The objective of the present study was to assess the influence of the exposition time to rooting medium on the in vitro and ex vitro growth of banana plants. As explants, new axillaries buds obtained from the in vitro establishment and multiplication of stem apices of Caipira (AAA), Preciosa (AAAB) and Japira (AAAB) cultivars were used. The MS medium with reduction to 50% of the salt concentration adding 30 g.L-1 of sucrose, 1 mg.L-1 of IBA, and 6 g.L-1 of agar was used to induce rooting. The treatments were analyzed in a 3x4 factorial design, with three cultivars (Caipira, Preciosa and Japira) and four in vitro rooting periods (7, 14, 21 and 28 days), given a total of 12 treatments. At the end of each period, the height of the aerial portion, and number and length of roots were assessed, and the plants were submitted to 90 days of acclimatization. After that, the survival, number and length of roots, pseudostem diameter, and dry weight of the roots, aerial and total portions of the plants were assessed. Generally, the root induction step in the in vitro banana budding occurred up to 14 days of cultivation in rooting medium, and after that, the roots grew only in length. Among the cultivars, it was verified that, with the exception of the pseudostem diameter, the Caipira cultivar showed superior in vitro vegetative growth, and during the acclimatization, the height of the plant, number and length of the roots, and dry mass of the aerial, roots, and total parts, were also superior to the observed in Preciosa and Japira cultivars. After 21 days on rooting medium, the survival rate of the plants in greenhouse reach 100%, in despite of the tested cultivar.
Musa spp.; micropropagation; ex vitro establishment; root system; genotype
