolerance to environmental stresses, including cold, salt and drought stress, which are highly needed for a sustainable production of crops in future.
Publications
- Foolad, M.R. and Lin, G. Y. 2001. Relationship between cold tolerance during seed germination and vegetative growth in tomato: Analysis of response and correlated response to selection. J. Amer. Soc. Hort. Sci. 126:216-220.
- Foolad, M.R. and Lin, G. Y. 2001. Genetic analysis of cold tolerance during vegetative growth in tomato, Lycopersicon esculentum Mill. Euphytica 122:105-111.
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Progress 01/01/00 to 12/31/00
Outputs
Hundreds of accessions from different tomato wild species, in particular the closely-related, red-fruited species 'Lycopersicon pimpinellifolium', have been evaluated for disease resistance, fruit quality, and other desirable horticultural characteristics, and useful germplasms identified. Crosses have been made between the cultivated and wild species and several populations segregating for various horticultural characteristics developed. Currently, these populations are being evaluated for several traits of interest. In addition, new molecular linkage maps are being developed based on specific crosses for mapping genes and quantitative trait loci (QTLs) and marker-assisted selection (MAS) and breeding.
Impacts
This research will identify genetic sources of desirable characteristics for tomato breeding. Genetic bases of several complex, but economically very important, traits, including early blight (EB) and late blight (LB) resistance, improved fruit quality (in particular fruit lycopene and soluble solids contents), and tolerance to environmental stresses, will be determined. This research will facilitate development of tomatoes with improved fruit quality, disease resistance and enhanced stress tolerance using contemporary techniques of molecular markers and MAS.
Publications
- No publications reported this period
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