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Fig. 1. Procedure to identify acid soil-adapted Brachiaria genotypes. Plants were propagated in a mixture of soil and sand (3:1). Vegetative propagules (stem cuttings), excised from these plants, were floated at the surface of a low-ionic-strength nutrient solution to produce adventitious roots. After 9 d, pairs of rooted stem cuttings were selected for homogeneity. One propagule of each pair was transferred to Solution 1 (200 µM CaCl2, pH 4.20), the other to Solution 2 (200 µM CaCl2, 200 µM AlCl3, pH 4.20). Twenty-one days after transfer, roots were separated from stems, stained, and scanned on a flatbed scanner to determine total root length (RL) and average root diameter. Genotypes with vigorous root growth were identified based on RL in Solution 1. Aluminum-resistant genotypes were identified based on RL in Solution 2 after removing the variance component that was due to differences in root vigor measured in Solution 1.
