2008 Annual Report
1a.Objectives (from AD-416)
The underlying genetic bases of key attributes that influence the quality, nutritive value and marketable yield of fresh and/or processed product quality in major Solanaceous crops will be elucidated, and will facilitate the deployment in improved germplasm. Gene expression will be characterized and selectable marker strategies for improving selection efficiency will be developed. The specific goals are:.
1)Development of tomato germplasm with enhanced quality attributes including fruit firmness and carotenoid content and characterization of the genetic control of these attributes. .
2)Identification of quantitative trait loci that influence tomato anthracnose fruit rot resistance. .
3)Development of new pepper germplasm for culinary and ornamental applications; determination of the inheritance of tissue-specific anthocyanin accumulation and characterization of the control of structural and regulatory genes for anthocyanin pigmentation
1b.Approach (from AD-416)
The inheritance of tomato fruit firmness in firm and ultra-firm processing tomato germplasm developed from interspecific Lycopersicon esculentum x L. hirsutum crosses will be determined and genetic variance components estimated. The inheritance of tissue-specific carotenoid content in tomato fruit pericarp, columella and locule tissues will be characterized. Genetic stocks will be developed for use in basic studies on carotenoid accumulation and for use in development of enhanced germplasm. Using RT-PCR, the relationship between variation in lycopene content and tissue-specific expression of carotenoid biosynthetic genes will be assessed. Sequence information of genomic clones of differentially expressed genes will be used to develop selectable markers for enhanced fruit pigmentation. Recombinant L. esculentum inbred tomato lines (RILs) segregating for resistance to anthracnose fruit rot have been developed. AFLP and SSR markers that differentiate parental RIL lines will be utilized for identification of QTL linked to fruit rot resistance. Relative map positions will be determined using introgression line analysis. Pepper germplasm with unique fruit and foliage pigmentation patterns, as well as unique growth habits and fruit characteristics will be developed for culinary, ornamental and dual-purpose applications. The inheritance of growth habit, photoperiod sensitivity, and tissue-specific anthocyanin pigmentation will be studied and genotypes for respective anthocyanin regulatory genes determined via complementation. Utilizing cDNA or partial genomic clones of anthocyanin regulatory and structural genes, the expression of anthocyanin-related genes will be studied with viral-induced color break, related to viral RNA distribution, and the information utilized to develop selectable markers for these genes in pepper.
The research described in the progress report is relevant to National Program 301, Action Plan Component 2, Problem Area 2c and Component 3, Problem Areas 3b and 3c.
Tomato fruit quality. Tomato fruit color and firmness are important determinants of product quality. Exotic sources of genes for improving fruit color and firmness have not been fully exploited. We have developed a tomato breeding population consisting of a series of lines described as inbred backcross lines. This breeding population is being used to identify new genes responsible for tomato fruit firmness. Using segregating populations that have been developed to formulate a genetic model for tissue-specific carotenoid accumulation in tomato fruit, an analogous approach is being used to enhance tomato fruit color. Identification of genes responsible for firmness and color will afford new opportunities for continued progress in genetic improvement of fruit quality.
Solanaceae and anthocyanin genetics. We have been investigating anthocyanin pigmentation in Capsicum (see Accomplishments section). In order to evaluate commonality of tissue-specific regulation for anthocyanin pigmentation across diverse Solanaceous species, we initiated research to characterize anthocyanin gene expression in eggplant. A cooperator has been evaluating petunia. Preliminary results suggest striking commonalities as well as differences in the genetic control of anthocyanin pigmentation. The results will serve to better elucidate the evolution of anthocyanin color genetics and have relevance to genetic manipulation of anthocyanin pigmentation in related Solanaceous species.
Phytonutrients. An abundance of plant phytochemicals have been described with putative benefits for human health. Definitive information on the efficacy of specific compounds or classes of compounds is needed by plant breeders to develop new plants with superior health properties. Our pepper breeding and anthocyanin related research has resulted in development of novel plant types that are well-suited for addressing some of these questions. Plants are available with well characterized anthocyanin constituents whose accumulation can be induced via environmental manipulation. This makes them well-suited for efficient C-13 labeling of anthocyanin compounds and nutrition studies targeted at examining their metabolic fate. A food grade anthocyanin extraction protocol has been developed. The results will benefit the human nutrition and plant science research. The research is cooperative with the Food Components and Health Laboratory in Beltsville and the University of Maryland.
