Establishment of an in vitro Micropropagation Protocol for Brachiaria ruziziensis.

Interest in the utilization of Brachiaria ruziziensis in no tillage crop-pasture production systems is mounting in tropical regions, because of its relatively high rusticity and foraging value. Further progress is expected towards tolerance to aluminum-toxicity and other abiotic stress conditions from ongoing breeding programs, which might become more efficient if a faster propagation procedure is provided. The purpose of this study was to contribute to such a development, by verifying the in vitro performance of two contrasting genotypes (FS03425 and FS04716) of Brachiaria ruziziensis and establishing a routine protocol for their in vitro micropropagation. Growing 10 mm-long  culm segments were excised from field-grown plants, disinfected by standard methods using ethanol/sodium hypochloride and cultured on basal 0.7% agar with MS medium, supplemented with WPM vitamins and 3% sucrose. Growth regulator (GR) and  Fe requirements were examined by varying the concentrations of BAP and IBA (respectively, 0.0; 1.0; or 2.5 µM), and by doubling or not the MS-recommended  Fe-EDTA level. Essays were carried out as a completely randomized design in a 2 (genotypes) X 2 (BAP or IBA) X 3 (GR concentration) X 2 (Fe-EDTA level) factorial, with four replications. Following a 30-day-growing period, the preliminary best results for both studied genotypes were obtained in the treatments containing  1µM BAP, 2.5 µM IBA and doubled Fe-EDTA supply. Subsequent studies are still needed to optimize plant ex vitro acclimation and also to enhance root growth so as to improve prospective in vitro examinations of tolerance to toxic aluminum.