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The tomato collection maintained by AVRDC – The World Vegetable Center: composition, germplasm dissemination and use in breeding

Authors:
Andreas Ebert at World Vegetable Center
Andreas Ebert
Yu-Yu Chou at World Vegetable Center
Yu-Yu Chou
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Abstract

With about 84,300 accessions, the section Lycopersicon in the genus Solanum is well-represented in ex situ collections around the globe. The single largest collection (approximately 9.7% of total global resources) is held by AVRDC – The World Vegetable Center in Taiwan, followed by genebanks in the US, the Philippines, Germany, the Russian Federation, and Japan. AVRDC's tomato collection is composed of cultivated tomato (6041 S. lycopersicum accessions—mostly traditional cultivars and landraces, and 125 S. lycopersicum var. cerasiforme accessions), crop wild relatives (805 accessions), and genetic stocks (595 accessions) composed of interspecific hybrids, introgressed lines, and recombinant inbred lines. A total of 585 accessions still lack proper species identification. After pepper (Capsicum spp.), tomato is AVRDC's second most widely distributed vegetable crop. Wild relatives of tomato have been crucial in the improvement of pest and disease resistance and abiotic stress tolerance of cultivated tomato through classical breeding. Virtually all significant resistance genes to tomato diseases were sourced from wild relatives. Research work at AVRDC has focused on the introduction of resistance genes into cultivated tomato against late blight, bacterial wilt and leaf curl (caused by begomoviruses) and the development of heat-tolerant lines. Since 1978, 186 tomato cultivars have been released in 44 countries worldwide based on AVRDC-developed open-pollinated, heat-tolerant and multiple disease-resistant germplasm. This success was possible due to the genetic building blocks conserved in AVRDC's diverse tomato collection.
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THE TOMATO COLLECTION MAINTAINED BY AVRDC – THE WORLD
VEGETABLE CENTER: COMPOSITION, GERMPLASM DISSEMINATION AND
USE IN BREEDING
Ebert, AW1, Chou, Y-Y1
andreas.ebert@worldveg.org
1 AVRDC – The World Vegetable Center, Shanhua, Tainan, Taiwan
With about 84,300 accessions, the section Lycopersicon in the genus Solanum is
well-represented in ex situ collections around the globe. The single largest collection
(approximately 9.7% of total global resources) is held by AVRDC – The World
Vegetable Center in Taiwan, followed by genebanks in the US, the Philippines,
Germany, the Russian Federation, and Japan. AVRDC’s tomato collection is
composed of cultivated tomato (6041 S. lycopersicum accessions—mostly traditional
cultivars and landraces, and 125 S. lycopersicum var. cerasiforme accessions), crop
wild relatives (805 accessions), and genetic stocks (595 accessions) composed of
interspecific hybrids, introgressed lines, and recombinant inbred lines. A total of 585
accessions still lack proper species identification. After pepper (Capsicum spp.),
tomato is AVRDC’s second most widely distributed vegetable crop. Wild relatives of
tomato have been crucial in the improvement of pest and disease resistance and
abiotic stress tolerance of cultivated tomato through classical breeding. Virtually all
significant resistance genes to tomato diseases were sourced from wild relatives.
Research work at AVRDC has focused on the introduction of resistance genes into
cultivated tomato against late blight, bacterial wilt and leaf curl (caused by
begomoviruses) and the development of heat-tolerant lines. Since 1978, 186 tomato
cultivars have been released in 44 countries worldwide based on AVRDC-developed
open-pollinated, heat-tolerant and multiple disease-resistant germplasm. This
success was possible due to the genetic building blocks conserved in AVRDC’s
diverse tomato collection.

Supplementary resource (1)

The tomato collection maintained by AVRDC – The World Vegetable Center - composition, germplasm dissemination and use in breeding
Data
November 2015
Andreas Ebert · Yu-Yu Chou
... Public genebanks, such as the World Vegetable Center (WorldVeg), maintain extensive collections of tomato landraces and crop wild relatives (Bauchet & Causse 2012;Ebert & Chou 2014). Despite considerable progress in characterizing these genetic resources, two critical challenges persist. ...
