RFLP MAPPING OF QUANTITATIVE TRAIT LOCI CONTROLLING ABSCISIC-ACID CONCENTRATION IN LEAVES OF DROUGHT-STRESSED MAIZE (ZEA-MAYS L.)

Abscisic acid (ABA) concentration in leaves of drought-stressed plants is a quantitatively inherited trait. In order to identify quantitativ e trait loci (QTLs) controlling leaf ABA concentration (L-ABA) in maiz e, leaf samples were collected from 80 F-3:4 families of the cross Os4 20 (high L-ABA) x IAB078 (low L-ABA) tested under drought conditions i n field trials conducted over 2 years. In each year, leaf samples were collected at stem elongation and near anthesis. The genetic map obtai ned with 106 restriction fragment length polymorphism (RFLP) loci cove red 1370 cM, which represented approximately 85% of the UMC maize map. Sixteen different QTLs with a LOD > 2.0 were revealed in at least one sampling. Across samplings, only four QTLs significantly influenced L -ABA, accounting for 66% of the phenotypic variation and 76% of the ge netic variation among families. At these QTLs, the alleles which incre ased L-ABA were contributed by Os420. The two most important QTLs were mapped on chromosome 2 near csu133 and csu109a. The effects associate d with the QTL near csu133 were more pronounced near anthesis. The sup port intervals of the four primary QTLs for L-ABA did not overlap the presumed map position of mutants impaired in ABA biosynthesis.