Aluminum-tolerance QTL in Columbia/Kashmir inbred population of Arabidopsis thaliana is not associated with aluminum-responsive malate excretion

Aluminum (At) tolerance is one of the most important target traits for improving crop production in acid soil. To understand the complex molecular mechanism of At tolerance, QTL analysis in Arabidopsis would be one useful approach. Using relative root length as the Al-tolerance index, both composite interval mapping and complete pair-wise searches were performed to identify major QTL and epistatic interacting loci pairs, in the Columbia (Col)/Kashmir (Kas) recombinant inbred population. At tolerance among ecotypes was highly correlated with Al-responsive malate release and a major QTL detected for the RI populations derived from Al-tolerant and -sensitive ecotypes was associated with this function. However, these traits of both Col and Kas were similar and no relationship was found between Al-tolerance and -responsive malate release among the Col/Kas recombinant inbred population. In this case, QTLs detected from Col/Kas population overlapped the chromosomal position of a previously identified major QTL that did not associate with Al-responsive malate release. Two out of five detected epistatic interacting loci pairs were also closely related to chromosomal positions of epistasis identified in previous studies. These chromosomal regions, which were identified as pyramided QTL and epistatic, contain important genes for At tolerance, but not associated with At-responsive malate release. (c) 2008 Elsevier Ireland Ltd. All rights reserved.