臺灣荔枝品種及其改良

The Cultivars of Litchi (Litchi chinensis Sonn.) and Their Improvement in Taiwan

荔枝育種計劃始於民國71年，主要工作為種源蒐集，自然授粉實生選種及人工雜交育種，育種目標為不同產期、豐產、適應性、優良品質及風味、大果及高小率等。初步自本省調查獲20已命名品種及21變異品系，並選出4個具有早熟、豐產及高小核率之優良品系。依果實性狀可將本省荔枝品種分成三大系統。荔枝開花及授粉方式於本文中另加討論，為增加自然雜交授粉比率，設立多品種雜交基因庫，包括14主要品種。於前2年自本省各地自然授粉果園獲得約2500株實生苗已密植田間供選種。人工雜交授粉以港尾，淮荔，沙坑及黑葉等品種之著果率較高，較適宜為授粉母本。為提高育種效率，已採行密植及縮短幼年期等方法，於本文中詳加討論。

The litchi (Litchi chinensis, Sonn,) breeding program mainly including germplasm. collection and selection of seedlings from open-and controlled-pollioation was started in Taiwan in 1982. Twenty cultivars and 21 selections collected locally ware evaluated. The cultivars capable of providing superior gene sources were discussed. Four promising selections of high yielding, high quality, earliness and with high percentage of small-seeded fruits will be further evaluated. The breeding goals are listed as follows according to priority (in parentheses are the varieties that may provide the gene sources): 1. Various mature seasons to extend the supply of litchi in Taiwan (very early-Sun Yueh Hong, very late-Hwai Li). 2. High yielding and wide adaptability (Hak IP). 3. High quality and sweet fragrance (Yu Her Pan and No Mai Tsz). 4. Large fruit size (Yu Her Pau, Sun Yueh Hong and Sah Keng). 5. High percentage of small-seeded fruits (No Mei Tsz, Yu Her Pau and Sah Keng). 6. Fruit with bright and colorful red skin and smooth protuberances (No Mai Tsz and Kwsi Mi). 7. Vigorous (Yu Her Pau). 8. Processing for dried litchi nut (No Mai Tsz). 9. Long storage life. 10. Resistant to pests and diseases (downy blight, fruit borer and longicorn beetle) as well as low percentage of skin-cracking fruits. According to fruit characters, the collections of litchi were divided into three distinct group: Group Ⅰ (or Hon Li Group): Usually early and mature during early June in Chic Yi ares. Fruit oblong to ovoid, bright red, with distict protuberances, and generally large seeded. Fruit weighs between 20 to 25 grams. This group includes Kau Shiung Early, Vu Her Pau, Hon Pi, Foo Chow, Wan Nien Hong and Chung Yuan Hong. Group Ⅱ (or Hak Ip Group): Mature during middle and late June in Chic Yi. Fruit cordate and dark red; protuberances usually turn smooth toward maturity. Fruit weighs about 20 grams. This group includes Hak Ip, Kwang Tung, Rang Wei Late, Sah Keng sad Sun Yueh Hong. Group Ⅲ (or Kwai Mi Group): Generally late and mature during early July in Chia Yi. Fruit nearly globular and colorfully red; rough protuberances usually turn smooth toward maturity. Fruit weighs between 17 to 22 grams. Generally a specific fragrance could be tasted in aril in most varieties of this group and its content varied with different varieties. The acid content of fruit decrease rapidly and is eatable when the skin just turns light red. This group includes Kwai Mi, No Mai Tsz, Hwai Li, Hwai Chih, Kwai Chih, Shang Shu Hwai, Tang Po and Hsin Hsin. The flowering behavior and pollination techniques were discussed, and both open-and controlled-pollination were followed in litchi breeding program. An multi-varieties gene pool orchard composed of 14 varieties with 9 replications was established to increase the hybridization ratio under natural condition. In the first 2 years, totaling about 2500 seedlings were collected from open-pollinated orchard and planted for future selection. Controlled-pollination was also conducted to combine superior characters as well as to overcome the difference in flowering time between early and late varieties that could not be hybridized under natural condition. From fruit-sets obtained in controlled hybridization indicated that Kang Wei, Hwai Li, Sah Keng and Hak Ip could set more fruits and were more suitable as mother plant than other varieties in controlled- pollination. The methods to increase the efficiency of breeding litchi were tested. Handling the seedling with high population density was practiced to reduce the cost and save the land use. Top-working and the possibility of chemical sprays to shorten the juvenile phase were discussed.