The common bean (Phaseolus vulgaris L.) shows significant sensitivity to low pH levels (4.3), exhibiting considerable genotypic differences in proton sensitivity. Consequently, proton toxicity hampers the screening of common bean genotypes for aluminum (Al) resistance using the established protocol for maize. The experiments were conducted with a set of 28 common bean (Phaseolus vulgaris L.) genotypes like (G685, G855, G3513, G5273, G19227A, G19833, G21212)

Adjusting the pH to 4.5, increasing the Ca2+ concentration to 5 mM, and adding 0.5 mM KCl successfully mitigated proton toxicity in 28 tested genotypes. This allowed for the identification of differences in Al resistance using the inhibition of root elongation by 20 µM Al supply for 36 hours as a parameter of Al injury.

Similar to maize, Al treatment triggered callose formation in the root apices of the common bean. The Al-induced callose formation reflected the effect of Ca supply on Al sensitivity as revealed by root-growth inhibition. Moreover, the Al-induced callose formation in the root apices of 28 bean genotypes, which varied in Al resistance after 36 hours of Al treatment, positively correlated with Al-induced inhibition of root elongation and Al contents in the root apices.

However, the correlation was not as strong as previously reported for maize. Furthermore, after 12 hours of Al treatment, callose formation and Al contents in root apices did not reflect differences in Al resistance between two contrasting genotypes. This suggests a different mode of expression of Al toxicity and regulation of Al resistance in common beans compared to maize.