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United States Department of Agriculture

Agricultural Research Service

Research Project: Optimizing Foliar Potassium Use in Table Grape Vineyards

Location: Commodity Protection and Quality

2012 Annual Report


1a.Objectives (from AD-416):
The primarily objective is to examine the interaction of vineyard treatments of foliar potassium, ethephon, abscisic acid and irrigation regimens on color development and quality of table grapes.


1b.Approach (from AD-416):
Three factorial split plot vineyard experiments examining the effect of plant growth regulator interactions with foliar potassium applications are proposed: ‘Flame Seedless’ in two experiments (Coachella Valley and San Joaquin Valley) and ‘Crimson Seedless’ in one experiment (San Joaquin Valley). The incidence of summer bunch rot disease and postharvest decay will be recorded, as will the quality of the fruit will be documented before harvest, the day of harvest, and after long storage.


3.Progress Report:

Progress in FY 2012 was made on an objective of NP306, Problem Area 1b. Methods to Evaluate and Predict Quality, Objective: Determine influence of pre-harvest factors on quality, including genetics, production practices and environment. In a prior project, late season application of potassium compounds improved the quality and prolonged storage life of fresh grapes. But the interactions of this practice with two commonly used growth regulators (ethephon and abscisic acid) and deficit irrigation were not known. A ‘Flame Seedless’ vineyard in Indio, California and a Crimson Seedless vineyard in Exeter, California were selected and potassium, ethephon, abscisic acid, and a deficit irrigation were applied in various regimes to developing grape clusters to determine their impact on berry quality. Berry quality is defined by determinations of fruit color, size, firmness, contents of sugar, acid, and potassium, and incidence of decay pathogens at harvest and during storage. Preliminary results with ‘Flame Seedless’ indicate ethephon and potassium applications interact positively and markedly increased berry color and sugar content.


Last Modified: 8/21/2014
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