Duplicação cromossômica de bananeira “ouro” com amiprofósmetil e avaliação da estabilidade do conteúdo de DNA

Abstract

In banana breeding programs several of strategies are used, among them the diploid in vitro chromosomic duplication AA/BB to generate tetraploid, which posteriorly they are crossed with improved diploid allowing the creation of secondary triploids AAA/AAB, that benefit from the "gigas" effect. Therefore, the present study aims to evaluate the effect of Amiprophos-methyl (APM) in the induction of chromosomes duplication in explants of banana "Ouro", diploid cultivar that has important features for genetic improvement, as well as the genetic stability of the DNA content of the plants over 30 days. The experiment was conducted at Tissue Culture Laboratory, located in the Department of Agriculture of the Federal University of Lavras – UFLA, utilizing explants of banana “ouro” as plant material, diploid (AA), donated by EMBRAPA Mandioca e Fruticultura. Initially, the explants were established in vitro on MS medium supplemented with 2,5 mg L -1 of BAP (6-benzylaminopurine), 30 g L -1 of sucrose, 1,7g L -1 of Phytagel and pH 5,8. Completely randomized design was used with 20 treatments, consisting of the 5 different doses of APM and 4 times of exposure of explants to antimitotic, with 13 plants per plot. After the in vitro establishment, the explants were cut and transferred to a new MS medium supplemented with antimitotic APM in the following concentrations: 0, 25, 50, 75 and 100 µM, where they remained for 2, 4, 6 and 8 days. After the exposure time of the explants at APM, these were transferred to a new MS medium where they were kept until the moment of the flow cytometry analysis, performed 30 and 60 days after the last medium transfer for identifying plants with duplicated DNA content. After the flow cytometer analysis in the first reading, it was observed 204 diploids plants (78.5%), 30 mixoploids (11.5%), tetraploids 5 (1.9%) and 21 dead plants or no leaf area enough for analysis (8.1%). In analysis of second reading were observed 183 diploids plants (70.4%), 23 mixoploids (8.9%), tetraploids 4 (1.5%) and 50 dead plants or no leaf area enough for analysis (19.2%); realize a higher mortality in the exposure time of four days and at higher concentrations. Treatment of concentration 75 µM for 6 days afforded higher numbers of plants with genetic material duplicated, besides maintaining stable DNA content along the studied time.