Early Criterion to Screen Maize Varieties for Their Tolerance to Aluminium Toxic Soil

Tolerance to aluminum toxicity in maize is usually determined after harvesting. This screening process takes place rather too late in the growth stage of the plant and is not economical. In order to speed up the screening of maize va- rieties for their tolerance to aluminum toxicity in Cameroon, a parameter that could be easily detected early in the plant growth stage was investigated. Thirteen (13) maize varieties were evaluated in pots containing aluminum toxic soil and amended soil (less acidic). There were two experimental blocks and the maize varieties were arranged in a completely ran- domized block design with three replications. Young plants were carefully off rooted twenty-one (21) days after planting and soluble phenolic compounds quantified. The results suggested that, phenolic compound production varied with maize variety and the soil type. The amount of phenolic compounds produced on aluminum toxic soil was higher (10.44 x 103µg) than that produced on amended soil with high organic content (6.60 x 103µg) (P< 0.0005). Using LSDs of phenolic compound se- cretion, the 13 varieties were classified into three groups (tolerant, fairly tolerant and sensitive). Ten (10) varieties were tolerant, two were fairly tolerant and one was susceptible. Varieties 91105, 87036, CLA 18, CML 254, CML 247 that were previously unclassified were classified as tolerant to Al toxicity. Variety Exp1 24 that was previously classified as sensitive using using the yield, the interval between anthers and the silk and length of seminal roots was also classified as tolerant using "intact" plants growing under natural conditions confirming that discrepancies may occur when only one method is used for screening. The quantity of phenolic compounds produced in the presence of aluminum could be effectively used to classify maize varieties as tolerant, fairly tolerant and susceptible to soil aluminum toxicity.