Genetic and physiological evidence for the role of gibberellic acid in the germination of dormant Avena fatua seeds

Genetic and physiological data indicate that gibberellic acid does not have a primary role in the regulation of seed dormancy in wild oat (Avena fatua L.). The gibberellic acid sensitivity threshold of dormant caryopses imbibed for 7 d was 1 µM. Intact dormant seeds were after-ripened for 0, 2, 4, 8, 12, 16, and 20 weeks at 40 °C and imbibed in H2O, 100 nM or 1 µM gibberellic acid. The length of the after-ripening interval was inversely related to the mean base gibberellic acid concentration (the concentration resulting in 50% germination). Thus, after-ripening, not gibberellic acid, is the principal factor that regulates the release of seed dormancy in wild oat. F2 caryopses (dormant×non-dormant) classified by germination response to progressively higher gibberellic acid concentrations, were pooled according to their gibberellic acid requirement: low, medium and high. Germination responses of the F3 progeny from the low, medium, and high gibberellic acid requirement pools were regressed on to the F2 parent values, and a heritability for germination response to gibberellic acid, h2=0.24, was calculated. Random amplified polymorphic DNA analysis of DNA samples from F2 pools requiring low and high gibberellic acid concentrations were screened with 200 decamer primers and no polymorphisms were found. The findings of this investigation demonstrate that gibberellic acid is not the primary regulator of seed dormancy in wild oat.