Molecular screening of wild and cultivated tomato germplasm reveals potential materials for multi-locus disease resistance breeding
Article
Full-text available
  • May 2025
  • GENET RESOUR CROP EV
Tomato (Solanum lycopersicum L.) production faces major yield loss due to biotic stresses. Developing genetically resistant cultivars presents a sustainable alternative to chemical controls, which are often costly and ineffective. This study utilized 10 molecular markers, including SSR, SCAR, and CAPS markers, to assess resistance to six major diseases, including Fusarium wilt, late blight, bacterial wilt, root-knot nematode, Tomato Mosaic Virus (ToMV), and Tomato Yellow Leaf Curl Virus (TYLCV), across 964 tomato accessions comprising both wild germplasm (371) and cultivars (593). Wild germplasm, especially S. peruvianum, showed the highest frequencies of resistance loci. Markers linked to TYLCV and Fusarium wilt were particularly prevalent, with frequencies of 31.8% (TY-1/3_K), 34.0% (P1-16), and 55.8% (I2(OH)). Several wild accessions carried up to six resistance loci, highlighting the potential for gene pyramiding and the utility of wild species as reservoirs of multi-locus resistance. In contrast, resistance loci were limited in S. lycopersicum. Two S. lycopersicum germplasm collections were screened: a geographically representative collection from four Southeast Asian national genebanks and a genetically representative core collection from global public genebanks. The highest resistance frequencies in S. lycopersicum were observed for bacterial wilt-associated markers SLM12-2 and SLM12-10. However, the overall scarcity of resistance alleles in S. lycopersicum emphasizes the need for further introgression of resistance genes from wild relatives. This study provides valuable genetic insights into tomato germplasm for combating biotic stress, forming a foundation for sustainable breeding strategies to enhance disease resistance and safeguard global tomato production.
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... One important strategy involves using plant genetic resources to identify and develop pest and disease-resistant cultivars that can maintain high levels of production with less dependence on inputs (Atlin et al. 2017). The World Vegetable Center in Taiwan has a global germplasm collection of 6041 tomato accessions, with major research activities including breeding for resistance to late blight, bacterial wilt, TYLCD, and heat tolerance (Ebert and Chou 2015). Additionally, the use of improved production systems, such as low-cost structures, can also be deployed by farmers to mitigate the effects of climate change. ...
Adaptability and Yield Performance of Introduced Tomato Lines under Greenhouse and Open Field Conditions in Honduras
Article
Full-text available
  • Jul 2024
  • HORTSCIENCE
In Honduras, tomato ( Solanum lycopersicum L.) is an economically important crop for farmers because of its high domestic consumption, year-round production, and high export potential. However, tomato production faces challenges such as diseases and pests and is confounded by climate change, all of which reduce productivity and quality. Evaluating the adaptation of tomato cultivars is critical to ensuring the long-term sustainability and resilience of the horticulture sector in the region. The objective of this study was to identify tomato lines with adaptability, high yield, pest, and disease resistance under greenhouse and open field production conditions for the Honduran market. Ten tomato lines and two commercial hybrids were evaluated between Feb and Jul 2022 in San Antonio de Oriente, Francisco Morazán, Honduras. Desirable traits related to vegetative growth, productivity, fruit quality, and resistance to insect pests and diseases were measured. Seven lines were highly adapted and had high vegetative growth. The tomato lines were not significantly different in terms of tomato yellow leaf curl disease and late blight disease index; however, the fruit borer susceptibility varied, with AVTO1908 being the most susceptible. The highest performing line was AVTO1903, which had the greatest total marketable yield in both the open field (101.3 t⋅ha ⁻¹ ) and greenhouse (62.1 t⋅ha ⁻¹ ). Additionally, AVTO1903 and AVTO1915 had good quality traits (roundness index, total soluble solids, and dry matter), thus demonstrating their potential for sustainable and high-yielding cultivation in Honduras. The growth and productivity of the tomato lines were highly influenced by the environment. This work highlights the advantages of introducing exotic cultivars to combat the effects of climate change and ensure sustained production; however, further research is needed to ensure that local farmer and consumer demands are met.
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... S. pimpinellifolium played a vital role in the development of heattolerant tomato varieties in Taiwan [17]. In Nigeria, it showed better responses to high humidity compared to the cultivated elite tomatoes [18]. ...
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... Different types of techniques are used to detect molecular markers and allow the analysis of variation in the DNA molecule; restriction, and different types of Polymerase Chain Reaction (PCR) are some of them, with multiplex PCR being one of the most frequently used to identify molecular markers by using primer sets within a single PCR mix to produce amplicons of different sizes. This variant of PCR targets multiple markers or genes at once in a single test that would otherwise require several times the reagents and more time to run [11,12]. ...
