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ABSTRACT: Effective protocols for in vitro rooting for woody fruit trees are still a challenge for in vitro seedling production, especially when there is a need to insert new cultivars or rootstocks. These protocols are essential to accelerate studies in plant breeding programs and for seedling distribution. This study evaluated the use of 6-Benzylaminopurine (IBA) in in vitro rooting of Pyruscomunnis rootstocks, clones ‘OHxF87’ and Pyrodwarf. Explant exposure times (0, 24, 48, 72, and 96 hours) to 20 mg L-1 IBA were tested for in vitro rooting. The exposure to IBA resulted in rooting rates above 80%, surpassing some results reported in the literature. The 24-hour treatment provided 81,81% survival, leading to an average growth of five roots with 19 mm length, for ‘OHxF87’ rootstock. The same exposure time resulted in the highest survival rate (75%) and the highest mean root number, seven roots per plant with 10 mm length, for ‘PDW’ rootstock. Root formation did not occur in the absence of synthetic auxin. Therefore, it can be concluded that a 24-hour exposure at 20 mg L-1 IBA was sufficient to promote in vitro rooting in ‘OHxF87’ and Pyrodwarf rootstocks’.

ABSTRACT: The objective of the research was to evaluate cytokinin concentrations and agricultural residues as physical structuring agents of the culture medium in the in vitro propagation of highbush blueberry (Vaccinium corymbosum ‘Duke’). To that end, three different concentrations of 2-isopentenyladenine (2iP) (0, 5, and 10 mg L-1)in woody plant medium (WPM) and five structuring agents (in natura rice husks, carbonized rice husks, coconut fiber, S-10 Beifort®, and agar)were tested. After 60days of culture, the following parameters were evaluated: survival (%),sprout and shoot lengths (cm),propagation rate, number of sprouts, and shoot dry mass (g). The substrates used as structuring agents were analyzed in terms of pH and electrical conductivity. The in natura rice husk, S-10 Beifort®, and carbonized rice husk did not differ from the agar in terms of the sprout length. The shoots were longer (1.64 cm) in cultures within natura rice husk than in other treatments. In the absence of 2iP, S-10 Beifort® resulted in the highest propagation rate (2.97). Concerning the number of sprouts, S-10 Beifort®, in natura rice husks, and carbonized rice husks did not differ from agar. However, when the regulator was added, the agar performed better in comparison to the other residues. Thus, in natura rice husks, carbonized rice husks, and S-10 Beifort®are potential physical structuring agents of the culture medium that can be used without 2iP.

An adequate concentration of growth regulators as well as the replacement of agar by an alternative medium may be promising from practical and financial points of view to produce orchid plants by micropropagation. The objective of this work was to evaluate different concentrations of growth regulator and alternative substrates for agar replacement in culture medium for in vitro multiplication and rooting of Oncidium baueri. In the explant multiplication phase, two experimental factors were evaluated- various concentrations of 6-benzylaminopurine (BAP) (0.0, 1.0, 2.0, and 3.0 mg L-1) and substrates (agar, vermiculite, and coconut fiber) added to MS medium. In the rooting phase, different concentrations of indole butyric acid (IBA) (0.0, 0.5, 1.0, and 1.5 mg L-1) were added to culture medium containing the same substrate. Six months after the experiments were initiated, the survival percentage, number of leaves, shoots, and roots and length of the aerial part and the major root were evaluated. The results suggested that addition of 1.0 mg L-1 BAP is necessary for the O. baueri in vitro multiplication phase, but IBA is not necessary in the rooting phase. For the substrate, vermiculite is not indicated as an agar replacement. In contrast, coconut fiber can be used in both multiplication and rooting phases of Oncidium baueri in vitro culture.