In recent 40 years, the research of longan in China has developed, and the investigation and arrangement of longan variety resources and the identification and evaluation of main fruit characters have been completed in most producing areas, and the main cultivated varieties and rare and excellent varieties have been put forward in various places. China is rich in longan variety resources. According to incomplete statistics, there are about 300 varieties and strains in China, with Fujian and Guangdong provinces as the largest. On the basis of resource investigation, the Ministry of Agriculture established the Fujian National Fruit Tree Germplasm (Fuzhou) Longan Variety Resource Garden on 1985, collected and preserved 202 varieties and strains, and made identification and evaluation. The scientific research and teaching departments in Guangdong and Yunnan have successively investigated and found wild longan communities and wild longan mixed forests in Wuzhishan, Hainan and southwest Yunnan. At the same time, seed selection was carried out, and a number of excellent plants with early maturity, late maturity, high quality and scorched core were obtained. In the aspect of seedling raising technology, grafting seedling raising technology has been popularized in the production area through experiments, which has gradually replaced the long-term seedling raising mode and effectively promoted the popularization and popularization of improved varieties. The biological characteristics, morphological anatomy, palynology, flower bud differentiation, leaf nutrition diagnosis, element deficiency disease, tissue culture, pathogen (virus disease) and virus vector of longan witches' broom disease were studied, which provided the basis for high yield and high quality cultivation. At the same time, some progress has been made in overcoming age, rejuvenating old trees, storing fresh fruits at low temperature, and applying potassium chlorate to promote flowers in soil. Especially in recent 20 years, some breakthroughs have been made in the research of longan genetics, somatic genetics and molecular biology in China, which will provide a good foundation for the development of longan genetics and variety improvement in China.
The rapid development of longan production in China has not only promoted the comprehensive development of hilly areas in southern China, but also made great contributions to increasing agricultural efficiency and farmers' income. However, in the 1990s, with the rapid development of the national fruit industry and the fluctuation of fruit market regulation, fruit farmers who thought longan was "not worried about selling, getting rich and making money" encountered unexpected challenges. Especially since 1995, due to the substantial increase of longan planting area and fruit yield in China, a series of problems, from poor sales to difficulty in selling fruits, have quietly struck, which has made fruit farmers lose confidence in operating longan, and the wave of declining benefits has posed a certain threat to the development of longan in China, and there have been rough management and out-of-stock phenomena in various places. At present, the supply of longan exceeds demand, which is only caused by a large number of outdated varieties, unreasonable structure, few fresh varieties, small export volume (only accounting for 5.3% of the total output of longan), poor quality of fruits entering the market, unsalable sales contrary to market demand, large circulation taxes and fees, and weak market consumption demand. To make longan develop continuously in China, we must rely on scientific and technological progress. In the future, as long as we renew our ideas, continue to give full play to the advantages of ecological environment in the best planting area and certain product quantity and scale operation, increase investment in science and technology and property, strive to improve the output, quality and commodity rate, effectively reduce the production cost, and participate in the competition with large quantity, high quality and low price, we can firmly believe that China longan will continue to occupy the domestic market, expand its exports, and maintain high economic benefits, thus creating greater glory for the development of rural economy in China.
