Micropropagação e frio artificial no cultivo dos mirtileiros ‘Duke’ e ‘Woodard’

Abstract

The use of quality seedlings, as well as the adoption of techniques that allow the adaptation of propagation protocols and the environment for the cultivation of blueberry (Vaccinium spp.) are fundamental for the expansion of production areas. Due to these aspects, this work was divided into four experiments. In the first, the objective was to verify the influence of in vitro photoautotrophic culture, combined with the presence (or not) of sucrose in the culture medium during the multiplication of 'Duke' blueberry in two seasons. The experimental design was completely randomized, in a 3 x 2 x 2 trifactorial scheme (three sucrose concentrations (0, 15 and 30 g.L -1 ), two environments (growth room and greenhouse) and two times of the year (summer and winter)), totaling 12 treatments with 10 repetitions of five explants. After 60 days, survival, shoot length, multiplication rate, explant height and number of leaves were evaluated. In vitro multiplication of 'Duke' blueberry can be performed in a growth room and in culture medium with 15 g. L-1 of sucrose in the winter period. Of sucrose in the winter period. In the second experiment, the objective was to evaluate the vegetative growth of blueberries grown in pots under different cold conditions. The experimental design was in a 2 x 2 factorial scheme (two growing conditions (outdoor and artificial cold)) and two cultivars (‘Duke’ and ‘Woodard’)). After 90 days, the following were evaluated: length of the longest stalk, mean number of stalks, and mean length of stalks, root dry matter and root length. The different cold conditions did not influence the vegetative growth of 'Duke' and 'Woodard'. In the third, the objective was to evaluate the phenology, while the fourth experiment was carried out to evaluate the physicochemical and productive characteristics. Both trials were carried out under the same growing conditions, using the same experimental design and blueberry cultivars from the second study. Thus, in the third, the phenological stages were evaluated: yolk swelling, budding, pink initial yolk, pink final yolk, beginning of flowering, full flowering, corolla drop, fruit growth, green fruit and percentage (10%; 25% and 75%) of ripe fruits. In addition, the thermal sum of the phenological periods in two reproductive cycles was evaluated. Phenological behavior and thermal demand were influenced by the cultivation environment in the second cycle. Exposure to artificial cold is a promising technique; mainly for ‘Duke’ in the conditions of Pelotas-RS. In the last experiment, the following were evaluated: total number of fruits, total mass of fruits per plant, fresh matter mass and fruit diameter; hydrogen ionic potential, soluble solids content, titratable acidity and brix/titratable acidity ratio. It is concluded that 'Woodard' and 'Duke' exposed to artificial cold had fruits with physicochemical attributes compatible with those expected for the region. Artificial cold was efficient, especially for 'Duke' in the second crop