Dwarf (di)haploid pito mutants obtained from a tetraploid potato cultivar (Solanum tuberosum subsp tuberosum) via anther culture are defective in gibberellin biosynthesis

Nine dwarf (di)haploid lines (2n = 2 x = 24) were obtained from the tetraploid (2n = 4 x = 48), long day-adapted potato cultivar 'Pito'- (Solanum tuberosum subsp. tuberosum) through anther culture. They grew slowly, had very short internodes, compact and ball-shaped appearance, and dark green leaves. Dwarfism was due to a recessive gene, designated pito. Endogenous gibberellin contents were measured in the leaves of dwarf and wild-type lines by gas chromatography linked to mass spectrometry (GC-MS). High amounts of GA(19), GA(20), GA(29), GA(1), and GA(8) were detected in the wild-type plants, which indicated that the early 13-hydroxylation pathway was predominantly used for GA biosynthesis in S. t. subsp. tuberosum. Also GA(53), GA(15) and GA(9) were detected but not quantified. Very low endogenous amounts of all analysed GAs Were detected in the pito mutants, indicating a block at an early part of the GA biosynthesis pathway. The dwarf lines strongly and quickly responded to the exogenous application of low amounts (79 nM) of bioactive GA (GA(3)), which restored normal growth and confirmed that the pito dwarfs were synthesis mutants and not GA response mutants. 1999 Elsevier Science Ireland Ltd. All rights reserved.