Response Surface Methodology for Optimization of Multiplex-PCR Protocols for Detection of TYLCV, TSWV and Fol Molecular Markers: Analytical Performance Evaluation
Article
Full-text available
  • Jan 2023
Molecular markers linked to disease resistance genes which affect economically important crops are of great interest. In the case of tomato, a major focus on resistance breeding to multiple fungal and viral pathogens such as Tomato yellow leaf curl virus (TYLCV), Tomato spotted wilt virus (TSWV) and Fusarium oxysporum f. sp. lycopersici (Fol), have led to the introgression of several resistance genes; therefore, molecular markers have become important in molecular-assisted selection (MAS) of tomato varieties resistant to those pathogens. However, assays that allow simultaneous evaluation of resistant genotypes, such as multiplex PCR, need to be optimized and evaluated to demonstrate their analytical performance, as many factors can affect them. This work aimed to generate multiplex PCR protocols for the joint detection of the molecular markers associated with pathogen resistance genes in tomato plants that are sensitive, specific and repeatable. For the optimization a central composite design of a response surface methodology (RSM-CCD) was used. For analytical performance evaluation, specificity/selectivity and sensibility (limit of detection and dynamic range) were analyzed. Two protocols were optimized: the first one with a desirability of 1.00, contained two markers (At-2 and P7-43) linked to I- and I-3-resistant genes. The second one with a desirability of 0.99, contained markers (SSR-67, SW5 and P6-25) linked to I-, Sw-5-, and Ty-3-resistant genes. For protocol 1, all the commercial hybrids (7/7) were resistant to Fol, and for protocol 2, two hybrids were resistant to Fol, one to TSWV and one to TYLCV with good analytical performance. In both protocols, the varieties considered susceptible to the pathogens, no-amplicon or susceptible amplicons, were observed. The optimized multiplex PCR protocols showed dynamic ranges from 5.97 up to 161.3 ng DNA. The limit of detection was 17.92 ng and 53.76 ng DNA for protocols 1 and 2, respectively, giving 100% positive results in the test replicates. This method allowed to develop optimized multiplex PCR protocols with few assays which translates into less time and resources, without sacrificing method performance.
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... Preserving these germplasm collections is crucial for facing challenges of food and agricultural systems in the coming decades, related to demographic trends, climate changes, and the needing for more sustainable use of resources [21]. It is estimated that more than 80 thousand accessions are kept ex-situ across genebanks located around the globe [22]. The largest collection is held at the World Vegetable Center (WorldVeg, Tainan, Taiwan) [23], comprising over 8,200 cultivated tomato, mostly cultivars and lan-draces and several hundred accessions of wild species. ...
Next generation sequencing technologies to explore the diversity of germplasm resources: Achievements and trends in tomato
Article
Full-text available
  • Nov 2022
Tomato is one of the major vegetable crops grown worldwide and a model species for genetic and biological research. Progress in genomic technologies made possible the development of forefront methods for high-scale sequencing, providing comprehensive insight into the genetic architecture of germplasm resources. This review revisits next-generation sequencing strategies and applications to investigate the diversity of tomato, describing the common platforms used for SNP genotyping of large collections, de novo sequencing, and whole genome resequencing. Significant findings in evolutionary history are outlined, thus discussing how genomics has provided new hints about the processes behind domestication. Finally, achievement and perspectives on pan-genome construction and graphical pan-genome development toward precise mining of the natural variation to be exploited for breeding purposes are presented.
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Implication of quality uncertainty on market exchange: the case of seed industry in Kilolo district, Tanzania
Article
Full-text available
  • May 2021
An increasing demand of agricultural intensification and value addition necessitates the use of improved inputs such as improved seed. Smallholder farmers contribute about 70% of agricultural production in Tanzania. Agriculture sector in Tanzania contributes about 24.1% of the GDP, 30% of exports and 65% of industrial raw materials. Thus, agriculture development, economic growth and industrialization are inseparable. Due to the nature of the product, smallholder farmers cannot judge the overall excellence of seed at the time of buying. This paper assessed quality uncertainty in maize and vegetable seed and its implication for market exchange between farmers and seed sellers in Kilolo district, Iringa Tanzania. The study used a random sample of 130 smallholder farmers and representatives from ten seed companies. Asymmetric information prevails between the two trading sides, i.e. sellers and buyers, leading into quality uncertainty. Moreover, product augmentation is profoundly overlooked whereby most of seed companies have not augmented their products. Because an improved seed is a quintessential example of an experience good, quality uncertainty of some crop varieties under field conditions favored some seed brands to be used more by farmers compared to others. This paper offers a thorough deduction on quality uncertainty under farmers' field condition and its implication on market exchange. It adds information in the body of knowledge on how an improved seed can contribute to sustainable production of food and industrial raw materials, which is a step towards desired industrialization agenda in Tanzania.
