Optimization of somatic embryogenesis and in vitro plant regeneration of Urochloa species using picloram

The establishment of an efficient methodology for regeneration in Urochloa spp. via somatic embryogenesis is an essential component of genetic engineering technology. The aim of this study was to evaluate different concentrations of growth regulators on callus induction, somatic embryogenesis, and plant regeneration of Urochloa spp. using mature seeds as the initial explant. Firstly, different concentrations (1, 2, 4, and 8 mg/L) of 2,4-D or picloram were tested using U. brizantha cv. Marandu. In a second step, the above concentrations of picloram were also used to evaluate its effect on the morphogenetic potential in different genotypes: U. brizantha cvs. Xaraés and Piatã, U. decumbens cv. Basilisk, U. humidicola cv. Llanero, and U. ruziziensis cv. Ruziziensis. There was no significant difference between concentrations of 2,4-D or picloram for the production of primary calluses in U. brizantha cv. Marandu, ranging from 58.5 to 69.2%. However, embryogenic calluses induced under picloram showed higher percentage of shoot formation after transferring to MS medium with 2 mg/L BA. A higher number of shoots were produced in mature seed cultures of U. decumbens cv. Basilisk and U. brizantha cvs. Marandu and Xaraés supplemented with 1 mg/L picloram. No albino plants were regenerated using picloram. The successful regeneration of green and morphologically normal plants opens the possibility of using this protocol to obtain transgenic plants in Urochloa spp.