Development of Processing Tomato Lines Resistant to <i>Xanthomonas gardneri</i>: from Screening to Breeding
Bibliographic record
Abstract
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 iii 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 xvi
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.003 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".