MAPPING QUANTITATIVE TRAIT LOCI FOR TOLERANCE TO ABIOTIC STRESSES IN MAIZE

Water deficits and high temperature are major abiotic stresses affecti ng crop productivity. In order to unravel the genetic architecture of maize tolerance to these stresses, linkage analysis between the expres sion of the two tolerance traits and allelic composition of molecular markers was performed. The study was carried out on two separate panel s of recombinant inbred Lines (RILs). The first, T x CM, consists of 4 8 RILs for which a densely saturated molecular marker map was already available and was used for thermotolerance analysis; the second panel, B73 x H99, 142 RILs, was characterized by 50 RFLPs and 70 microsatell ites and was used for water stress tolerance evaluation. Different com ponents for the two tolerance traits were analyzed, and for each of th em several quantitative trait loci (QTLs) were detected. With the aim of identifying ''major QTLs,'' potential candidates for marker-assiste d selection, the map positions of the QTLs detected for the different components and in the two panels were compared. The analysis revealed four genomic regions, on chromosomes 2, 4, and 6, containing factors c ontrolling cell membrane stability, a major tolerance component, under both high temperature and water stress. Furthermore, a preliminary an alysis indicated that some rab genes, known to be induced by drought a nd abscissic acid, roughly map to the same regions as QTLs for water s tress tolerance. These data are discussed in relation to a possible ro le of these genes in providing tolerance to water deficits. J. Exp. Zo ol. 282:164-170, 1998. (C) 1998 Wiley-Liss, Inc.