Title:
Location of a gene regulating drought-induced abscisic acid production on the long arm of chromosome 5A of wheat.

Abstract:
The accumulation of abscisic acid (ABA) by detached and partially dehydrated wheat leaves is known to be inherited in a quantitative manner. The location of genes having a major effect on drought-induced ABA accumulation in wheat was determined using a set of single chromosome substitution lines and populations derived from a cross between a high-ABA- and a low-ABA-producing genotype. Examination of a series of chromosome substitution lines of the high-ABA genotype 'Ciano 67' into the low-ABA recipient 'Chinese Spring' showed that chromosome 5A carries gene(s) that have a major influence on ABA accumulation in a drought test with detached and partially dehydrated leaves (DLT). A similar DLT was used to examine ABA accumulation in a population of F2 plants and doubled haploid (DH) lines derived from the cross between 'Chinese Spring' (low-ABA) and 'SQ1' (high-ABA) in which the F2 population (139 plants) and DH lines (96 lines) were also mapped partially with molecular markers. Analysis of variance of ABA accumulation between and within marker allele classes in the F2 confirmed the location of a gene(s) regulating ABA accumulation on the long arm of chromosome 5A. MAPMAKERQTL showed the most likely position for the ABA quantitative trait locus (QTL) to be between the loci Xpsr575 and Xpsr426, about 8 cM from Xpsr426. A similar trend for high ABA accumulation was found in DH lines having the 'SQ1' allele at marker loci in the same region of chromosome 5AL, but the QTL effect was not significant. The function of the QTL is discussed.