Barley grd5 Dwarf Mutant Accumulates KA. GA-responsive dwarf mutants of Himalaya barley define six different genetic loci (grd1-6) on the basis of complementation grouping (ref. 24 and P.M.C., unpublished data). Analysis of GA biosynthetic intermediates in representatives of the different complementation groups showed that M574, a mutant at the grd5 locus, accumulated KA in developing grains. The GA1 content of M574 grains is only 15% of that of wild-type Himalaya barley (P.M.C., unpublished data). The KA content of developing Himalaya grains remains low (about 1 ng per grain) from 1 to 5 weeks after anthesis, whereas KA accumulates in the grd5 mutant M574, attaining levels of about 60 ng per grain. Grains of Himalaya and M574 were harvested at 2 and 4 weeks after anthesis, and KA, 7OH-KA, and GA12 were measured (Table (Table1).1). The results confirmed the accumulation of KA in developing grains of M574 and demonstrated that there is little if any change in 7OH-KA and GA12. The material identified as KA by GC/multiple ion monitoring showed an excellent match to authentic KA by full-scan GC/MS and GC/multiple-ion monitoring