Tomato fruit firmness. Tomato fruit firmness is an important quality attribute in cultivars used for fresh (intact and fresh-cut) and processed product. New sources of firmness are needed to improve product quality. Prior research determined that fruit firmness can be measured by different methods and that different genes are responsible for firmness as measured by the respective methods. By selecting for fruit compression as well as puncture resistance, new breeding lines have been developed which combine genes for superior firmness. Cooperative trials with industry collaborators demonstrated that these breeding lines will afford new opportunities for the tomato industry to achieve continued progress in genetic improvement of fruit quality. The research is cooperative with the Produce Quality and Safety Laboratory in Beltsville, MD. This research is under National Program 301 Action Plan Component 2. Crop Informatics, Genomics, and Genetic Analyses, Problem Area 2c. Genetic Analyses and Mapping of Important Traits; and Component 3. Genetic Improvement of Crops, Problem Area 3c. Germplasm enhancement.
Pepper genetics. Within the genus Capsicum (pepper) there is an abundance of genetic diversity for plant habit, and for fruit and leaf characteristics to meet the demands for creating new plant types. Unfortunately, the inheritance pattern for many of the genes that control this diversity has not been adequately determined. Utilizing new pepper breeding lines and cultivars we have developed, we determined the inheritance of important morphological foliar, fruit and plant habit attributes. These results provide new data to clarify and extend available information on the inheritance of horticulturally desirable pepper fruit attributes and provides new information on the genetic control of leaf characters and plant habit. The information provides new knowledge on gene interaction that is essential for success in a breeding program. This research is cooperative with the ARS Floral and Nursery Products Research Unit in Beltsville. This research is under National Program 301 Action Plan Component 2. Crop Informatics, Genomics, and Genetic Analyses; Problem Area 2c. Genetic Analyses and Mapping of Important Traits.
Anthocyanin gene regulation. Color is an important characteristic of culinary horticultural commodities and ornamental plants. In breeding for color, conventional approaches rely upon visual selection. These approaches have reached their limit in creating new colors and levels of intensity in many crops. New methods are needed to ensure continued progress. Utilizing pepper plants that differ in fruit, flower, and foliar pigmentation due to their genetic makeup, we determined that lack of anthocyanin pigment accumulation was attributed to lack of expression of two regulatory genes, Myb and Myc, which control key genes in the anthocyanin biosynthetic pathway. Expression of Myb is disrupted by an insertion in the Myb coding region that is essential for proper gene function. The results are important for identification of key regulatory elements that influence anthocyanin accumulation and improved pigmentation. This research is cooperative with the ARS Floral and Nursery Products Research Unit in Beltsville and with Virginia Polytechnic Institute and State University, Blacksburg, VA. This research is under National Program 301 Action Plan Component 2. Crop Informatics, Genomics, and Genetic Analyses; Problem Area 2c. Genetic Analyses and Mapping of Important Traits.
5.Significant Activities that Support Special Target Populations
USDA sponsor for an awarded 1890 Teaching Capacity Building Grant to increase and promote biotechnology-based genetics in the undergraduate curriculum. Scientist, Department of Biology, West Virginia State University. 2007 award.
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Griesbach, R.J., Beck, R.M., Hammond, J. and Stommel, J.R. 2007. Gene Expression in the Star Mutation of Petunia xhybrida Vilm. 132:680-690.
Lightbourn, G., Griesbach, R., Stommel, J.R. 2007. Genetic basis for genotype-environment interactions influencing flavonoid gene expression in Capsicum. Molecular Genetics and Genomics. 132:824-829.
Lightbourn, G., Griesbach, R., Novotny Dura, J., Clevidence, B.A., Rao, D.D., Stommel, J.R. 2008. Effects of anthocyanin and carotenoid combinations on foliage and immature fruit color of capsicum annum l. Journal of Heredity. 99:105-111.
Stommel, J.R., Griesbach, R.J. 2008. Capsicum Annuum L. Lil' Pumpkin and Pepper Jack. HortScience. 43:935-938.
Stommel, J.R., Griesbach, R.J. 2008. Capsicum Annuum L. Midnight Creeper and Solar Eclipse. HortScience. 43:939-942.
Stommel, J.R., Griesbach, R.J. 2008. Inheritance of fruit, foliar and plant habit attributes in Capsicum L. Journal of the American Society for Horticultural Science. 133:396-407.
Labate, J.A., Grandillo, S., Fulton, T., Munos, S., Caicedo, A., Peralta, I., Ji, Y., Chetelat, R., Scott, J.W., Gonzalo, M.J., Francis, D., Yang, W., Van Der Knaap, E., Baldo, A.M., Smith-White, B., Mueller, L., Prince, J., Blanchard, N., Storey, D., Stevens, M., Robbins, M., Wang, J., Liedl, B., Oconnell, M., Stommel, J.R., Aoki, K., Iijima, Y., Slade, A., Hurst, S., Loeffler, D., Steine, M., Vafeados, D., Mcguire, C., Freeman, C., Amen, A., Goodstal, J., Facciotti, D., Van Eck, J., Causse, M. 2007. Tomato. Book Chapter. In: Kole, C. editor. Genome mapping and molecular breeding in plants. Volume 5 Vegetables. NY. Springer Publishing Co. p. 1-125.