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Collaboration between Private and Public Genebanks in Conserving and Using Plant Genetic Resources
Article
Full-text available
  • Jan 2024
Among the most important users of plant genetic resources, conserved predominantly in public genebanks around the world, are public and private plant breeders. Through their breeding efforts, they contribute significantly to global, regional, and local food and nutrition security. Plant breeders need genetic diversity to be able to develop competitive new varieties that are adapted to the changing environmental conditions and suit the needs of consumers. To ensure continued and timely access to the genetic resources that contain the required characteristics and traits, plant breeders established working collections with breeding materials and germplasm for the crops they were breeding. However, with the changing and increasingly more restrictive access conditions, triggered by new global legal instruments like the Convention on Biological Diversity/Nagoya Protocol and the International Treaty, plant breeders started to establish their own genebanks at the turn of the 21st century. This paper analyses the conditions that contributed to this situation as well as the historical ways that plant breeders used to acquire the germplasm they needed. Public genebanks played and continue to play a conducive role in providing genetic resources to users, including private-sector plant breeders. However, also the practices of the germplasm curators to collect and distribute germplasm were affected by the new legal framework that had been developed in global fora. It is against this background that the complementarity and collaboration between public and private sector genebanks have been assessed. Whenever possible, vegetable genetic resources and vegetable private breeding companies have been used to analyze and illustrate such collaboration. The authors look at reported successful examples of collaborative efforts and consider opportunities and approaches under which such collaboration can be established and strengthened to ensure the continued availability of the building blocks for food and nutrition security.
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Hybrids and abiotic stress tolerance in horticultural crops
Chapter
Full-text available
  • Jan 2021
Horticultural crops need more attention in cultivation due to their organoleptic and nutritional properties. Abiotic stresses such as drought, flood, heat, cold, salinity, nutrient deficiency, and heavy metal stress strongly impair the growth and productivity of horticultural crops. Further, climate change has also increased the risk of abiotic stresses and affects the growth and quality of the crops. It is imperative to understand the mechanism underlying abiotic stress tolerance in different crop species as tolerant plants may switch on or off different physiological or biochemical pathways to acclimatize or to overcome the unfavorable effect of abiotic stresses. Potential for tolerance and susceptibility to a specific abiotic stress vary in different crop species. Even some wild relatives and exotic germplasms are carriers of abiotic stress–tolerant genes or QTLs that can be employed to develop resistant hybrids by incorporating such genes into susceptible cultivars. The development of smart climate-resilient hybrids is one of the best alternatives to lessen the losses due to abiotic stresses. Classical breeding alone does not suffice to meet the needs of abiotic stress–tolerant hybrids. There is a need to utilize the untapped potential of modern plant breeding strategies, say double haploid technology, transgenic methods, somaclonal variation, somatic hybridization, marker-assisted backcrossing breeding, genome-wide association studies, and genomic selection to develop hybrids with improved performance and resistance against abiotic stress. In this chapter, we have tried to emphasize the importance of hybrids to tolerate abiotic stresses and the mechanism of abiotic stress tolerance in horticultural crops.
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Implication of quality uncertainty on market exchange: The case of seed industry in Kilolo district, Tanzania.
