Field-tested drought resilience in tomato landraces: physiological, metabolomic and genomic signatures associated with PDVIT tolerance

The Mediterranean basin is becoming increasingly exposed to intense and frequent water scarcity and increased temperatures, that are creating a critical conditions for the agricultural system. In this context, tomato plants are particularly vulnerable, as rising temperatures and prolonged drought severely impair their growth, physiological performances and yield. This study evaluated the response to drought of six indeterminate tomato genotypes (named E7, E8, E36, E40, E103 and PDVIT) selected from a collection of heat-tolerant landraces. Field trials were conducted in southern Italy under two irrigation regimes: full irrigation (100% crop evapotranspiration, ETc) and severe water deficit (30% ETc). Trials were conducted under both open-fields and plastic-tunnels. All genotypes were negatively affected by water deficit, but the extent of the physiological responses to stress varied significantly depending on the genotype and environment. Gas-exchange measurements revealed that E7 was the most sensitive to drought, experiencing an 80% reduction in net photosynthesis under both growth conditions. In contrast, PDVIT experienced only a 35% decrease in net photosynthesis while maintaining a relatively stable transpiration rate. Fruit yields were generally lower under water deficit, with E7 showing strong yield reductions of approximately 25% in open-field and 32% under plastic- tunnel compared with fully irrigated plants. PDVIT was the only landrace to maintain stable productivity across different environments and treatments. Fruit metabolomics revealed a drought-driven alteration in metabolite content in most landraces, apart from PDVIT that displayed in particularly stable sugar levels. SPET analysis showed that PDVIT had the highest number of polymorphisms with high and moderate impact in genes associated with abiotic stress responses and fruit quality. Overall, this study highlighted the landrace PDVIT as a valuable genetic resource to be used in breeding programs to produce varieties with stable yields and high-quality fruit under a climate change scenario.