The production of organically grown tomatoes in the Amazonian region of Brazil is difficult due to inherent phytosanitary issues. The objectives of the present investigation were to evaluate the productivity of grafted tomato plants (Solanumlycopersicum cv. Santa Adélia) grown organically in Rio Branco, Acre, Brazil, and to assess scion/rootstock compatibility under organic growth conditions. The Solanum species employed as rootstocks were S. gilo (jiló), S. lycocarpum (jurubebão), S. stramonifolium (jurubeba vermelha) and S. viarum (joá), while the susceptible S.lycopersicum cultivar Santa Adélia was the scion. Ungrafted tomato plants and tomato grafted on tomato rootstock were employed as controls. The experiment was arranged in a completely randomized block design with six treatments and five repetitions of five plants each. Data were submitted to analysis of variance and the significance of differences between treatments were determined using the Tukey test (P<0.05). All ungrafted tomato plants and those comprising tomato grafted on S.lycopersicum rootstock became infected by brown rot and perished. The total numbers of fruits, numbers of marketable fruits, mean masses of fruits, total productivities and productivities of marketable fruits associated with tomato grafted on S. gilo, S. lycocarpum and S. stramonifolium rootstocks were significantly higher (P<0.05) than the equivalent values obtained with tomato grafted on S. viarum rootstock. S. gilo exhibited the best compatibility index (1.11) of all rootstock/scion combinations studied. It is concluded that tomato grafted on S. gilo, S. lycocarpum and S. stramonifolium rootstocks represent viable alternatives for the production of organic tomatoes in the Amazon region.

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