HARVEST PERIOD AND PRODUCTION OF TOMATO (Solanum lycopersicum L.) GRAFTED AND PRUNED TO MORE THAN ONE STEM, GROWN UNDER GREENHOUSE CONDITIONS

Grafted tomato (Solanum lycopersicum L.) plants can be pruned to more than one stem, and therefore knowing if the observed growth responses are triggered by rootstock or pruning method is a matter of interest. The aim of this work was to study the effect of grafting and number of stems per plant on its phenological and productive behavior. Two greenhouse trials were carried out under a 24x40 m metallic greenhouse with parabolic roof in La Plata, Buenos Aires, Argentina (33 degrees 56'42,6"S, 60 degrees 33'35,6"W), evaluating: 1) Plant: non-grafted 'SVTH 2900', self-grafted, grafted on 'Multifort'; 2) Stems per plant: one, two, four. The experimental design was a randomized complete block with a 2x3 factorial arrangement with 3 replications (2020), and a 3x3 factorial arrangement with 4 replications (2021). Number of days and accumulated degree days from transplant as well as yield and average weight of fruits were recorded. Data were analyzed using an analysis of variance and Tukey's test. No differences were observed at the beginning of the harvest, while the productive cycle was prolonged by grafting and greater number of stems. Grafting increased the average weight of fruits, total yield by 32-34%, and the production of fruits weighing >150 g by 45%. Total yield was promoted in plants with two stems. In addition, the number of fruits was higher in plants with two stems in 2020, and increased in grafted plants with four stems in 2021. Under the trial conditions, the use of grafted tomato plants and plants with two stems is recommended since a better phenological and productive behavior is observed.