Micropropagação da bananeira: características anatômicas, brotações múltiplas e conteúdo de DNA

Abstract

The objective was to evaluate the effect of spectral quality of light of 5 banana genotypes through the use of different colored shading nets in anatomical traits, evaluate the formation of multiple shoots and genetic stability from shoot tips of banana ‘Ouro’ in medium supplemented with high concentration of benzylaminopurine (BAP) and evaluate the performance of softwares commonly used in flow cytometry analysis, by analyzing DNA content and the coefficient of variation (CV) generated by them. For anatomical analysis, leaf segments of micropropagated seedlings of 5 banana genotypes (‘Maçã’, ‘Thap Maeo’, ‘Caipira’, ‘PA 42-44’ and ‘Princesa’) grown for 90 days under colored shading nets (white, blue, black and red) were collected. The traits evaluated were: stomatal density, stomata functionality and thickness of epidermis, hypodermis and parenchyma. The results showed that the leaf anatomy has changed with the use of colored nets and all of them, except the black net, favor the development of anatomical traits, especially the white shading net. For the analysis of multiple shoots, meristematic tips of banana ‘Ouro’ were established in vitro in tubes containing MS medium supplemented with 2.5 mg L-1 BAP, 0.1 mg L-1 AIA, 10 mg L -1 ascorbic acid, 30 g L-1 sucrose and 1.8 g L-1 phytagel. The pH was adjusted to 6.2. The tubes were left in the dark for 15 days and after for 15 days in a bright environment. After this period, the apices were subjected to treatment with two concentrations of BAP (2.5 and 22.5 mg L-1) in MS medium with all supplementation of the previous culture medium. The design was completely randomized with 15 repetitions. After 45 days the number of shoots was counted and flow cytometry analysis was made. The results showed that the explants subjected to the concentration of 22.5 mg L-1 BAP were not efficient in the formation of multiple shoots and this concentration causes loss of DNA in the explants. To verify the performance of softwares, samples were prepared for flow cytometry analysis using 25 fresh leaf segments from banana ‘NBA’. The readings were taken in flow cytometer FACSCalibur (BD) and the histograms were obtained with the CellQuest ™ software. DNA content and CV were obtained through softwares CellQuest™, WinMDI™, FlowJo™ and FCS Express™. There was no significant difference in DNA content between the different softwares, but the software WinMDI ™ showed lower accuracy in the analysis while CellQuest™, FlowJo™ and FCS Express™ were found to generate analysis more reliable.