Propagação e diversidade genética de Cabralea canjerana (Vell.) Mart.

Abstract

Seedling production of canjerana has been limited by difficulty in germination, caused by recalcitrant behavior of their seeds. The objective of this study was to develop micropropagation to auxiliate preserving and multiplication of superior genotypes, to study the plantlet production by micro-cutting and mini-cutting, and to evaluate the genetic diversity of canjerana. In micropropagation, seeds of canjerana were disinfected with 0, 2.5, 5.0, 7.5 and 10% of NaOCl solution to produce aseptic seedlings, which were cultivated on MS and WPM media. Nodal segments were treated with 0 and 2.5 μM of BAP, KIN and TDZ and with 0, 1, 3, 6, 9 and 12 μM of BAP, which were cultivated on WPM media. Micro-cuttings, were cultivated on MS and WPM media with either 0 or 5.0 μM of IBA and NAA. The rooted micro-cuttings were acclimatizated in a humid chamber in a greenhouse. The highest percentage of decontaminated seeds was produced using a solution of 7.5% of NaOCl and immersion times of 10, 20 and 30 minutes. The same concentrations of BAP, KIN and TDZ and increasing concentrations of BAP in the WPM media did not increase shoot number and length. Neither the base medium nor the auxin had a significant effect on the survival of micro-cuttings after 60 days of cultivation, but the addition of 5.0 μM of NAA did increase the percentage of rooting and survival during the acclimatization. Both nodal segments and microstumps of canjerana have a low rate of multiplication. Shoots produced from microstumps may be rooted in WPM or MS medium added with 5.0 μM of NAA. These complete plantlets can be mantained in vitro or acclimatized as a source of stock plants for the microclonal hedge. For production of canjerana plantlets by mini-cutting, different concentrations of indolbutyric acid (IBA) and substrate combinations were evaluated. Mini-cuttings were treated with 2000 mg L-1 of IBA and planted in commercial substrate; coarse sand; carbonized rice husks; and a combination of the three. Apical and nodal minicuttings were treated with 0, 1000, 2000 and 3000 mg L-1 of IBA and planted in a combination of commercial substrate, coarse sand and carbonized rice husks. The productivity of microstumps and mini-cutting rooting were evaluated in three clones of canjerana. The combination of commercial substrate, coarse sand and carbonized rice husks maximized mini-cuttings rooting. Nodal mini-cuttings had higher rooting capability than apical ones. The application of 3000 mg L-1 of IBA improved rooting differentiation and growth of canjerana mini-cuttings. Canjerana clones differ in rooting capability and survival rates. The genetic diversity of canjerana, within and among progenies of three stock plants, was assessed with previously defined species-specific SSR markers. The allele frequency was calculated for each band and the heterozygosity and the polymorphic information content were calculated for each SSR pair of primers, progeny and for the combination of the 32 canjerana genotypes. The results showed high level of genetic diversity, both within and among progenies, making possible that genotypes from different stock plants grouped together. Based upon these results, high level of genetic diversity can be maintained in clones from progenies of selected stock plants.