Clonal propagation of Eucalyptus grandis using the mini-cutting and micro-cutting techniques

Abstract

O presente estudo objetivou avaliar a eficiência da propagação clonal de quatro clones de Eucalyptus grandis W. Hill ex Maiden pelo uso das técnicas de microestaquia e miniestaquia, analisando-se a sobrevivência, o enraizamento e o vigor das microestacas e miniestacas. O microjardim clonal foi constituído de microcepas oriundas de mudas rejuvenescidas por micropropagação, mediante subcultivos in vitro, e, no minijardim clonal, foram utilizadas minicepas obtidas pelo enraizamento de miniestacas oriundas de brotações de plantas propagadas pelo método da estaquia convencional. Os resultados observados para a sobrevivência após 21 ou 28 dias na casa de vegetação, enraizamento à saída da casa de sombra, sobrevivência, altura e diâmetro do colo das mudas aos 50 dias e peso de matéria seca de raízes das microestacas e miniestacas aos 28 dias, de modo geral, foram superiores na microestaquia em relação à miniestaquia. Essas diferenças foram maiores em clones com maior dificuldade de enraizamento, possivelmente, devido ao efeito de rejuvenescimento dos clones com o uso da microestaquia.

Mini-cutting and micro-cutting techniques were used to assess the clonal propagation efficiencies of four Eucalyptus grandis W. Hill ex Maiden clones. The micro-clonal hedge consisted of micro-stumps from micropropagation- derived plants produced by in vitro subcultures, whereas the mini-clonal hedge consisted of micro-stumps obtained by rooting mini-cuttings from conventional cutting method-derived sprouts. Sequential steps during cutting production from axillary shoots, after removing shoot apices, were adopted for both techniques. Micro-cuttings and mini-cuttings survival, rooting and vigor were evaluated. Survival after 21 or 28 days in the greenhouse, rooting on leaving the shade house, survival, height and root collar diameter of the cuttings at 50 days and dry weight of root matter of the micro-cuttings and mini-cuttings at 28 days, were generally higher in the micro-cuttings than in the mini-cuttings. These differences were more noticeable in clones with low rooting ability, possibly due to the effect of “rejuvenation” of the clones with the use of micro-cuttings.