Deficit irrigation influences yield and lycopene content of diploid and triploid watermelon

Many vegetable production regions in the southwestern US are strictly regulated on water use. In addition, demand for high quality and nutritious vegetables has increased. This study was performed to explore the effects of deficit irrigation on yield, fruit quality and lycopene content of red-fleshed diploid and triploid watermelon (Citrullus lanatus (Thunb) Matsum & Nakai) cultivars. Irrigation treatments were 1.0, 0.75 and 0.5 evapotranspiration (ET) rates. Cultivars used were ‘Summer Flavor 710’, ‘RWW 8036’, ‘Allsweet’, ‘Sugarlee’, and ‘SWD 7302’ (diploids) and ‘Summer Sweet 5244’, ‘SWT 8706’, ‘Sugar Time’, and ‘Tri-XSunrise’ (triploids). Total water applied through a subsurface drip system was 395, 298 and 173 mm, for the 1.0, 0.75 and 0.50 ET, respectively. Total yields were highest at 1.0 ET (53.9 t ha-1) compared with 0.5 ET (26.8 t ha-1). Triploids had a 34% higher total yield and fewer culls (2%) compared with diploid cultivars (25%). Highest yields were obtained for ‘Sunrise’, ‘SWT 8706’, and ‘SWD 7302’. Highest soluble solid content was measured for ‘Sugar Time’ (13.4%) and was significantly higher than other cultivars (range 9.7-11.0 %). Triploid cultivars had more firm flesh, compared with diploids (12.0 vs. 9.9 N). Lycopene content increased slightly with maturity (55.8 to 60.2 :g g-1 fw), and was significantly higher at 0.75 ET than 1.0 ET in melons at ripe and overripe maturity stages. Lycopene content averaged over all treatments was 60-66 :g g-1 fw for triploids and 45 to 80 μg g-1 fw for diploid fruit.The authors thank the Texas Department of Agriculture and USDA for their partial financial support, to Sakata, Novartis, Abbott & Cobb, Willwhite, and Sugar Creek Seeds for providing seeds, and to Tropical Star for growing the transplants

Variation in Key Flavonoid Biosynthetic Enzymes and Phytochemicals in ‘Rio Red’ Grapefruit (Citrus paradisi Macf.) during Fruit Development

In the current study, the phytochemical contents and expression of genes involved in flavonoid biosynthesis in Rio Red grapefruit were studied at different developmental and maturity stages for the first time. Grapefruit were harvested in June, August, November, January, and April and analyzed for the levels of carotenoids, vitamin C, limonoids, flavonoids, and furocoumarins by HPLC. In addition, genes encoding for phenylalanine ammonia-lyase (<i>PAL</i>), chalcone synthase (<i>CHS</i>), chalcone isomerase (<i>CHI</i>), and 1,2-rhamnosyltransferase (<i>2RT</i>) were isolated, and their expression in grapefruit juice vesicles was studied. Fruit maturity had significant influence on the expression of the genes, with <i>PAL</i>, <i>CHS</i>, and <i>CHI</i> having higher expression in immature fruits (June), whereas <i>2RT</i> expression was higher in mature fruits (November and January). The levels of flavonoids (except naringin and poncirin), vitamin C, and furocoumarins gradually decreased from June to April. Furthermore, limonin levels sharply decreased in January. Lycopene decreased whereas β-carotene gradually increased with fruit maturity. Naringin did not exactly follow the pattern of <i>2RT</i> or of <i>PAL</i>, <i>CHS</i>, and <i>CHI</i> expression, indicating that the four genes may have complementary effects on the level of naringin. Nevertheless, of the marketable fruit stages, early-season grapefruits harvested in November contained more beneficial phytochemicals as compared to mid- and late-season fruits harvested in January and April, respectively