Article
Full-text available
  • May 2021
An increasing demand of agricultural intensification and value addition necessitates the use of improved inputs such as improved seed. Smallholder farmers contribute about 70% of agricultural production in Tanzania. Agriculture sector in Tanzania contributes about 24.1% of the GDP, 30% of exports and 65% of industrial raw materials. Thus, agriculture development, economic growth and industrialization are inseparable. Due to the nature of the product, smallholder farmers cannot judge the overall excellence of seed at the time of buying. This paper assessed quality uncertainty in maize and vegetable seed and its implication for market exchange between farmers and seed sellers in Kilolo district, Iringa Tanzania. The study used a random sample of 130 smallholder farmers and representatives from ten seed companies. Asymmetric information prevails between the two trading sides i.e. sellers and buyers leading into quality uncertainty. Moreover, product augmentation is profoundly overlooked whereby most of seed companies have not augmented their products. Because an improved seed is a quintessential example of an experience good, quality uncertainty of some crop varieties under field conditions favored some seed brands to be used more by farmers compared to others. This paper offers a thorough deduction on quality uncertainty under farmers’ field condition and its implication on market exchange. It adds information in the body of knowledge on how an improved seed can contribute to sustainable production of food and industrial raw materials, which is a step towards desired industrialization agenda in Tanzania.
View
Implication of quality uncertainty on market exchange: The case of seed industry in Kilolo district, Tanzania.
Article
Full-text available
  • Sep 2020
An increasing demand of agricultural intensification and value addition necessitates the use of improved inputs such as improved seed. Smallholder farmers contribute about 70 % of agricultural production in Tanzania. Agriculture sector in Tanzania contributes about 24.1 % of the GDP, 30 % of exports and 65% of industrial raw materials. Thus, agriculture development, economic growth and industrialization are inseparable. Due to the nature of the product, smallholder farmers cannot judge the overall excellence of seed at the time of buying. This paper assessed quality uncertainty in maize and vegetable seed and its implication for market exchange between farmers and seed sellers in Kilolo district, Iringa Tanzania. The study used a random sample of 130 smallholder farmers and representatives from ten seed companies. Asymmetric information prevails between the two trading sides i.e. sellers and buyers leading into quality uncertainty. Moreover, product augmentation is profoundly overlooked whereby most of seed companies have not augmented their products. Because an improved seed is a quintessential example of an experience good, quality uncertainty of some crop varieties under field conditions favored some seed brands to be used more by farmers compared to others. This paper offers a thorough deduction on quality uncertainty under farmers’ field condition and its implication on market exchange. It adds information in the body of knowledge on how an improved seed can contribute to sustainable production of food and industrial raw materials, which is a step towards desired industrialization agenda in Tanzania.
View
Identification of major QTLs associated with stable resistance of tomato cultivar ‘Hawaii 7996’ to Ralstonia solanacearum
Article
Full-text available
  • Nov 2012
  • EUPHYTICA
Bacterial wilt caused by Ralstonia solanacearum is one of the most devastating diseases of tomato. Tomato cultivar ‘Hawaii 7996’ has been shown to have stable resistance against different strains under different environments. This study aimed to locate quantitative trail loci (QTLs) associated with stable resistance using 188 recombinant inbred lines (RILs) derived from ‘Hawaii 7996’ and ‘West Virginia 700.’ A new linkage map with good genome coverage was developed, mainly using simple sequence repeat markers developed from anchored bacterial artificial chromosome or scaffold sequences of tomato. The population was evaluated against phylotype I and phylotype II strains at seedling stage or in the field in Indonesia, Philippines, Taiwan, Thailand, and Reunion. Two major QTLs were identified to be associated with stable resistance. Bwr-12, located in a 2.8-cM interval of chromosome 12, controlled 17.9–56.1 % of total resistance variation. The main function of Bwr-12 was related to suppression of internal multiplication of the pathogen in the stem. This QTL was not associated with resistance against race 3-phylotype II strain. Bwr-6 on chromosome 6 explained 11.5–22.2 % of the phenotypic variation. Its location differed with phenotype datasets and was distributed along a 15.5-cM region. The RILs with the resistance allele from both Bwr-12 and Bwr-6 had the lowest disease incidence, which was significantly lower than the groups with only Bwr-12 or Bwr-6. Our studies confirmed the polygenic nature of resistance to bacterial wilt in tomato, and that stable resistance in ‘Hawaii 7996’ is mainly associated with Bwr-6 and Bwr-12.
