Use of External Indicators to Predict Maturity of Mini-watermelon Fruit

Abstract

Mini-watermelon [Citrullus lanatus (Thunb.)] cultivars Valdoria and Vanessa were evaluated at 20, 30, 40, or 50 days after anthesis to determine maturity at harvest. Fruit circumference, weight, ground spot color, and number of senescent tendrils were measured as external indicators for each watermelon. Soluble solids content (SS), pH, and SS:total acid ratio (SS:TA) of each watermelon were determined to provide an indication of internal maturity. Regression and Akaike Information Criterion fit statistics analyses were performed to determine significant relationships and best predictors for external indicators of internal maturity factors. In this study, external predictors were most closely linked to fruit pH rather than to SS or SS/TA. Of the external indicators tested, fruit weight, circumference, number of senescent tendrils, and International Commission on Illumination (CIE) b* color coordinate values of the ground spot were best related to fruit pH. According to the regression models, two completely senesced tendrils, a circumference of 53 cm, weight of 3 kg, and CIE b* coordinate ground spot value of 40 are each sufficient to predict maturity when pH is used as the internal indicator of maturity under the conditions of this experiment.