Respostas morfogenéticas in vitro de açaizeiro (Euterpe oleracea Mart.) e de cupuaçuzeiro (Theobroma grandiflorum (Willd. ex Spreng.) Schum.)

Abstract

The economic potential for exploration of native fruitful species of the Amazon has increased in the last years. Among the several specie stands out the assai palm (Euterpe oleracea Mart.) and the cupuassu (Theobroma grandiflorum (Willd.ex Spreng.) Schum.), considering the several possibilities of the commercial exploration. However, the use of inadequate propagation techniques and the absence of improved genetic material have been aimed with the main problems to the economic expansion of these species. If the several tissue cultures techniques are included in genetic improvement programs, they may become a valuable instrument for the fast cloning of genotypes. The main objectives of the present work were to determine the basic methodologies for growing viable assai palm and cupuassu cultures and to evaluate the morphogenetic responses of different explants under diverse conditions of in vitro culture. The experiments were conducted in the Genetic Resources and Biotechnology Laboratory of Embrapa Amazônia Oriental, Belém, PA. The effect of the addition of growth regulators in the culture of assai palm zygotic embryos. The efficiency of two substrata was evaluated, in the presence and in the absence of MS and 1/2 MS medium, on the conversion of cupuassu embryos in seedlings. For the study of the morphogenetic capacity of assai palm explants, mature and immature zygotic embryos, rachyl segments, stem apexes, chlorophyllous young leaf segments and root apexes were used. For the cupuassu, embryonic axes and cotyledon segments of mature embryos, chlorophyllous young leaf segments, stem segments and stem apexes. The explants were cultivated in a gelled MS medium supplemented with different types and concentrations of growth regulators. The obtained results allowed verifying that an addition of NAA and BAP in the culture medium was necessary for the conversion of assai palm mature zygotic embryos into vigorous and normal seedlings. The young rachyl segments presented smaller oxidation intensity in a gelled MS medium supplemented with different antioxidants and the mature rachyl segments in a gelled MS medium with 0,3% of activated charcoal, both in the presence and in the absence of ascorbic acid. It was possible to verify the expression of a direct, repetitive and asynchronized model of somatic embryogenesis in mature zygotic embryos cultivated in primary MS medium supplemented with high concentration of 2,4-D and transferred to a secondary MS medium in the presence of NAA and 2iP. The conversion of embryos in plantlets was reached with the transfer of the cultures for 1/2 MS medium, without growth regulators. The agar and vermiculite, in the absence of culture medium, were efficient for the conversion of cupuassu zygotic embryos in normal and vigorous seedlings. The 2,4-D and TDZ promoted the formation of friable calluses in embryonic axes and in young leaf segments, respectively. KIN combined with 2,4-D promoted the initiation of friable calluses and it NAA and KIN, the rhizogenesis in cotyledon segments. In the presence of 2,4-D and KIN there was the formation of friable calluses in stem segments. The addition of coconut water, 2iP and NAA in the secondary medium stimulated the fast growth of calluses in embryonic axis, stem segments and chlorophyllous young leaves segments cultures. The obtained results show that tissue culture has a potential use for the in vitro propagation and genetic programs of assai palm and cupuassu.