In breeding programs of Brachiaria, there has been increasing interest in the early selection of desired genotypes to save time and resources. In order to allow genotype evaluation at the young seedling stage, a miniaturized in vitro growth technique was developed (based on IBA-enriched, modified MS medium) and the resulting seedlings were exposed to varying levels (4, 5 or 6 mg/L) of toxic aluminum, and compared to the controls (plots with aluminum-free nutrient solution, maintained at either pH 4, or free pH). The experiments were carried out as completely randomized design and data were statistically analyzed through ANOVA. Following a 60-day growth period, no effect was observed in the length of either the aerial part (ranging from 28 to 45 cm) or the root (ranging from 5 to 12 cm). Differences in the fresh and dry weight, on a per plant basis, of the aerial part (respectively, 2.74 to 0.94 g FW, and 0.79 to 0.23 g DW) and root (respectively, 0.62 to 0.11 g FW, and 0.030 to 0.007 g DW), albeit non-significant, revealed a clear trend of inverse association of these measures with the applied aluminum level. It is concluded that the miniaturized plant materials produced by the technique are suitable for the evaluation of aluminum toxicity under controlled conditions, on a short-term basis. Apparently, further progress might be achieved by reducing carbohydrate reserves in the plant, so that responses to the presence of aluminum in the growing substratum can be better assessed.
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