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Pyramiding of genes conferring resistance to Tomato yellow leaf curl virus from different wild tomato species
Article
Full-text available
  • Dec 2008
  • PLANT BREEDING
Tomato (Solanum lycopersicum) production in tropical and subtropical regions of the world is limited by the endemic presence of Tomato yellow leaf curl virus (TYLCV). Breeding programmes aimed at producing TYLCV-resistant tomato cultivars have utilized resistance sources derived from wild tomato species. So far, all reported breeding programmes have introgressed TYLCV resistance from a single wild tomato source. Here, we tested the hypothesis that pyramiding resistances from different wild tomato species might improve the degree of resistance of the domesticated tomato to TYLCV. We have crossed TYLCV-resistant lines that originated from different wild tomato progenitors, Solanum chilense, Solanum peruvianum, Solanum pimpinellifolium, and Solanum habrochaites. The various parental resistant lines and the F1 hybrids were inoculated in the greenhouse using viruliferous whiteflies. Control, non-inoculated plants of the same lines and hybrids were exposed to non-viruliferous whiteflies. Following inoculation, the plants were scored for disease symptom severity, and transplanted to the field. Resistance was assayed by comparing yield of inoculated plants to those of the control non-inoculated plants of the same variety. Results showed that the F1 hybrids between the resistant lines and the susceptible line suffered major yield reduction because of infection, but all hybrids were more resistant than the susceptible parent. All F1 hybrids resulting from a cross between two resistant parents, showed a relatively high level of resistance, which in most cases was similar to that displayed by the more resistant parent. In some cases, the hybrids displayed better levels of resistance than both parents, but the differences were not statistically significant. The F1 hybrid between a line with resistance from S. habrochaites and a line with resistance from S. peruvianum (HAB and 72-PER), exhibited the lowest yield loss and the mildest level of symptoms. Although the resistance level of this F1 hybrid was not statistically different from the level of resistance displayed by the 72-PER parent itself, it was statistically better than the level of resistance displayed by the F1 hybrids between 72-PER and any other resistant or susceptible line.
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Molecular dissection of Tomato leaf curl virus resistance in tomato line TY172 derived from Solanum peruvianum
Article
Full-text available
  • Jun 2009
  • THEOR APPL GENET
Tomato yellow leaf curl virus (TYLCV) is devastating to tomato (Solanum lycopersicum) crops and resistant cultivars are highly effective in controlling the disease. The breeding line TY172, originating from Solanum peruvianum, is highly resistant to TYLCV. To map quantitative trait loci (QTLs) controlling TYLCV resistance in TY172, appropriate segregating populations were analyzed using 69 polymorphic DNA markers spanning the entire tomato genome. Results show that TYLCV resistance in TY172 is controlled by a previously unknown major QTL, originating from the resistant line, and four additional minor QTLs. The major QTL, we term Ty-5, maps to chromosome 4 and accounts for 39.7-46.6% of the variation in symptom severity among segregating plants (LOD score 33-35). The minor QTLs, originated either from the resistant or susceptible parents, were mapped to chromosomes 1, 7, 9 and 11, and contributed 12% to the variation in symptom severity in addition to Ty-5.
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RFLP analysis of phylogenetic relationships and genetic variation in the genus Lycopersicon
Article
  • Oct 1990
Forty single-copy, nuclear probes of known chromosomal position were used to examine restriction fragment length polymorphism in the tomato genus Lycopersion. The probes were from three libraries: one cDNA, and two genomic libraries [Symbol: see text]ne genomic made with EcoRI and the other with PstI. Total DNA from 156 plants representing eight species was cut with five different restriction enzymes and scored in 198 probe-enzyme combinations. Genetic distances between accessions (populations) and species were calculated from the resultant restriction patterns and proportion of shared bands. Accessions belonging to the same species largely clustered together, confirming their current classification. However, one mountain accession, classified as L. peruvianum var. humifusum (LA2150), was sufficiently distinct from the other accessions of L. peruvianum that it may qualify as a separate species L. esculentum and L. pimpinellifolium were the least clearly differentiated, possibly reflecting introgressive hybridization, known to have been promoted by man in recent history. Dendrograms constructed from cDNA versus genomic clones were nearly identical in their general grouping of species. The dendrograms revealed two major dichotomies in the genus: one corresponding to mating behavior [self-compatible (SC) versus self-incompatible (SI) species] and the other corresponding to fruit color (red versus green-fruited species). The ratio of withinversus between-accession diversity was much lower for SC species, indicating that most of the diversity within these species exists between populations, rather than within populations. Overall, the amount of genetic variation in the SI species far exceeded that found in SC species. This result is exemplified by the fact that more genetic variation could be found within a single accession of one of the SI species (e.g., L. peruvianum) than among all accessions tested of any one of the SC species (e.g., L. esculentum or L. pimpinellifolium). Results from this study are discussed in relationship to germ plasm collection/utilization and with regard to the use of RFLPs in tomato breeding and genetics.
