Rizogênese in vitro, aclimatização e desempenho inicial a campo de plantas micropropagadas e tolerância in vitro de genótipos de açoita-cavalo (Luehea divaricata Mart. & Zucc) ao alumínio

Abstract

Originating in South America, the açoita-cavalo (Luehea divaricata Mart. & Zucc.), is a native species that makes up the Pampa and Mata Atlântica biomes, and that has shown a reduction and fragmentation of its natural populations. It has relevant characteristics in its wood, mainly for use in bending techniques, and for this reason this species over a long period suffered an intense exploitation that drastically reduced its specimens in Rio Grande do Sul. Thus, in view of its great silvicultural, ecological and economic importance, it is justified to carry out studies related to guarantee its perpetuation via seedling production. For this to occur, studies related to the production of seedlings are necessary, through micropropagation, which was done in the following work. In view of the above, the present study aimed to evaluate the stages of rhizogenesis in vitro and acclimatization in vitro and ex vitro of the micropropagation of açoita-cavalo, its initial performance in the field, as well as checking the in vitro tolerance of aluminum genotypes, and, for that, the different nutritional means were initially evaluated (MS, MS/2, WPM or WPM/2) in the stage of in vitro rhizogenesis of shoots of açoita-cavalo. Then, the effects of adding Indolbutyric Acid (IBA) to the in vitro rooting of the species to the MS nutrient medium were studied. The effect of the culture medium as a function of the volume of nutrient medium associated with vermiculite in the in vitro rhizogenesis of açoita-cavalo.The results obtained indicate that the MS nutrient medium is more efficient for the development of horse whipping in the rhizogenesis phase in vitro, reaching values of 62.50% in the formation of primary roots. The use of IBA in the stage of in vitro rhizogenesis can be dispensed with, however the presence of auxin in concentrations up to 20μM improves the quality of the root system. The volume of 20 mL of nutrient medium associated with 30 cm³ of vermiculite is efficient for rhizogenesis in vitro. In the acclimatization phase, both in vitro and ex vitro, the use of IBA may be dispensed with, however performance improves with supplementation of up to 20 μM of auxin. Considering the effect of AIB, it is necessary to extend the acclimatization period to 80 days, including the steps of 20 days in in vitro conditions and an additional 60 days in a greenhouse. The volume of 20 mL of nutrient medium associated with 30 cm³ of vermiculite is efficient in acclimatization in vitro and ex vitro and considering the effect of the culture medium only, it is necessary to extend the acclimatization period to 90 days, including the steps of 30 days in vitro conditions and 60 additional days in a greenhouse. The initial performance of micropropagated seedlings of açoita-cavalo is evident in just 30 days and registers a high average of survival, increase in diameter and increase in height for both seedlings from the effect of IBA and the effect of the culture medium. Finally, in the in vitro establishment and rhizogenesis phase, the açoita-cavalo shows tolerance to aluminum, being able to survive, resume growth and form primary roots, even with limitations in its development.