An agar plate method for rapid screening of Rhizobium for tolerance to aluminum

An agar plate method has been developed for the rapid, preliminary screening of large numbers of rhizohia for tolerance to acidity and aluminum (acid-Al). Media containing pH indicators are used, and distinguish true tolerance from cases where growth depends on a previous pH shift. Strains which were highly tolerant or sensitive to acid Al on agar behaved similarly in defined liquid media. Strains that formed dry, pinpoint colonies were more sensitive to acid-Al than those that formed large, gummy colonies.