Microbial volatile compounds enhance drought resilience and productivity in CAM and C3 crops.

Plants interact with their associated microbiota through diverse chemical cues, including microbial volatile organic compounds (mVOCs) that act as airborne signals that modulate plant physiology and stress resilience. This is particularly relevant under drought, a major constraint on global plant productivity. Although short-term physiological responses to microbial volatiles have been widely documented, their longer-term effects on functional plant traits and performance remain poorly understood, especially in species with contrasting photosynthetic strategies and water-use characteristics. We investigated the effects of selected mVOCs-camphene (CAMP), ethyl isovalerate (EV), their combination (EV + CAMP), and nonanal-in Agave tequilana and Solanum lycopersicum cv. Micro-Tom (tomato), representing CAM and C3 species, respectively. Agave and tomato seedlings were exposed once to volatiles and then grown for eight and four and a half months, respectively, under defined water-limiting regimes. In Agave, we evaluated four groups of traits: leaf and biomass, roots, pigments and sugars and proline; whereas in tomato, we assessed growth and yield. EV followed by CAMP enhanced A. tequilana performance under moderate and severe water limitation, promoting leaf and root development, increased relative water content, as well as higher carbohydrates and chlorophyll levels. In tomato, volatile exposure increased fruit yield from 0.10 to 2.65-fold under both well-watered and moderate drought, with EV exerting the strongest effect under moderate drought. Nonanal yielded net negative effects on agaves, while the mix EV + CAMP showed positive effects on tomato, but poor results on A. tequilana. Our results demonstrate that EV and CAMP, alone or in combination, act as biologically active airborne signals that modulate plant physiological plasticity under water limitation. Remarkably, a single volatile exposure produced lasting effects on vegetative and reproductive development, highlighting their potential as sustainable tools to enhance drought resilience and crop productivity.