Experimental design and growing conditions

During the years 2020 and 2021, experiments were conducted in three different environments: (i) climate chamber (first year), (ii) greenhouse (second year), and (iii) open field (second year). The adopted workflow is presented in Figure 1 . The plant material was Solanum lycopersicum. The Micro-Tom cv. was grown both in climate chamber and greenhouse, while Rio Grande cv. in the open field.

Workflow adopted to assess the effects of a biostimulant in controlled environments and open field. The main steps are briefly described. The first step includes phenomic and transcriptomic analyses conducted in the laboratory and the evaluation of agronomic traits. The last step is the validation of the observed biostimulant effects in the greenhouse and field.

A biostimulant product based on one extract of the brown alga Ascophyllum nodosum (ANE) provided by Sipcam Oxon S.p.A. (Pero, Italy) was applied as a foliar spray. The chemical composition is reported in Table 1 . We tested different doses of seaweed extract obtained by serial dilutions (from 1:10000 to 1:100) to identify a range of optimal product efficacy in terms of the promotion of plant biomass and fruit yield. These preliminary experiments (data not shown) permitted the selection of two ANE doses: 1 or 2 l ha^-1. Foliar applications were repeated three times during the reproductive phase at the specific stages: BBCH51 (first inflorescence visible, first bud erected), BBCH61 (first inflorescence: first flower open), and BBCH65 (five or more inflorescences with open flowers) (Meier, 2001).

Ascophyllum nodosum extract (ANE)-based biostimulant composition, provided by Sipcam Oxon S.p.A. .