Performance morfofisiológica e agronômica do tomateiro sob diferentes regimes hídricos e tratados com Rhizophagus intraradices e Pseudomonas fluorescens

Abstract

Water scarcity is one of the main limiting factors for tomato (Solanum lycopersicum L.) production, especially during flowering. In this context, understanding the mechanisms of tolerance to water deficit exhibited by tomato plants becomes essential to mitigate the effects of drought, as well as the use of technologies such as bioinputs that help plants cope with adverse environmental conditions. The underlying hypothesis is that controlled levels of water deficit over a given period induce distinct physiological, biochemical, morphological, and yieldrelated responses, reflecting the plant's adaptive adjustments under different intensities of stress. Additionally, it is assumed that individual or combined inoculation with Rhizophagus intraradices and Pseudomonas fluorescens may lessen the effects of water limitation in tomato plants. The studies were conducted in a greenhouse with the hybrid Momotaro Paz (TAKII SEED), with the objectives of: (i) assessing the biochemical, physiological, and agronomic response of tomato plants grown under controlled levels of water deficit (equivalent to 0, 25, 40, and 50% water restriction) for 10 days (Chapter 1); and (ii) testing the effect of separate and combined inoculation of R. intraradices and P. fluorescens on the response of tomato plants subjected to water deficit (Chapter 2). The first experiment followed a randomized block design with four treatments and five replications. The second experiment used a randomized block design in a 2 x 4 factorial arrangement (water levels – with and without stress x non-inoculated, inoculation with P. fluorescens, inoculation with R. intraradices, and co-inoculated P. fluorescens and R. intraradices), with six replications. Analysis of variance was performed for all parameters, followed by Tukey's test at the 5% probability level in both experiments. A 50% water deficit reduced plant height and stem diameter, the number of flowers and fruits, the fruit mass and diameter, increased the number of fruits with black bottom-end rot. It also altered physiological indicators such as the reduction in CO₂ assimilation rate, relative water content, starch, chlorophyll and carotenoid levels, and the increase in electrolyte leakage and proline and soluble sugar contents. The 25% water restriction level showed few differences compared to the control (0%), suggesting tolerance up to 25% during the 10-day period. In the second experiment under deficit conditions, inoculation with P. fluorescens increased the number of flowers, clusters, and fruits, while inoculation with R. intraradices promoted plant growth. Both, microorganisms individually, positively influenced fruit mass and diameter, maintained the relative water content, and lower electrolyte leakage. Co-inoculation produced intermediate effects, with greater sensitivity in some parameters. It is concluded that water management combined with microbial inoculation is a practical and sustainable alternative to reduce yield losses in tomato production under low soil availability