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Comparing heat stress effects on male‐fertile and male‐sterile tomatoes
Article
To separate the effects of heat stress on male and female reproductive tissues, male-sterile (MSs) and male-fertile tomatoes (MFs) were placed in growth chambers at 12 h day/12 h night temperatures of 28/22, 30/24 or 32/26 °C from flower appearance to seed maturation (daily mean temperatures of 25, 27 or 29 °C). Pollen from MFs was applied individually to MS flowers. As MFs were self-pollinated, heat stress was experienced by both male and female tissues. At growth temperatures of 29 °C fruit number, fruit weight per plant, and seed number per fruit were only 10%, 6·4% and 16·4%, respectively, compared with those at 25 °C. Heat stress also adversely affected fruitset in MSs, especially when experienced by donor pollen. No fruit at all developed on MSs receiving pollen produced at 29 °C, even when ovule development, pollen germination and subsequent embryo development all took place at 25 °C. Effects on fruitset in MSs were reduced if donor pollen had not experienced heat stress. MSs grown at 29 °C but receiving pollen developing at 25 °C produced 73% as much fruit (both on number and weight basis), had 40% as high fruitset and produced 87% of the seed per fruit as MSs grown at 25 °C. This use of male-sterile and male-fertile lines of tomato provides new evidence that impairment of pollen and anther development by elevated temperature will be an important contributing factor to decreased fruit set in tomato, and possibly other crops, with global warming.
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Sources of Resistance, Inheritance, and Location of Genetic Loci Conferring Resistance to Members of the Tomato-Infecting Begomoviruses
Chapter
  • Jan 2007
Several management strategies have been implemented in different regions of the world for control of the tomato-infecting begomoviruses. These have included planting virus-free tomato seedlings, applying insecticides, using insect-proof netting, and implementing a whitefly-host-free period. Recently, tomato cultivars with various levels of resistance have become available for some parts of the world. The use of resistant hybrids offers many advantages; and when used with integrated pest-management methods, these resistant hybrids can ensure that the growers will have a tomato crop. Plant breeders face tremendous challenges, because of the diversity of tomato-infecting begomoviruses. A further concern for plant breeders is the introduction of exotic tomato-infecting begomovirus into a country. This occurred in the Caribbean islands with the introduction of TYLCV from the eastern Mediterranean and resulted in serious crop losses (Salati et al., 2002). Plant breeding programs can employ molecular analysis to track resistance genes in a marker-assisted selection (MAS) breeding scheme. These tools will be important in breeding the next generation of begomovirus-resistant hybrids, which are likely to have multiple-resistance genes from different wild tomato species. It is expected that these hybrids will have higher levels of resistance and be resistant to different begomovirus species (Moustafa % Nakhla, 1990; Vidavsky % Czosnek, 2006).
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Tobacco to tomatoes: A phylogenetic perspective on fruit diversity in the Solanaceae
Article
  • Nov 2002
The Solanaceae contains many species of agricultural importance. Several of these are cultivated for their fruits, such as the tomato, the pepper and the aubergine. The family is very diverse in fruit type with capsules, drupes, pyrenes, berries, and several sorts of dehiscent non‐capsular fruits occurring in the 90+ genera. In this paper, recent work on fruit type evolution in angiosperms is reviewed in relation to dispersal agents and habitat ecology. Defining fruit types in the Solanaceae in a simple five state system, then mapping them onto a previously published molecular phylogeny based on chloroplast DNA allows discussion of the evolution of these fruit types in a phylogenetic framework. Capsules are plesiomorphic in the family, and although berries are a synapomorphy (shared derived character) for a large clade including the genus Solanum (tomatoes and aubergines), they have arisen several times in the family as a whole. Problems with homology of drupes and pyrenes are discussed, and areas for future investigation of fruit structure homology identified. The distribution of fruit types in the large and diverse genus Solanum is also discussed in the light of monophyletic groups identified using chloroplast gene sequences. This variety is related to recent advances in the understanding of the molecular biology of fruit development. Finally, several key areas of future comparative, phylogenetic investigation into fruit type evolution in the family are highlighted.
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