LOCATION OF A GENE REGULATING DROUGHT-INDUCED ABSCISIC-ACID PRODUCTION ON THE LONG ARM OF CHROMOSOME 5A OF WHEAT

The accumulation of abscisic acid (ABA) by detached and partially dehy drated wheat leaves is known to be inherited in a quantitative manner. The location of genes having a major effect on drought-induced ABA ac cumulation in wheat was determined using a set of single chromosome su bstitution lines and populations derived from a cross between a high-A BA- and a low-ABA-producing genotype. Examination of a series of chrom osome substitution lines of the high-ABA genotype 'Ciano 67' into the low-ABA recipient 'Chinese Spring' showed that chromosome 5A carries g ene(s) that have a major influence on ABA accumulation in a drought te st with detached and partially dehydrated leaves (DLT). A similar DLT was used to examine ABA accumulation in a population of F-2 plants and doubled haploid (DH) lines derived from the cross between 'Chinese Sp ring' (low-ABA) and 'SQ1' (high-ABA) in which the F-2 population (139 plants) and DH lines (96 lines) were also mapped partially with molecu lar markers. Analysis of variance of ABA accumulation between and with in marker allele classes in the F-2 confirmed the location of a gene(s ) regulating ABA accumulation on the long arm of chromosome 5A. MAPMAK ER-QTL showed the most likely position for the ABA quantitative trait locus (QTL) to be between the loci Xpsr575 and Xpsr426, about 8 cM fro m Xpsr426. A similar trend for high ABA accumulation was found in DH l ines having the 'SQ1' allele at marker loci in the same region of chro mosome 5AL, but the QTL effect was not significant. The function of th e QTL is discussed.