Molecular tools and consumer taste converge to reshape semi-arid tomato breeding

Tomato is one of the world’s most important vegetable crops, and a newly published review argues that breeding it for the future—especially in semi-arid regions—will require weaving together three threads that have too often been treated separately: the crop’s genetic diversity, the sensory preferences of the people who buy and eat it, and a fast-moving toolkit of molecular breeding and genome-editing technologies. The review, published in Discover Plants, synthesises existing literature on genetic, molecular and market-aligned breeding solutions for climate-resilient tomato production, with a particular eye on regions where elevated temperatures, water scarcity and erratic rainfall progressively constrain productivity and yield stability.

The scale of the crop explains the stakes. According to figures cited in the review, annual global tomato production is approximately 161 million tons grown on about 4.8 million hectares, with per capita supply of around 20.9 kilograms per year. Asia leads production, contributing 63.8 percent of the global total, followed by the Americas at 12.5 percent, Africa at 12.31 percent and Europe at 10.9 percent. Those regional contrasts matter, the authors note, because semi-arid areas of Africa face lower productivity, drought and low resilience, underscoring the need for cultivars that can hold yields together under stress. Water stress reduces cell expansion and photosynthetic efficiency, while high temperatures disrupt fruit set and quality, reducing yield potential.

A central theme of the review is the paradox at the heart of cultivated tomato genetics. Domestication and subsequent improvement produced a considerable reduction in genetic diversity: repeated selection for large fruit size, uniform ripening and higher yield narrowed the genetic base of cultivated tomatoes, and the domestication bottleneck followed by intensive modern breeding removed many potentially valuable genes associated with stress tolerance, disease resistance and environmental adaptation. Wild tomato species and traditional landraces, by contrast, remain reservoirs of variation, carrying beneficial alleles for drought tolerance, heat stress, pest and disease resistance, and fruit quality traits that may have been lost along the way. Species such as Solanum pennellii and S. habrochaites contribute adaptive traits including vigorous root growth, reduced water loss and superior leaf thermoregulation. The review identifies genetic erosion—the widespread cultivation of a limited number of elite cultivars and the gradual loss of traditional landraces—as a continuing concern for future crop improvement.

Molecular markers are presented as the indispensable instruments for putting that diversity to work. The review classifies markers into PCR-based, hybridization-based and sequence-based categories, each with distinct advantages and limitations. Early hybridization-based systems such as restriction fragment length polymorphisms offer high reproducibility and co-dominant inheritance but are laborious, time-consuming and demand large quantities of high-quality DNA. PCR-based markers including RAPD, ISSR, AFLP, SCAR, SRAP and SSR improved throughput and reduced DNA requirements, though they differ markedly in reproducibility: RAPD and ISSR markers are fast and cost-effective for preliminary diversity surveys but suffer from dominant inheritance and sensitivity to reaction conditions, while simple sequence repeats, with their multi-allelic nature and co-dominant inheritance, have become robust tools for cultivar fingerprinting, genetic structure studies and germplasm management.

The emphasis has now shifted decisively toward single nucleotide polymorphisms, which offer unparalleled genome-wide coverage. Falling sequencing costs have enabled high-throughput SNP discovery, facilitating genome-wide association studies and genomic selection. Although SNPs are typically less informative per locus than SSRs, their high density and genome-wide distribution compensate when dense coverage is needed for predictive breeding. The review also highlights newer platforms: Kompetitive Allele-Specific PCR assays, a fluorescence-based genotyping method offering high accuracy and cost-effectiveness for large breeding populations; genotyping-by-sequencing, which combines genome complexity reduction with next-generation sequencing to discover and genotype thousands of SNPs without prior marker development; and next-generation sequencing approaches, including whole-genome and RNA sequencing, which have expanded the discovery of genes controlling drought tolerance, heat tolerance and fruit quality.

On the consumer side, the review stresses that acceptance is determined by a combination of external attributes—fruit size, shape and colour—and internal quality traits such as flavour, texture and nutritional composition, shaped by individual sensory perception and previous consumption experience. Producers, by contrast, generally prioritise resistance to biotic and abiotic stresses, high yield potential and ease of harvesting. Studies in some semi-arid regions suggest consumers there place greater importance on fruit firmness, shelf-life and overall quality, because limited water availability, high temperatures and variable market access can spread postharvest losses. Other consumer groups favour juiciness and sweetness for fresh consumption, while home processors prefer higher dry matter content. The review describes sensory clustering—grouping consumers by shared preference profiles using multivariate techniques such as principal component analysis, hierarchical clustering and preference mapping—as a way to link measurable fruit quality traits to purchasing decisions and feed them into breeding objectives alongside market demand from fresh and processing chains.

