Recipient Organization
UNIVERSITY OF CALIFORNIA, DAVIS
410 MRAK HALL
DAVIS,CA 95616-8671
Performing Department
Plant Sciences
Non Technical Summary
This project supports the mission of the Agricultural Experiment Station by addressing the Hatch Act area(s) of plant and animal production, protection and health; and sustainable agriculture.Our tomato breeding and genetics research project employs wild tomato species to genetically improve cultivated tomato for agriculturally important complex traits, including tolerances to abiotic (temperature and water) stresses. We use a combination of genetics, breeding, genomics, and molecular techniques to better understand quantitative (complex) trait inheritance, map genes controlling important traits, determine genetic and genomic bases of complex traits, and transfer valuable wild-species genes to cultivated tomato. We use marker-assisted selection, which employs DNA markers tightly linked to valuable genes in wild tomato, to facilitate the transfer of wild tomato genes to cultivated tomato for breeding improvement. We create and select improved tomato germplasm (pre-bred lines) useful in breeding for improvement of tomato.
Animal Health Component
70%
Research Effort Categories
Basic
30%
Applied
70%
Developmental
(N/A)
Goals / Objectives
Progress in tomato breeding has been limited due to restricted exploitable genetic variation within cultivated tomato (Solanum lycopersicum). Wild species of tomato represents a rich, yet underutilized, source of genetic diversity for breeding. Research to understand how to best employ wild species' genetic resources for maximizing tomato improvement is essential to ensure continued breeding progress. Our central topics of investigation include: facilitating interspecific gene transfer (aka introgression); quantitative trait inheritance and expression in interspecific tomato populations and breeding lines; the genetic and genomic bases of agriculturally important quantitatively inherited traits; and effective utilization of wild tomato species' germplasm in cultivated tomato breeding.Specific project goals are to:(1) Develop interspecific tomato populations, genotype and phenotypically evaluate populations in replicated field experiments. Determine markers significantly associated with variation in trait phenotypes and map QTLs.(2) Use markers linked to QTLs to perform MAS to create lines for genetic and breeding studies. Develop and implement trait introgression strategies for breeding and development of pre-bred lines.(3) Conduct basic and applied studies on QTL expression and how QTLs act, individually and in combination, to produce trait phenotypes. Investigate effects of QTL-by-environment and QTL-by-genetic-background interactions on trait expression stability across locations and years. Investigate chromosome regions containing QTLs for important quantitative traits in more detail.
Project Methods
The overall approach used for investigating and working with agriculturally important quantitative traits is as follows. We identify wild Solanum species accessions (from TGRC, tgrc.ucdavis.edu) with agriculturally desirable traits for California tomato production, including tolerance to abiotic stresses (e.g., restricted water, high/low temperatures), tolerance to biotic stresses (diseases, pests), increased yield and fruit quality. We also employ previously created sets of introgression lines available from the TGRC in our studies. Interspecific crosses (cultivated tomato x wild species) are made and structured genetic populations created (e.g., recombinant inbred, backcross, inbred backcross, near-isogenic lines). Interspecific populations are genotyped and evaluated phenotypically for agriculturally important traits in replicated field experiments across locations and years. Statistical and linkage mapping software are used to analyze marker genotype and trait data to determine significant marker-trait associations to locate QTLs. We compare QTLs across locations, years and genetic populations for a given trait to assess QTL stability/instability and QTL by environment interactions. We determine co-localization of QTLs for individual and multiple traits, and linkage relationships among QTLs. MAS breeding is used in selection schemes to accumulate beneficial QTL alleles within breeding lines. Markers linked to genes/QTLs contributing to negative horticultural traits are used in MAS breeding for selection against undesirable genes to mitigate linkage drag effects during introgression. We pursue in-depth genetic and genomic studies on specific QTLs. Fine- and high-resolution mapping are used to more precisely localize QTLs. When feasible, these regions are examined in more detail to determine genomic structure and organization. Candidate genes/polymorphisms for QTLs may be identified using available resources such as the tomato reference genome (SGN), transcriptomics (mRNA-Seq), and sequences from wild species' genomes. Collectively, the information generated by this project will enhance efficient use of wild species resources in tomato breeding and the transfer of genes controlling desired quantitative traits to cultivated tomato for genetic improvement.