Inhibition of Apple Ripening by Succinic Acid, 2,2-Dimethyl Hydrazide and its Reversal by Ethylene

Ripening of McIntosh apples (Malus sylvestris L.) was delayed by treatments of succinic acid 2,2-dimethyl hydrazide (B-9) applied 2 weeks after bloom. The extent of retardation was dependent on concentration to 7.4 x 10(-2)m, at which level complete inhibition of ripening occurred under the conditions applied. The onset of the respiratory climacteric and fruit firmness changes were factors used to assess ripening.The inhibitory effect of B-9 was counteracted by 100 ppm of ethylene. This counteraction was independent of B-9 concentration or chronological age of fruit during the period of July 4 to September 20, 1967. The data suggest that B-9 suppresses ethylene biosynthesis or action within the fruit and that this suppression is not related to fruit maturity.