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Development of Processing Tomato Lines Resistant to Xanthomonas gardneri: from Screening to Breeding

Liabeuf, Debora
http://rave.ohiolink.edu/etdc/view?acc_num=osu1480522067298667

Abstract Details

2016, Doctor of Philosophy, Ohio State University, Horticulture and Crop Science.
Bacterial spot of tomato is caused by four species of Xanthomonas: X. euvesicatoria, X. vesicatoria, X. perforans and X. gardneri. The disease causes lesions on tomato leaves and black spot on fruits, leading to yield loss and nonmarketable tomatoes. The bacterial species X. gardneri has been recently implicated in outbreaks of bacterial spot in processing tomato fields in Brazil, Canada and the Mid-West United States. As chemical solutions are currently not reliable to control bacterial spot, the development of varieties resistant to X. gardneri and to the other Xanthomonas species is of primary interest. This project sought to identify sources of resistance to X. gardneri, to describe the genetic basis of the trait, and to develop strategies to improve selection for bacterial spot of tomato and for agronomic and fruit quality traits To identify sources of resistance to X. gardneri, wild and cultivated tomato accessions were evaluated for Hypersensitive Response (HR) and tested under inoculated field conditions. Both evaluation methods showed phenotypic variation explained by genetics. The results of the two assays were not significantly correlated. Field evaluation mimics natural epidemics, thus this method was the most reliable to identify sources of resistance to X. gardneri. Five S. pimpinellifolium and Four S. lycopersicum var cerasiforme accessions showed low disease levels in the field. S. pimpinellifolium LA2533 and S. lycopersicum var cerasiforme LA1545 were selected as sources of resistance. To simultaneously characterize the genetics of resistance to X. gardneri and introgress the trait in processing tomato background, backcross populations were developed with LA2533 and LA1545. Families were evaluated under inoculated field conditions, and genotyped with Single Nucleotide Polymorphism (SNP) markers. Four regions where significantly associated with resistance. The allele of resistance of the Quantitative Trait Loci (QTLs) on chromosome 4 and 8 originated from the processing parent. The allele of resistance of the QTLs on chromosome 6 and 11 originated from both LA2533 and LA1545. The QTL on chromosome 11 had the strongest effect on the trait. The QTL on chromosome 11 spanned 44 Mb. In order to map the loci controlling resistance to a smaller region, Individuals carrying different recombination patterns in this region were selected and their progeny were evaluated for resistance to X. gardneri under field conditions. The region associated with resistance was reduced to 10 Mb, and its effect on resistance was confirmed. The genetic effect of the region was additive to partially dominant. Selected lines derived from LA2533 showed resistance to X. gardneri, X. euvesicatoria and X. perforans under field conditions. These lines are promising breeding material to develop elite processing tomato with high performance in humid growing region with frequent bacterial spot epidemics. Approaches considering genetic information across the whole genome might be effective to breed for resistance to bacterial spot of tomato. We evaluated performance of Genomics Selection (GS) to select lines resistant to X. euvesicatoria. GS models were trained in a breeding population developed to combine resistance to bacterial spot from several sources of resistance. Model performance was evaluated empirically in two populations derived from the training population by self-pollination (inbred progeny), or by cross-pollination (hybrid population). Bayesian Lasso (BL) and Ridge Regression (RR) led to similar results. Using prior knowledge of genetic architecture and genetic effect to develop GS models significantly improved the prediction ability of the models. In spite of small training population and low marker density, GS proved to be effective to select lines resistance to bacterial spot of tomato. GS is a promising approach to increase gain under selection for quantitative traits. But to optimize the method, it is necessary to balance selection of major phenotypic traits based on their value for growers, processers, and consumers. Our goal was to evaluate the importance of phenotypic traits for processing tomato production by estimating their effect on the success of varieties in the market, and to develop Multi Trait Indices (MTI) based on this model. We used historical data for the processing tomato production in California recorded by the Processing Tomato Advisory Board (PTAB) and by the University of California Cooperative Extension (UCCE). MTIs predicting life span and market share from phenotypic traits were developed with general linear models and tested using leave-one-out cross validation. The MTIs were significantly correlated to success metrics and selected a significantly higher proportion of successful varieties than random sampling. Yield alone performed as well as the MTIs we developed, suggesting that fruit quality has a low influence on variety success. The MTIs developed were positively influenced by yield and Brix and negatively influenced by pH and color. These MTIs could help improve gain under selection for quality traits in addition to yield.
David Francis, PhD (Advisor)
Stephen Krebs, PhD (Committee Member)
Leah McHale, PhD (Committee Member)
Sally Miller, PhD (Committee Member)
Clay Sneller, PhD (Committee Member)
314 p.
Genetics; Horticulture; Plant Sciences
tomato; Solanum lycopersicum; Solanum pimpinellifolium; Solanum lycopersicum var cerasiforme; bacterial spot of tomato; Xanthomonas gardneri; Quantitative Trait Loci; Genomic Selection; Multi-Trait Index

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Citations

  • Liabeuf, D. (2016). Development of Processing Tomato Lines Resistant to Xanthomonas gardneri: from Screening to Breeding [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1480522067298667

    APA Style (7th edition)

  • Liabeuf, Debora. Development of Processing Tomato Lines Resistant to Xanthomonas gardneri: from Screening to Breeding. 2016. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1480522067298667.

    MLA Style (8th edition)

  • Liabeuf, Debora. "Development of Processing Tomato Lines Resistant to Xanthomonas gardneri: from Screening to Breeding." Doctoral dissertation, Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1480522067298667

    Chicago Manual of Style (17th edition)

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This open access ETD is published by The Ohio State University and OhioLINK.