Desempenho de cultivares de alface para cultivo hidropônico no verão e no inverno Summer and winter performance of lettuce cultivars grown in a hydroponic system

To select lettuce cultivars of the iceberg, crisp and butter groups, appropriate for NFT- hydroponic cultivation (NFT : nutrient film technique), two experiments were carried out, one in the summer and another in the winter. In the summer, the following cultivars were tested: Iara, Lorca, Lucy Brown, Org, and Taina (American), Brisa, Itapua, Marisa, Salad Bowl, Vera, and Veronica (crisp-head); Baba de Verao, Brazil 303, Floresta, Monalisa, Regina 440, and Vitoria de Verao (loose-leaf) and in the winter: Grandes Lagos, Iara, Kaesar, Lucy Brown, Madona, Ogr, and Taina (American); Brisa, Elba, Grand Rapids, Hanson, Itapua, Marisa, Vera, and Veronica (crisp-head); Brasil 303, Carolina, Floresta, and Livia (loose-leaf). Each experiment was installed in a randomized block design, with three repetitions. The seedlings, in phenolic foam, were transplanted 19 and 24 days after sowing in summer and win- ter, respectively, when with three or four leaves. At harvest, 46 and 63 days after sowing in the sum- mer and winter, respectively, the number of leaves per plant, stem length, fresh and dry mass of the leaves, stem, root and whole plant were determined. Salad Bowl and Veronica were the cultivars with the lowest resistance to early flowering. The most promising cultivars for summer cultivation were Iara, Lorca, Lucy Brown, Brisa, Itapua, Marisa, Vera, Brazil 303, Monalisa, and Regina 440. Those for win- ter cultivation were: Iara, Ogr, Taina, Brisa, Elba, Grand Rapids, Hanson, Itapua, Marisa, Carolina, Floresta, and Livia. Additional keywords : Lactuca sativa; cultivar; hydroponics; NFT; protected cultivation; soilless cultivation.