Effect of Aluminum Toxicity on Root Growth and Morphology of Common Bean (Phaseolus vulgaris L.) Genotypes

Aims: To investigate the effect of aluminium on root growth, morphology and the concentration of aluminium in the root tissues of two common bean genotypes(new BILFA 58 and Roba 1) varying in soil acidity tolerance.

Study Design: Factorial combinations of five rates of aluminum (0.0, 12.5, 25.0, 50.0, and 100.0 mg Al kg-1 soil) and two genotypes were laid out in a completely randomized design of three replications.

Place and Duration of Study: The experiment was conducted in the vegetation hall of Nekemte Soil Laboratory, western Ethiopia from July to October, 2012.

Methodology: For each treatment, four plants were raised per pot, data related to root growth and aluminum content of the crop were collected at 25 and 35 days after seedling emergence (DAE).

Results: Aluminium and genotype interacted significantly (P=0.01) to affect root growth parameters and aluminium contents of the roots. A difference in inhibition of tap root elongation was observed between the two genotypes at different levels of aluminum. As the applied aluminum level increased, the tap root length of both genotypes decreased under both lime-treated and -untreated soils. On average, application of aluminium led to 14.8, 9.9, 14.6 and 37.3, 22.3 and 16.2%, reduction in root biomass, total root length per volume soil, and root surface area at 25 and 35 DAE, respectively. In contrast lime application resulted in reduction of aluminium content of the roots by 56.3%.

Conclusion: Common bean production on strongly acidic soils with higher contents of exchangeable aluminium could be sustained through the integrated use of tolerant genotypes and application of modest rates of lime.