371 Enhancing Anthocyanin Production and Maturity Uniformity of Apples Without Over-ripening

Abstract

Multiple harvests are often necessary to achieve maximum yield of well-colored high-quality apples. This is true for most cultivars, and particularly for `Gala'. Multiple harvests add significantly to the cost of producing apples. We tested our hypotheses that anthocyanin production of ReTain™-treated apples may be enhanced by ethephon without overly stimulating other ripening processes and ReTain™ may promote uniform maturation of apples within and between trees by delaying maturation and ripening processes. Experiments were conducted with `Gala', `Empire', and `Jonagold' apples at the MSU CHES in 1997 and 1998 employing the rootstock/training systems research plot. Treatments were 1) ReTain™ (50g/ac.) applied 3 to 4 weeks before harvest, 2) ReTain™ followed by ethephon (3/4 pt/ac.) applied 1 to 2 weeks before harvest, 3) ethephon, and 4) control (Silwet® L-77 surfactant only). ReTain™ applied alone delayed the onset of the ethylene climacteric and red color development of `Gala' apples. ReTain™ followed by ethephon delayed the onset of the ethylene climacteric and red color development at the commercial harvest date was not significantly affected. Similar results were obtained with the `Empire' and `Jonagold'. Results with ReTain™ and ReTain™ + ethephon in 1998 on `Gala', `Empire', and `Jonagold' apples were more profound than in 1997; we attribute this to less environmental stress on the trees, which were well-irrigated in 1998. The ripening-related effects of treatments were reflected in the storability of fruit 1997 in air and particularly during CA storage where the action of ethylene in ripening can be attenuated. ReTain™ - and ReTain™ + ethephon-treated fruit were still at preclimacteric ethylene levels after 6 months in CA with excellent retention of flesh firmness and shelf-life, while ethephon and control fruit had higher ethylene levels and softened more during storage and shelf-life evaluation.