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21 pages, 724 KiB

Open AccessArticle

Genetic Analysis of Root-to-Shoot Signaling and Rootstock-Mediated Tolerance to Water Deficit in Tomato

by Maria J. Asins, Alfonso Albacete, Cristina Martínez-Andújar, Eser Celiktopuz, İlknur Solmaz, Nebahat Sarı, Francisco Pérez-Alfocea, Ian C. Dodd, Emilio A. Carbonell and Sevilay Topcu

Genes 2021, 12(1), 10; https://doi.org/10.3390/genes12010010 - 23 Dec 2020

Cited by 12 | Viewed by 3158

Abstract

Developing drought-tolerant crops is an important strategy to mitigate climate change impacts. Modulating root system function provides opportunities to improve crop yield under biotic and abiotic stresses. With this aim, a commercial hybrid tomato variety was grafted on a genotyped population of 123 [...] Read more.

Developing drought-tolerant crops is an important strategy to mitigate climate change impacts. Modulating root system function provides opportunities to improve crop yield under biotic and abiotic stresses. With this aim, a commercial hybrid tomato variety was grafted on a genotyped population of 123 recombinant inbred lines (RILs) derived from Solanum pimpinellifolium, and compared with self- and non-grafted controls, under contrasting watering treatments (100% vs. 70% of crop evapotranspiration). Drought tolerance was genetically analyzed for vegetative and flowering traits, and root xylem sap phytohormone and nutrient composition. Under water deficit, around 25% of RILs conferred larger total shoot dry weight than controls. Reproductive and vegetative traits under water deficit were highly and positively correlated to the shoot water content. This association was genetically supported by linkage of quantitative trait loci (QTL) controlling these traits within four genomic regions. From a total of 83 significant QTLs, most were irrigation-regime specific. The gene contents of 8 out of 12 genomic regions containing 46 QTLs were found significantly enriched at certain GO terms and some candidate genes from diverse gene families were identified. Thus, grafting commercial varieties onto selected rootstocks derived from S. pimpinellifolium provides a viable strategy to enhance drought tolerance in tomato. Full article

(This article belongs to the Special Issue Tomato Genetics)

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25 pages, 1599 KiB

Open AccessArticle

GWAS Based on RNA-Seq SNPs and High-Throughput Phenotyping Combined with Climatic Data Highlights the Reservoir of Valuable Genetic Diversity in Regional Tomato Landraces

by Monica Rodriguez, Alessandro Scintu, Chiara M. Posadinu, Yimin Xu, Cuong V. Nguyen, Honghe Sun, Elena Bitocchi, Elisa Bellucci, Roberto Papa, Zhangjun Fei, James J. Giovannoni, Domenico Rau and Giovanna Attene

Genes 2020, 11(11), 1387; https://doi.org/10.3390/genes11111387 - 23 Nov 2020

Cited by 19 | Viewed by 6481

Abstract

Tomato (Solanum lycopersicum L.) is a widely used model plant species for dissecting out the genomic bases of complex traits to thus provide an optimal platform for modern “-omics” studies and genome-guided breeding. Genome-wide association studies (GWAS) have become a preferred approach [...] Read more.

Tomato (Solanum lycopersicum L.) is a widely used model plant species for dissecting out the genomic bases of complex traits to thus provide an optimal platform for modern “-omics” studies and genome-guided breeding. Genome-wide association studies (GWAS) have become a preferred approach for screening large diverse populations and many traits. Here, we present GWAS analysis of a collection of 115 landraces and 11 vintage and modern cultivars. A total of 26 conventional descriptors, 40 traits obtained by digital phenotyping, the fruit content of six carotenoids recorded at the early ripening (breaker) and red-ripe stages and 21 climate-related variables were analyzed in the context of genetic diversity monitored in the 126 accessions. The data obtained from thorough phenotyping and the SNP diversity revealed by sequencing of ripe fruit transcripts of 120 of the tomato accessions were jointly analyzed to determine which genomic regions are implicated in the expressed phenotypic variation. This study reveals that the use of fruit RNA-Seq SNP diversity is effective not only for identification of genomic regions that underlie variation in fruit traits, but also of variation related to additional plant traits and adaptive responses to climate variation. These results allowed validation of our approach because different marker-trait associations mapped on chromosomal regions where other candidate genes for the same traits were previously reported. In addition, previously uncharacterized chromosomal regions were targeted as potentially involved in the expression of variable phenotypes, thus demonstrating that our tomato collection is a precious reservoir of diversity and an excellent tool for gene discovery. Full article

