Isolation and characterization of abscisic acid‐deficient Arabidopsis mutants at two new loci

Novel Arabidopsis mutants with lowered levels of endogenous abscisic acid (ABA) were isolated. These were selected in a screen for germination in the presence of the gibberellin biosynthesis inhibitor paclobutrazol. Another mutant was isolated in a screen for NaCl tolerance. The ABA‐deficiency was caused by two monogenic, recessive mutations, aba2 and aba3 , that were both located on chromosome 1. The mutants showed a phenotype that is known to be characteristic for ABA‐deficiency: a reduced seed dormancy and excessive water loss, leading to a wilty phenotype. Double mutant analysis, combining different aba mutations, indicated the leaky nature of the mutations.