In red cultivars like Red Globe, coverage of color on the berries is a critical quality variable. In the province of San Juan, Argentina, environmental conditions favor high concentrations of soluble solids and low concentrations of tartaric acid. Such conditions also prevent good color development on the berries without applications of synthetic growth regulators like ethephon. Currently, countries that import table grapes are demanding reduced use of ethylene, which may constitute a barrier-tariff in the future. This context motivated field trials to evaluate the effect of potassium on color and anthocyanins in berries of Red Globe. The trials were carried out during two seasons. During 2013-2014, the treatments were TA: control; TB: 700 cc 48% ethephon; TC: 700 cc 48% ethephon + 3 kg Color T; TD: 3 kg color T; and TE: 6 kg color T. During 2014-2015, the treatments were: TA: control; TB: 500 cc 48% ethephon; TC: 700 cc 48% ethephon; TD: 500 cc 48% ethephon + 3 kg color T; TE: 500 cc 48% ethephon + 3.6 kg Raisan K; TF: 6 kg color T; and TG: 7.2 kg Raisan K. During both seasons, the treatments were made on clusters with 50% veraison. For TD and TE in season 2013-2014 and TF and TG in 2014-2015, half of the doses were applied at the mentioned time and the rest was applied one week later. The color T product employed consisted of 46% N, 30% K, and 1.5% Mg while Raisan K was 24% N and 2.5% chitosan. The anthocyanin concentration and color of berries in 2013-2014 was greatest in TC clusters, followed by TE. In 2014-2015, the TD and TE treatments had the most anthocyanin and berry color.

Funding Support:  Instituto Nacional de Tecnología Agropecuaria, Argentina (INTA), Fulbright Scholarship, Humphrey Fellows Program