(This article belongs to the Special Issue Tomato Genetics)

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22 pages, 6114 KiB

Open AccessArticle

Exploration of a Resequenced Tomato Core Collection for Phenotypic and Genotypic Variation in Plant Growth and Fruit Quality Traits

by Raana Roohanitaziani, Ruud A. de Maagd, Michiel Lammers, Jos Molthoff, Fien Meijer-Dekens, Martijn P. W. van Kaauwen, Richard Finkers, Yury Tikunov, Richard G. F. Visser and Arnaud G. Bovy

Genes 2020, 11(11), 1278; https://doi.org/10.3390/genes11111278 - 29 Oct 2020

Cited by 31 | Viewed by 7812

Abstract

A tomato core collection consisting of 122 gene bank accessions, including landraces, old cultivars, and wild relatives, was explored for variation in several plant growth, yield and fruit quality traits. The resequenced accessions were also genotyped with respect to a number of mutations [...] Read more.

A tomato core collection consisting of 122 gene bank accessions, including landraces, old cultivars, and wild relatives, was explored for variation in several plant growth, yield and fruit quality traits. The resequenced accessions were also genotyped with respect to a number of mutations or variations in key genes known to underlie these traits. The yield-related traits fruit number and fruit weight were much higher in cultivated varieties when compared to wild accessions, while, in wild tomato accessions, Brix was higher than in cultivated varieties. Known mutations in fruit size and shape genes could well explain the fruit size variation, and fruit colour variation could be well explained by known mutations in key genes of the carotenoid and flavonoid pathway. The presence and phenotype of several plant architecture affecting mutations, such as self-pruning (sp), compound inflorescence (s), jointless-2 (j-2), and potato leaf (c) were also confirmed. This study provides valuable phenotypic information on important plant growth- and quality-related traits in this collection. The allelic distribution of known genes that underlie these traits provides insight into the role and importance of these genes in tomato domestication and breeding. This resource can be used to support (precision) breeding strategies for tomato crop improvement. Full article

(This article belongs to the Special Issue Tomato Genetics)

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14 pages, 2127 KiB

Open AccessArticle

Integration of QTL, Transcriptome and Polymorphism Studies Reveals Candidate Genes for Water Stress Response in Tomato

by Isidore Diouf, Elise Albert, Renaud Duboscq, Sylvain Santoni, Frédérique Bitton, Justine Gricourt and Mathilde Causse

Genes 2020, 11(8), 900; https://doi.org/10.3390/genes11080900 - 7 Aug 2020

Cited by 18 | Viewed by 3474

Abstract

Water deficit (WD) leads to significant phenotypic changes in crops resulting from complex stress regulation mechanisms involving responses at the physiological, biochemical and molecular levels. Tomato growth and fruit quality have been shown to be significantly affected by WD stress. Understanding the molecular [...] Read more.

Water deficit (WD) leads to significant phenotypic changes in crops resulting from complex stress regulation mechanisms involving responses at the physiological, biochemical and molecular levels. Tomato growth and fruit quality have been shown to be significantly affected by WD stress. Understanding the molecular mechanism underlying response to WD is crucial to develop tomato cultivars with relatively high performance under low watering conditions. Transcriptome response to WD was investigated through the RNA sequencing of fruit and leaves in eight accessions grown under two irrigation conditions, in order to get insight into the complex genetic regulation of WD response in tomato. Significant differences in genotype WD response were first observed at the phenotypic level for fruit composition and plant development traits. At the transcriptome level, a total of 14,065 differentially expressed genes (DEGs) in response to WD were detected, among which 7393 (53%) and 11,059 (79%) were genotype- and organ-specific, respectively. Water deficit induced transcriptome variations much stronger in leaves than in fruit. A significant effect of the genetic background on expression variation was observed compared to the WD effect, along with the presence of a set of genes showing a significant genotype x watering regime interaction. Integrating the DEGs with previously identified WD response quantitative trait loci (QTLs) mapped in a multi-parental population derived from the crossing of the eight genotypes narrowed the candidate gene lists to within the confidence intervals surrounding the QTLs. The results present valuable resources for further study to decipher the genetic determinants of tomato response to WD. Full article

