Tomato (Solanum lycopersicum L.) is an economically important crop worldwide, particularly in tropical and subtropical regions. However, production is significantly and increasingly affected by the impacts of climate change, including heat and drought stress and emerging pests and diseases. This study specifically evaluated the effects of heat stress on root and shoot morphology, photosynthesis, and yield traits in five tomato genotypes, to identify the characteristics that differentiate heat tolerance from susceptibility. Heat stress experiments were conducted in a polyhouse, one during the summer under high temperatures, with a non-stress trial during the winter under conducive natural conditions. Significant reductions in yield, root traits and photosynthesis were observed across all genotypes under heat stress. However, the genotype MG785-1 maintained a relatively higher yield (298.01 ± 25.1 g), a 37.7% reduction compared to non-stress conditions, while CLN4786F1 showed resilience with a 32.3% decrease compared to its non-stress harvest index. Root dry weight (5.91 ± 0.53 g in MG785-1) and root shoot ratio (0.19 ± 0.01 in MG785-1) were identified as key traits for heat tolerance. Physiological traits, such as photosynthetic rate (11.71 ± 1.61 µmol CO₂ m⁻² s⁻¹ in MG785-1), were critical for maintaining growth under heat stress. In contrast, the heat-sensitive genotype CLN3961D exhibited a significant decline in yield and physiological performance. Root dry weight and root to shoot ratio were key indicators for heat tolerance, while the photosynthetic rate was critical for maintaining plant growth under stress. These findings underscore the importance of integrated root and physiological traits, providing valuable insights for breeding climate-resilient tomato varieties.

Background: High temperature severely limits tomato reproductive development and yield, particularly in tropical production systems. Pollen viability and fruit set are commonly used as indicators of reproductive heat tolerance, but much of the supporting evidence has been obtained under controlled conditions. Their relevance to breeding under variable open-field environments remains less clear. This study investigated reproductive performance and its genetic basis under open-field heat stress using a multi-parent advanced generation inter-cross (MAGIC) population. Results: We developed a MAGIC population from eight Solanum lycopersicum parents combining heat tolerance and multiple disease resistances and evaluated 262 F _5:6 lines under natural open-field heat stress. Flower number showed the highest heritability (0.64), followed by pollen viability (0.56), fruit number (0.48), and days to flowering (0.25), whereas fruit set showed negligible heritability (<0.01). Despite its moderate heritability, pollen viability was only weakly correlated with fruit set ( r = 0.22). In contrast, fruit number was strongly correlated with fruit set ( r = 0.86), supporting fruit number as a practical selection criterion for reproductive performance under open-field heat stress. Restriction enzyme-associated DNA sequencing generated 16,350 high-quality SNPs for genome-wide association analysis, which identified multiple QTLs for reproductive traits, several overlapping previously reported loci. A region on chromosome 6 at approximately 31–33 Mb was particularly notable because it was associated with multiple reproductive traits and coincided with a previously reported heat-responsive QTL region. Candidate-gene analysis highlighted floral developmental regulation, represented by positional candidates SlAGO7 , ENO , and SlWUS , and cellular and protein homeostasis, supported by direct candidates including MON1, ECM29, and ubiquitin-related genes. Conclusions: Selection criteria established under controlled environments may not fully predict reproductive performance under open-field heat stress. Fruit number provides an integrative and moderately heritable indicator of realized reproductive success under field conditions. The identified QTLs and candidate genes provide targets for validation and development of heat-tolerant tomatoes adapted to tropical open-field production.

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.

Tomato (Solanum lycopersicum) is an essential vegetable crop cultivated worldwide, but its production is highly vulnerable to tomato yellow leaf curl disease (TYLCD), which is transmitted by whiteflies (Bemisia tabaci). Management strategies typically focus on controlling either the virus or its vector. This study evaluates the effectiveness of multi-disease and insect-resistant tomato lines, developed by the World Vegetable Center (WorldVeg), which integrate Ty-1/Ty-3 genes for virus resistance and WF2-10 and WF3-09 genes for whitefly resistance. Virus accumulation, whitefly settling behavior, and adult mortality were assessed among multi-resistant lines, a Ty-resistant line, a whitefly-resistant line, and a susceptible check using preference bioassays, controlled inoculation experiments, and acylsugar quantification. Multi-resistant lines exhibited significantly higher acylsugar concentrations, reduced whitefly preference for settling, and increased whitefly adult mortality. Additionally, these lines displayed less severe disease symptoms and lower virus accumulation over time than Ty-resistant, whitefly-resistant, and susceptible controls. These findings highlight the superior efficacy of combined virus and vector resistance in mitigating tomato yellow leaf curl Thailand virus (TYLCTHV) transmission. This research underscores the importance of integrated genetic resistance as a key element of sustainable integrated pest management strategies, offering an environmentally friendly solution for safeguarding global tomato production.

Tomato (Solanum lycopersicum L.) is economically important worldwide, particularly in tropical and subtropical regions, and production is significantly affected by climate change, notably heat stress. This study evaluated the effects of heat stress on root and shoot morphology, photosynthesis, fruit set, and yield traits in five tomato genotypes to identify the characteristics that differentiate heat tolerance from susceptibility, which will enable us to identify sources for key traits for breeding. The heat stress experiment was conducted during the summer under naturally high temperature conditions in a polyhouse, while a non-stress trial was conducted during the winter under permissive natural conditions in a polyhouse. Significant differences were observed between the trials and among genotypes, with heat tolerant MG785-1 and CLN1621L demonstrating superior root system architecture, greater leaf area and better physiological performance compared to the susceptible genotype CLN3961D. Root dry weight and root to shoot ratio were key indicators for heat tolerance, while the photosynthetic rate was critical for maintaining plant growth under stress. These findings highlight the importance of strong root systems and effective photosynthesis for heat tolerant tomato, providing new insights into improving crop resilience for regions affected by climate change.

Bacterial wilt (BW), caused by members of the Ralstonia solanacearum species complex (RSSC), is a devastating disease affecting many crops, including tomato. Among the management practices implemented to combat BW, developing host resistance is the most effective approach. Therefore, it is crucial to identify sources of resistance within the available tomato germplasm. In this study, we evaluated 10 tomato lines from the World Vegetable Center in Taiwan, each possessing either the Bwr-6-linked or the Bwr-12-linked marker gene for BW resistance. We used two RSSC strains in our experiments: phylotype I strain NG-RL01 and phylotype II strain K60, both isolated from North Carolina. The two independent experiments were conducted simultaneously in a greenhouse using a split-plot design with six replications. Five-week-old plants were drenched and inoculated in the wounded root zone with a suspension of a 2-day-old bacterial culture. Disease severity was assessed daily using a standard disease rating scale, and the area under the disease progress curve was calculated. The results showed significant differences between the two bacterial strains, the tomato lines, and their interactions. Furthermore, K60 was more aggressive than NG-RL01. Most of the tomato lines were resistant to strain NG-RL01; however, none of the tested lines showed resistance to strain K60. Interestingly, a few plants, specifically AVTO2102, showed some resistance to K60. The findings indicate that the BW resistance-linked markers Bwr-6 and/or Bwr-12 confer considerable resistance to strain NG-RL01 but are ineffective against strain K60, emphasizing the need for research to enhance resistance across different RSSC strains. [ ] Copyright © 2026 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .