Aluminum tolerance on genotypes of signal grass

The objective of this work was to evaluate aluminum tolerance of five genotypes of Urochloa decumbens (D24, CD24-2, CD24-27, CD24-45 e D62) and five genotypes of Urochloa ruziziensis (R30, R44, R46, R50 and R125) in hydroponic system. Uniform tillers were collected from these genotypes and transferred to two solutions: solution 1 (200 mu M CaCl2, pH 4.2) and solution 2 (200 mu M CaCl2 + 200 mu M AlCl3, pH 4.2). Twenty-one days later, the roots of the plants were separated, stained and digitalized for analysis of the length and diameter of the main root. The experiment was conducted in a completely randomized design, in factorial (genotypes x doses) with three replications. A significant interaction occurred between genotype and dose for length and width of the main root, and the results presented in average, a significant difference for most genotypes. The means of main root length in the absence and presence of aluminum were not significant for D62 (U. decumbens cv. Basilisk), CD24-45 and R46. Means were not significant for the diameter of the main root for CD24-2, CD24-27 and D62. Genotype D62 was the only one classified as tolerant to aluminum and R50 the only one classified as sensitive. Most evaluated genotypes showed medium to low tolerance. This classification was based on confidence intervals (IC 99%) for the mean of the relative tolerance indices estimated for length and diameter of the main root. These results can be used in the choice of progenitors aiming at developing segregating populations for studies of inheritance and mapping of genes and/or loci related to aluminum tolerance in Urochloa.