(This article belongs to the Special Issue Tomato Genetics)

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16 pages, 2775 KiB

Open AccessArticle

Phylogenetic Relationship of Plant MLO Genes and Transcriptional Response of MLO Genes to Ralstonia solanacearum in Tomato

by Jianlei Shi, Hongjian Wan, Wenshan Zai, Zili Xiong and Weiren Wu

Genes 2020, 11(5), 487; https://doi.org/10.3390/genes11050487 - 29 Apr 2020

Cited by 7 | Viewed by 2996

Abstract

As a broad-spectrum disease resistance factor, MLO is involved in a variety of biotic and abiotic stress responses in plants. To figure out the structural features, phylogenetic relationships, and expression patterns of MLO genes, we investigated the genome and transcriptome sequencing data of [...] Read more.

As a broad-spectrum disease resistance factor, MLO is involved in a variety of biotic and abiotic stress responses in plants. To figure out the structural features, phylogenetic relationships, and expression patterns of MLO genes, we investigated the genome and transcriptome sequencing data of 28 plant species using bioinformatics tools. A total of 197 MLO genes were identified. They possessed 5–7 transmembrane domains, but only partially contained a calmodulin-binding domain. A total of 359 polymorphic sites and 142 haplotypes were found in 143 sequences, indicating the rich nucleotide diversity of MLO genes. The MLO genes were unevenly distributed on chromosomes or scaffolds and were mainly located at the ends, forming clusters (24.1% genes), tandem duplicates (5.7%), and segment duplicates (36.2%). The MLO genes could be classified into three groups by phylogenetic analysis. The angiosperm genes were mainly in subgroup IA, Selaginella moellendorffii genes were in subgroup IA and IIIB, Physcomitrella patens genes were in subgroup IB and IIIA, and almost all algae genes were in group II. About half of the MLO genes had homologs within and across species. The Ka/Ks values were all less than 1, varying 0.01–0.78, suggesting that purifying selection had occurred in MLO gene evolution. In tomato, RNA-seq data indicated that SlMLO genes were highly expressed in roots, followed by flowers, buds, and leaves, and also regulated by different biotic stresses. qRT–PCR analysis revealed that SlMLO genes could respond to tomato bacterial wilt, with SlMLO1, SlMLO2, SlMLO4, and SlMLO6 probably involved in the susceptibility response, whereas SlMLO14 and SlMLO16 being the opposite. These results lay a foundation for the isolation and application of related genes in plant disease resistance breeding. Full article

(This article belongs to the Special Issue Tomato Genetics)

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Review

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16 pages, 1950 KiB

Open AccessReview

Breeding for Resistance to Fusarium Wilt of Tomato: A Review

by Jessica Chitwood-Brown, Gary E. Vallad, Tong Geon Lee and Samuel F. Hutton

Genes 2021, 12(11), 1673; https://doi.org/10.3390/genes12111673 - 23 Oct 2021

Cited by 45 | Viewed by 9414

Abstract

For over a century, breeders have worked to develop tomato (Solanum lycopersicum) cultivars with resistance to Fusarium wilt (Fol) caused by the soilborne fungus Fusarium oxysporum f. sp. lycopersici. Host resistance is the most effective strategy for the [...] Read more.

