NORMAL RIPENING CULTIVARS OF PYRUS-SEROTINA ARE EITHER CLIMACTERIC OR NONCLIMACTERIC

The climacteric status has been investigated in two cultivars of Pyrus serotina (Rehder). Both cultivars are chance seedlings. The fruit displayed a high respiration rate early in development that declined as fruit matured. Both ripened, as seen by skin degreening and softening, at similar times after flowering. Yet only in cultivar 'Chojuro' were the ripening changes associated with increased rates of ethylene and carbon dioxide production. In cultivar 'Nijisseiki' ethylene and carbon dioxide did not increase as fruit ripened. Continuous exposure of fruit to propylene accelerated skin degreening in cultivar 'Nijisseiki' but did not induce ethylene production or a climacteric peak of respiration. Whereas, in 'Chojuro', skin degreening, and ethylene and carbon dioxide production were all advanced after exposure to propylene. We conclude that although fruit development and ripening of both cultivars are similar, 'Chojuro' ripens with an associated respiratory climacteric, whereas 'Nijisseiki' does not.