In vitro regeneration from leaf-base segments in three genotypes of Urochloa spp.

The key agricultural species of Urochloa P.Beauv. (signal grass), important as tropical forage grasses, are characterised by asexual seed formation (apomixis), and this presents a challenge for breeding programs. Biotechnological approaches could be an option to develop improved cultivars. We evaluated the regenerative potential from three commercial genotypes, U. brizantha cv. Marandu, U. decumbens cv. Basilisk and U. ruziziensis cv. Ruziziensis, by using leaf-base segments as explants. We tested two auxins (2,4-D and picloram) and one cytokinin (TDZ) at four concentrations (1, 2, 3 and 4 mg L-1). Seeds were scarified, peeled and disinfected before inoculation on half-strength MS media in the dark for 14 days. Leaf-base explants were sectioned in thin slices and inoculated into the media. We analysed the number of primary calluses, number of calluses with shoots clusters and the average of regenerated plants. The lowest concentration of auxins tested (1 mg L-1) yielded the highest number of regenerated plants for Marandu and Basilisk, whereas the optimum for Ruziziensis was 2 mg L-1. Medium with higher concentrations of TDZ (4 mg L-1) was required to produce high frequency of plants for all genotypes. Explants cultured on media with TDZ produced very few calluses. These results indicate that the auxins and cytokinin tested can induce plant regeneration from Urochloa leaf-base segments, and may be used to produce transgenic plants in genetic transformation studies.