Propagação in vitro, aclimatização e produção de orquídea Oncidium baueri Lindl. em sistemas de cultivo sem solo

Abstract

The brazilian orchid Oncidium baueri is sold as cut flowers, potted plant or to compose landscape projects with high profit returns to the grower. Micropropagation is a marketable and ecological alternative to obtain orchid plants because it provides genetic gains in clonal populations, in addition to produce a large number of healthy and high quality plants in small areas and short period of time. Concerning the production of adult plants, the available information on the adaptation of this species to different cropping systems in the state of “Rio Grande do Sul” are scarce. A promising alternative to pots filled with substrate growing system may be the adoption of hydroponic system, especially to target cut flower market or the production of bare root transplants. Addressing these issues, a research work was conducted in the “Departamento de Fitotecnia/FAEM/UFPel”, located in Capão do Leão, RS and it was formalized in three articles, described below. Article 1 studies different plant growth regulator concentrations and alternative substrates for agar replacement in culture medium for O. baueri in vitro multiplication and rooting. In the explants multiplication phase, two experimental factors were evaluated: benzylaminopurine concentration (BAP) (0.0, 1.0, 2.0 and 3.0 mg.L- 1) and substrate (agar, vermiculite and coconut fiber) added to MS medium (MURASHIGE and SKOOG, 1962); and, in the rooting phase, indole butyric acid concentrations (IBA) (0.0, 0.5, 1.0 and 1.5 mg L -1) used in the same previous substrates and culture medium. It was found that for O. baueri in vitro multiplication phase BAP addition at the concentration of 1.0 mg l-1 is necessary, but in rooting phase AIB use is not necessary. Concerning the substrates, vermiculite is not indicated for agar replacement. On the other hand, coconut fiber can be used in both multiplication and rooting phases of O. baueri in vitro culture. Article 2 focus on substrates based on agricultural residues for acclimatization of O. baueri [S-10Beifort®; carbonized rice husk (CAC); coconut fiber (FC); S-10Beifort® + CAC, at the ratio 1:1 (v/v); S-10Beifort® + FC, at the ratio 1:1 (v/v); and CAC + S-10Beifort® + FC at the ratio 1:1:1 (v/v/v)]. The following variables were evaluated: survival percentage; plant aerial part height, leaves, sprouts and roots number and highest root height. There 12 were no statistical differences among substrates for all evaluated variables, with an average survival percentage of 30%. Although no significant differences among substrates for all variables were found, considering the ease of preparation and the availability for the southern region of Brazil, the S- 10Beifort® can be considered a promise alternative substrate for the acclimatization of O. baueri. Lastly, Article 3 reports research on vegetative development of O. baueri in two soilless cultivation systems (pots containing substrate and NFT hydroponic system). Plant aerial part height, pseudobulb diameter and number of sprouts were monthly evaluated. Dry mass of aerial part and roots were evaluated 11 months after experiment setting. The obtained results indicated that the cultivation system in pots containing substrate provided O. baueri higher vegetative growth and development than NFT hydroponic system. The differences between the systems appear in the fifth month (April) for plant height, and in the eighth month of cultivation (July) for number of sprouts. In front of this, further studies must be conducted to test other variants of the system.