Influence of different potassium fertilization regimes on quality aspects and yield of cocktail tomato cultivars

Abstract

The tomato (Solanum lycopersicum L.) is a worldwide important vegetable, with an annual production of 170.8 million tons in 2014. Potassium (K) has several physiological functions in plants, such as translocation of assimilates, activation of enzymes, maintenance of turgescence, and stomata regulation and thereby contributes to fruit yield and quality. The aim of all experiments was to investigate the impact of increasing K application on tomato fruit quality for a better understanding of K’s physiological functions. Therefore, different cocktail tomato cultivars (Primavera, Resi, and Yellow Submarine) were studied in two consecutive years in outdoor pot experiments. Total soluble solids (TSS), titratable acids (TA), dry matter (DM), color, and firmness are important consumer-related quality traits. Especially high concentration of TSS and TA are taste beneficial. In all studied cultivars TSS, TA, and partly DM increased with rising K fertilization. Other parameters, such as color, firmness and yield increased in Primavera in both years, whereas in Resi no further changes were detected. This clear cultivar dependence shows that high K fertilization not necessary enhance these traits. Tomatoes contain several important water- and fat-soluble antioxidants, like ascorbic acid, phenolics, carotenoids, and tocopherols. The antioxidant concentrations in tomato fruit are affected by K fertilization, but other abiotic factors may alter or even reverse those effects in an outdoor environment. Nevertheless, the tendencies of ascorbic acid, naringenin, pcoumaric acid, and caffeic acid are similar in both years for Primavera and Resi, indicating a strong K fertilization effect. The metabolome analysis provides a comprehensive overview of the induced changes by increasing K fertilization on low weight metabolites in tomato fruits. The cultivarindependent increase of TCA cycle metabolites and decrease of amines with rising K fertilization was most prominent. Several other metabolites showed a cultivar-specific effect. Indicating that the reaction towards macronutrient stress is quite different between cultivars of one species.