We studied the genetics of Al toxicity tolerance using a full diallel set of crosses among seven parents with differing degrees of response to Al toxicity. The seven varieties were Moroberekan, IRAT104, and Azucena (tolerant); IR29 and IR43 (moderately tolerant); and IR45 and IR1552 (susceptible).
Relative root length of 14-d-old seedlings, determined by growing seedlings in a normal nutrient solution and nutrient solution with 30 ppm Al, was used to characterize the tolerance of test materials. The experiment was conducted in a glasshouse at the IRRI Phytotron with 29/21 ºC day/night temperature and 70% relative humidity. The experimental units consisted of 49 entries (7 × 7 diallel) in randomized complete block design with four replications. Eight seedlings were sampled for each entry in a replication.