Growth, Yield and Phytochemical Characterization of Small Watermelon Varieties in Hydroponics

Although the information about hydroponics for growing several vegetable crops is abundant, published data on small watermelon crop are scarce. Considering that the responses of the crop depend on the genotypic characteristics, the aim of this research was to study plant growth, fruit yield, basic composition and content of main phytochemical compounds of four small watermelon hybrid varieties (Extasy Hazeera®, Ki Kodama, Beni Kodama and Tayo Sakama®) grown in the hydroponic NFT system. The obtained results indicated that the varieties presented similar plant dry matter production and partitioning. On average, the fruits comprised 72% of the total dry matter production. The highest fruit yields were attained by ‘Extasy’ and ‘Ki Kodama’ (17.02 and 16.07 kg m-2). The fruits were very similar in pH, total soluble solids and total titratable acidity. In the pulp of variety ‘Ki Kodama’ (yellowish color), the lowest levels of ascorbic acid (AA=48.0 μg g-1), folic acid (FA=0.025 μg g-1), total lycopene (TL =8.0 μg g-1) and total carotenoids (TC=43.0 μg g-1) were detected; besides the lowest antioxidant activity (20.23%). On the other hand, the fruits of ‘Ki Kodama’ presented the highest ß-carotene content (31.0 μg g-1). Varieties of reddish pulp (‘Beni Kodama’, ‘Extasy’ and ‘Taiyo’) did not differ in phytochemicals content, with the following ranges: from 70.7 to 80.0 μg g-1 of AA; from 0.046 to 0.054 μg g-1 of FA; from 56.4 to 65.7 μg g-1 of TL; from 9.7 to 11.0 μg g-1 of ß-carotene and from 70.0 to 80.0 μg g-1 of TC. The results show that varieties present similar plant growth and basic composition of fruits, but ‘Extasy’ and ‘Ki Kodama’ demonstrate larger fruit yield potential. The fruits of the yellow pulp Ki Kodama variety present low levels of phytochemicals, except the high content of ß-carotene, and reduced antioxidant activity. Varieties of reddish color pulp have proper levels of phytochemicals in fruits.