Carbohydrate Levels and the Development of Fruit in Cranberry

Abstract

Cranberry (Vaccinium macrocarpon Ait. cv. Searles) vegetative tissue was analyzed at various stages of development to determine carbohydrate levels under field and greenhouse conditions and to identify the carbohydrates. Except during dormancy, cranberry uprights in the field had the highest concentration of carbohydrates (soluble and starch) at early blossom, when the lower flowers were at anthesis. As early flowers developed into fruit and upper flowers were at or just beyond anthesis, uprights had lower carbohydrate concentrations. As fruit growth slowed, soluble carbohydrate levels increased and were highest at dormancy. Upright shoot tissue produced the previous year and trailing woody stems followed the same trend as the current season's growth but had consistently lower soluble carbohydrate levels at each growth stage. Starch levels were low in current growth and did not change appreciably with fruit development. Starch was primarily stored and subsequently depleted in the previous season's upright growth and trailing woody stems. Tissue from the greenhouse was generally higher in carbohydrates than was field-grown tissue. Fruit developed from 53% of the flowers under greenhouse conditions, compared to 38% in the field. Insufficient carbohydrate levels may be responsible for the low fruit set observed in the field. Sucrose, glucose, fructose, raffinose, and stachyose were present in cranberry vegetative tissue.