It is a very complicated system engineering to realize the sustainable development of longan in China. But the most fundamental thing is to closely combine the progress of science and technology with the development of fruit industry and transform new scientific and technological achievements into real productive forces. At present, the problems that need to be solved for the sustainable development of longan in China are:
(1) has a single variety and lacks high-quality fresh varieties. Longan planting in China has a long history and rich resources. Historically, a considerable number of longan producing areas in China have been using seedling propagation, so the varieties are mixed. But after long-term natural and artificial selection and domestication, many varieties have also been formed. According to incomplete statistics, there are nearly 300 varieties in China, most of which are in Fujian and Guangdong provinces, and there are also many longan varieties with excellent economic properties, such as Wulongling and Youmandarin, which are famous for baking Xinghua longan at home and abroad, Yanfu and Shuizhang, which are canned in sugar water, Dongbi and Chulianglongyan, which are fresh, and Shijie and crispy meat, which are deeply loved by overseas Chinese in Hong Kong and Macao. As a result, longan varieties in the main producing areas in China are relatively single, and there are few excellent varieties with early maturity and late maturity. For example, among the 28,000 hectares of longan trees in Quanzhou, Fujian, Yanfu alone accounts for 94%, and most of them are supplied to the market in early September, which brings difficulties to harvesting, sales and processing, and is not conducive to extending the market supply period. Especially with the popularization of fresh fruit in today's fruit market, most varieties cultivated in China do not have the excellent freshness of fruit comprehensive economic properties such as large fruit (14g or more), sweet taste (soluble solids 18% or more), high edible rate (70% or more) and crisp meat, so they are not competitive in the international fresh fruit market. In recent years, China has also cultivated a number of excellent fresh food varieties with strong international competitiveness, such as Chuliang Longyan in Gaozhou, Guangdong, Gudian No.2 in Xianyou, Fujian, Longan 1 in Shuinan, Putian, Bayi Zao Longan in Tongan and Qingke Baoyuan in Changle. However, due to the long-term influence of small farmers and planned economy, the concept of commodity market is weak, and the longevity of longan trees is long, and the tissue culture and rapid propagation technology has not yet broken through, so the promotion of these excellent varieties is slow. Therefore, it has become an important task to strengthen the breeding of new varieties and the promotion of excellent varieties to develop longan production in China.
Longan is an ecotype fruit tree in China, which requires strict climatic conditions. Therefore, it is limited to the expansion of cultivation and the geographical distribution is very narrow, so it is difficult to accept the intervention of foreign genetic materials, which makes it difficult for conventional seed selection methods to obtain excellent new varieties with new genetic variation. Therefore, in the future, modern biotechnology must be applied to actively develop new varieties with early maturity and fresh food, so as to improve the variety structure of longan in China and enhance its competitiveness in the international market. (2) The backward storage and preservation technology and low processing rate have seriously restricted the export and benefit of longan products. Longan ripens at high temperature in summer and autumn, and the fresh fruit decays within 5-6 days after harvesting, which is difficult to keep fresh and sell, and often causes social problems of rich fruits and poor farmers. With the rapid increase of longan production and the development of market economy, longan storage and preservation technology has become a hot research topic in China. Especially since 1980s, due to the progress of postharvest physiology research of longan, the comprehensive technology of low temperature storage and cold chain transportation and marketing has gradually matured, and longan storage and preservation has been applied to the marketing of fresh longan. At the same time, the development of processed products such as fruit juice, health care products and fruit wine, which cater to the trend of fresh and low sugar consumption, is still very backward. Therefore, it is necessary to vigorously strengthen the research and development of new technologies and products for fresh fruit remote preservation and processing, so as to rush out of the country and go to the world. (3) vigorously demonstrate that labor-saving cultivation is an effective way to reduce production costs, and advocate the construction of ecological longan orchard. At present, China's economy is underdeveloped, people's living standards are relatively low, and the growth of consumption is lower than the growth of fruit quantity, especially when the fresh fruit storage and preservation technology has not broken through the current situation. It is predicted that the sales price of longan in China will only remain at the current level in the future. In addition to strengthening management and improving the yield and quality of longan, we should also strengthen the ecological construction of longan orchards and strive to reduce production costs, otherwise maintaining small profits or unprofitable management for such a long time will definitely dampen the enthusiasm of planting fruits. Over the years, Chinese scientific and technological workers have made many achievements in the research of practical technology and applied basic theory of longan, which has promoted the rapid development of longan industry and summarized a set of mature labor-saving standardized cultivation techniques:
(1) Soil and water conservation technology of terraced fields such as orchards, planting leguminous green manure and less tillage.
② Implement nutrition diagnosis, concentrate formula fertilization and increase the application of organic fertilizer and micro-fertilizer.
③ Water-saving technology of grass mulching, corpse mulching or plastic film mulching.
(4) Targeted integrated control technology focusing on the prevention and control of ghost broom disease, emphasizing clearing the garden in winter to eliminate the source of overwintering pests and diseases, eradicating the first generation of pests and diseases in spring, and controlling litchi stinkbug and psyllid; Use more mineral pesticides and less chemical pesticides; Advocate the technology of combining agricultural cultivation with chemical control.
⑤ Advocate happy plastic surgery, and vigorously promote pruning, fruit thinning and fruit connecting technology.
⑥ Applying chemical control technology of plant growth regulators.