For stress tolerance itself, the review surveys a layered set of approaches. Marker-assisted selection leverages DNA markers near genes of interest, allowing precocious identification of superior genotypes from juvenile plants and mitigating environmental confounding. Genomic selection complements conventional breeding by using dense genome-wide markers to predict breeding values for complex traits such as yield, quality and stress tolerance, and in semi-arid environments it facilitates identification of breeding lines carrying favourable alleles for water-use efficiency, heat tolerance and nutrient-use efficiency. Drought-tolerance genes such as ShDHN, SlDREB2 and SlLBD40, which bolster osmotic adjustment and water-use efficiency during extreme deficits, are highlighted as valuable targets. Transcriptomic profiling adds another layer: RNA-seq analyses of drought-stressed tomato plants have revealed upregulation of late embryogenesis abundant proteins, DREB transcription factors and antioxidant-related genes contributing to osmotic adjustment and oxidative stress protection. The review is candid about the limits of transcriptomics, however—gene expression reflects mRNA abundance at a specific time and condition and does not necessarily reflect enzyme activity or the resulting phenotype, so functional validation through overexpression studies, qRT-PCR, RNA interference or targeted mutagenesis remains vital before candidate genes enter breeding programmes.

Genome editing emerges as the review’s most transformative technology. CRISPR/Cas9 permits site-specific alteration of native tomato loci governing abiotic stress resilience, yield homeostasis and disease resistance without integrating foreign DNA, distinguishing it from transgenic approaches, which introduce beneficial genes from external sources but face regulatory challenges and public concerns. Concrete examples cited include CRISPR/Cas9-mediated editing of the SlAGL6 gene, which resulted in improved fruit set and reproductive stability under elevated temperatures, and mutants of SlLBD40 and SlARF4 that exhibited sustained drought tolerance after prolonged irrigation withdrawal, pointing to auxin-mediated regulatory pathways in maintaining plant water status. Edited lines targeting heat shock factors and heat shock proteins showed improved protein folding capacity, maintained photosynthetic activity and improved fruit set under high-temperature conditions. The review also compares editing platforms: ZFNs and TALENs display high specificity but require extensive protein engineering for each target, while CRISPR/Cas9 simplifies target design through guide RNAs, though it remains constrained by PAM sequence requirements, off-target mutation risk and genotype-dependent transformation efficiency. Newer tools—high-fidelity Cas variants, base editing, prime editing and CRISPR/Cas12a—reduce many of these limitations. Regulatory frameworks differ sharply, with some regions treating gene-edited crops without foreign DNA leniently while others, such as the EU, categorise them alongside GMOs.

Speed breeding rounds out the integrated pipeline the review envisions. By optimising controlled environments—extended photoperiods of 20 to 22 hours with high-intensity LED lighting, photosynthetic photon flux densities of 300 to 500 µmol m⁻² s⁻¹, daytime temperatures of 24 to 26 °C and relative humidity between 50 and 70 percent—tomato generation time can be reduced from roughly 90 to 120 days under conventional greenhouse conditions to approximately 55 to 70 days, allowing up to six generations annually. These reductions have been consistently demonstrated under controlled-environment protocols. The review reports that programmes at the John Innes Centre in the UK and the University of Sydney in Australia have applied speed breeding to solanaceous crops, releasing pre-commercial heat- and drought-resilient hybrids three to four times faster, and that heat-tolerant tomato lines incorporating wild-relative introgressions from S. pimpinellifolium were developed and field tested in two to three years versus eight to twelve years conventionally. The authors caution that speed breeding requires considerable investment in specialised infrastructure, constraining adoption in resource-limited programmes.

The review’s conclusion is that no single technology suffices. It proposes an integrated research roadmap: combining transcriptomics, proteomics, genomics and phenomics to identify robust biomarkers and regulatory networks; functionally validating candidate genes with genome editing and field-based studies; strengthening high-throughput phenotyping of canopy temperature, water-use efficiency and root architecture; broadening the genetic base through systematic use of wild relatives including S. pennellii, S. chilense, S. pimpinellifolium and S. peruvianum; and conducting extensive multi-environment field trials in semi-arid and climate-vulnerable regions. Notably, the authors acknowledge that although several genome-edited tomato lines have demonstrated improved drought and heat tolerance under controlled greenhouse and growth-chamber conditions, relatively few have undergone extensive multi-location field evaluations, and broader multi-season, multi-environment trials are still required before large-scale commercial deployment. Artificial intelligence, digital phenotyping and pangenomics— which capture structural variants and novel genes absent from the reference genome—are flagged as the next frontier. The unifying message is that climate-resilient tomatoes will succeed only when agronomic performance, genetic diversity and the preferences of farmers, consumers and markets are bred together rather than apart.

Subject of Research: A review of genetic diversity, molecular breeding tools and consumer preferences for developing climate-resilient tomatoes in semi-arid regions.

Article Title: Unveiling genetic diversity and consumer preferences of tomato (Solanum lycopersicum L.) in the semi-arid regions

Article References: Teresia, K. N., Chukwu, S. C., Nanhapo, P. I., & Maliata, W. A. (2026). Unveiling genetic diversity and consumer preferences of tomato (Solanum lycopersicum L.) in the semi-arid regions. Discover Plants, 3(1), Article 503. https://doi.org/10.1007/s44372-026-00983-5

Image Credits: AI Generated

DOI: 10.1007/s44372-026-00983-5

Keywords: tomato, genetic diversity, molecular markers, CRISPR-Cas9, drought tolerance, heat tolerance, speed breeding, semi-arid agriculture, consumer preferences, genomic selection, transcriptomics, food security