Eight experiments were carried out in nutrient solutions under greenhouse conditions at the Instituto Agronômico Experimental Center, located at Campinas, State of São Paulo, Brazil. The main objective of this study was to determine the relationship between P-use efficiency and Al-tolerance of 50 lowland rice cultivars, 50 upland rice cultivars, and 40 maize inbred lines. Using the 99.9% confidence interval for the mean values of P-efficiency and Al-tolerance, respectively for each crop group, the genotypes were classified in nine classes: I. Efficient to P and tolerant to Al (ET); II. Efficient to P and intermediate to Al (El); III. Efficient to Pand non-tolerant to Al (ENT); IV. Intermediate to P and tolerant to Al (IT); V. Intermediate to P and intermediate to Al (II); VI. Intermediate to P and non-tolerant to Al (INT); VII. Non-efficient to P and tolerant to Al (NET); VIII. Non-efficient to P and intermediate to Al (NEI); and, IX Non-efficient to P and non-tolerant to Al (NENT). The non-efficient or non-tolerant, the intermediate, and the efficient or tolerant are those classes whose values are lesser, equal or greater than the confidence interval, respectively. In rice, the upland cultivars were more tolerant to Al but less efficient to P than the lowland cultivars. Ten upland and five lowland rice cultivars could be classified as efficient to P and tolerant to Al (ET). In maize, an inverse relationship was found between efficiency to P and tolerance to Al. Three inbred lines could be classified as intermediate to P and tolerant to Al (IT). For the genetic material used in this study, it was found a poor correlation between the two plant traits indicating that they are independent.
rice; corn; P-efficiency; Al-tolerance