For over a century, breeders have worked to develop tomato (Solanum lycopersicum) cultivars with resistance to Fusarium wilt (Fol) caused by the soilborne fungus Fusarium oxysporum f. sp. lycopersici. Host resistance is the most effective strategy for the management of this disease. For each of the three Fol races, resistance has been introgressed from wild tomato species, predominately in the form of R genes. The I, I-2, I-3, and I-7 R genes have each been identified, as well as the corresponding Avr effectors in the fungus with the exception of Avr7. The mechanisms by which the R gene protein products recognize these effectors, however, has not been elucidated. Extensive genetic mapping, gene cloning, and genome sequencing efforts support the development of tightly-linked molecular markers, which greatly expedite tomato breeding and the development of elite, Fol resistant cultivars. These resources also provide important tools for pyramiding resistance genes and should support the durability of host resistance. Full article

(This article belongs to the Special Issue Tomato Genetics)

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26 pages, 2066 KiB

Open AccessReview

The Genetic Basis of Tomato Aroma

by Matteo Martina, Yury Tikunov, Ezio Portis and Arnaud G. Bovy

Genes 2021, 12(2), 226; https://doi.org/10.3390/genes12020226 - 4 Feb 2021

Cited by 46 | Viewed by 8396

Abstract

Tomato (Solanum lycopersicum L.) aroma is determined by the interaction of volatile compounds (VOCs) released by the tomato fruits with receptors in the nose, leading to a sensorial impression, such as “sweet”, “smoky”, or “fruity” aroma. Of the more than 400 VOCs [...] Read more.

Tomato (Solanum lycopersicum L.) aroma is determined by the interaction of volatile compounds (VOCs) released by the tomato fruits with receptors in the nose, leading to a sensorial impression, such as “sweet”, “smoky”, or “fruity” aroma. Of the more than 400 VOCs released by tomato fruits, 21 have been reported as main contributors to the perceived tomato aroma. These VOCs can be grouped in five clusters, according to their biosynthetic origins. In the last decades, a vast array of scientific studies has investigated the genetic component of tomato aroma in modern tomato cultivars and their relatives. In this paper we aim to collect, compare, integrate and summarize the available literature on flavour-related QTLs in tomato. Three hundred and fifty nine (359) QTLs associated with tomato fruit VOCs were physically mapped on the genome and investigated for the presence of potential candidate genes. This review makes it possible to (i) pinpoint potential donors described in literature for specific traits, (ii) highlight important QTL regions by combining information from different populations, and (iii) pinpoint potential candidate genes. This overview aims to be a valuable resource for researchers aiming to elucidate the genetics underlying tomato flavour and for breeders who aim to improve tomato aroma. Full article

(This article belongs to the Special Issue Tomato Genetics)

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12 pages, 1905 KiB

Open AccessReview

The Tomato Interspecific NB-LRR Gene Arsenal and Its Impact on Breeding Strategies

by Giuseppe Andolfo, Nunzio D’Agostino, Luigi Frusciante and Maria Raffaella Ercolano

Genes 2021, 12(2), 184; https://doi.org/10.3390/genes12020184 - 27 Jan 2021

Cited by 8 | Viewed by 4281

Abstract

Tomato (Solanum lycopersicum L.) is a model system for studying the molecular basis of resistance in plants. The investigation of evolutionary dynamics of tomato resistance (R)-loci provides unique opportunities for identifying factors that promote or constrain genome evolution. Nucleotide-binding domain and leucine-rich [...] Read more.

Tomato (Solanum lycopersicum L.) is a model system for studying the molecular basis of resistance in plants. The investigation of evolutionary dynamics of tomato resistance (R)-loci provides unique opportunities for identifying factors that promote or constrain genome evolution. Nucleotide-binding domain and leucine-rich repeat (NB-LRR) receptors belong to one of the most plastic and diversified families. The vast amount of genomic data available for Solanaceae and wild tomato relatives provides unprecedented insights into the patterns and mechanisms of evolution of NB-LRR genes. Comparative analysis remarked a reshuffling of R-islands on chromosomes and a high degree of adaptive diversification in key R-loci induced by species-specific pathogen pressure. Unveiling NB-LRR natural variation in tomato and in other Solanaceae species offers the opportunity to effectively exploit genetic diversity in genomic-driven breeding programs with the aim of identifying and introducing new resistances in tomato cultivars. Within this motivating context, we reviewed the repertoire of NB-LRR genes available for tomato improvement with a special focus on signatures of adaptive processes. This issue is still relevant and not thoroughly investigated. We believe that the discovery of mechanisms involved in the generation of a gene with new resistance functions will bring great benefits to future breeding strategies. Full article

(This article belongs to the Special Issue Tomato Genetics)

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