Research activities of this Department center around the improvement of varieties and cultivation techniques of tropical fruit trees. Through the efforts of introduction, selection and cross breeding, the Department has released many varieties of fruits. Papaya varieties include Tainung No. 1, 2, 3 and 6 (Chu-Yu), and ring spot virus tolerant Tainung No. 5. For mango, two varieties with unique fruit aroma and shape have been developed, i.e., Tainung No. 1 and 2, which, along with the introduced varieties Irwin, Haden, Sensation and Keitt, offer diverse consumer choice and prolong the availability of mango fruits. Lychee varieties include Tainung No. 2 (Wuang Lee), Tainung No. 4 (Lucky) and Tainung No. 5 (Colorful); they are suited to different locations in Taiwan, prolonging the availability of lychee fruits, and increasing farmers' profits. Pineapple varieties include fresh market type Tainung No. 11 (Perfumed Pineapple), which has a distinct aroma, and Tainung No. 20 (Milky Pineapple), which is characterized by its delicate and low fiber flesh. Passion fruit Tainung No. 1 features a self-compatibility rate over 60%, and has become a major variety in Taiwan. Carambola Tainung No. 1, 2 (Jheng Gang), 3 (Red Dragon) and 4 (Golden Dragon) have brought increased export opportunities. Indian jujube varieties include large-fruited Tainung No. 1, 4 (Blue Dragon) and 9 (New Honey King). The superior guava variety, Tainung No. 1 (King), is distinguished by the flesh quality, which is not so easy to soften when ripe. Tainung No. 1 (Amethyst) is the first wax apple variety developed by Taiwan through cross breeding. The aforementioned varieties have been well accepted by farmers and consumers. In addition, the Department is devoting to the improvement of dragon fruit and other new fruit trees.