| China is the origin center of litchi (litchi chinensis Sonn.) and important commercial production region in the world. Litchi trees are widely distributed in the rainforest of Hainan island located in the south of China to the Yangtze river. There were abundant germplasm resources in China with a long history, more than2000years. During the recent decades, the study on the germplasm resources of litchi were mainly concentrated on the southern area including Guangdong, Hainan province and the Guangxi autonomous region of China. However, the upper reach of Yangtze river, as well as the north boundary of litchi distribution is another special area with a long history of litchi cultivation. There was rarely research on the litchi germplasm resources distributed especially in the lower reach of Minjiang river, one tributary of the Yangtze river. The basic research on litchi germplasm resource was extremely necessary for breeding and local litchi industry. Hence, an investigation on the distribution of the germplasm resource was carried out from2006-2011in the lower reach of Minjiang river. The classification for the old litchi trees was studied according to the fruit characteristics. The genetic diversity of these litchi germplasm was analyzed by Sequence-related amplified polymorphism (SRAP). And the investigation was carried out for cultivar introduction from Hejiang county, Sichuan province. The main results were as follow:1. The distribution of the ancient litchi trees in the lower reach of Minjiang river was mainly in the center district, Shawan county of Leshan city, the Qianwei county, Jiajiang county and Hongya county, which located in from29°05’N to29°48’N. At last, six hundred and fifty eight ancient litchi trees were found. This district belongs to the narrow valley area along the Minjiang river and its tributaries as Dadu river and Qingyi river. However, there was no living litchi trees in the district such as Chengdu, Meishan, Yaan city where litchi trees were found long before. According to the characteristics of the fruit exocarp, these germplasms could be classified into6types including Gulv, Hejianghebaoli, Wupao, Zhuanwozi, Bailizi, and Suanliz. Two of them characterized with the protruding and hard protuberances. Two of them were belong to the group which the protuberances were sparse or hairlike, fine or sharp pointed. Two of them were in the group which the protuberances were smooth or not evident.2. The ancient litchi trees found in the lower reach of Minjiang river characterized with tall plant above10m, developed roots system and thick canopy. These ancient trees were above100years old, and the oldest one may be over300years. The largest trunk girth was3.05m. The pinnate is with3-5pairs leaflet arranging opposite or alternate. The length of the leaflet varied from7cm to15cm and the width of the leaflet varied from2.5cm to5.0cm. The florescence of the ancient litchi was from the early April to the early May.The maturity date focused on from the late June to the middle of July.The shape of the fruits collected from the ancient litchi trees showed oval, heart, long-egg round, nearly round, ellipse and etc. The color of the fruit exocarp appeared red, dark-red, yellow and combined colors as red-yellow, red-green and others. The average fruit weight varied from9.2g to25.5g. The edible rate of the fruits varied from44.3%to72.5%.The rate of aborted seed was0%-30%. The vitamin C content of fruit juice was between25mg/100ml to39mg/100ml.3. In the present paper,41samples collected from the ancient litchi trees and3another cultivars including Hejiang dahongpao, Hejiangnuomici and Nanmuye introduced from Hejiang county, Sichuan province were analyzed with SRAP (Sequence-related amplified polymorphism). Thirty-two SRAP primer combinations were used and182polymorphic bands out of222were observed with an average of5.6per primer combination. The genetic diversity ranged from0.0329to o.4990, with an average level of0.2913. The unweighted pairgroup method arithmetic average (UPGMA) analysis demonstrated that the accessions had a similarity range from0.5586to0.9279with a mean value of0.7913. And there were four clusters at the similarity level of0.6700, indicating more extensive genetic variation among ancient trees. The cluster analysis results showed that the ancient litchi resources in lower reach of Minjiang river might share close relationship each other. Nevertheless, the Sul(Gualv) collected from Zhangba village, Suji town could be singly classified one group. The others as Hejiang Hebaoli,Wupao, Zhuanwozi, Bailizi, and Suanlizi were clustered in the other2groups. The cluster analysis indicated that there might be more litchi types among the ancient litchi trees. It was certain that there could be some special germplasm resources of litchi in the lower reach of minjiang river valley for further breeding and biodiversity conservation. The Clustering analysis showed that the three cultivars introduced from Hejiang county including Hejiang Dahongpao, Hejiang nuomici and Nanmuye were distinctly separated from the ancient trees and could be classified into the same group at the0.6700level for similarity.4. Four cultivars including Hejiang Dahongpao, Hejiang Nuomici, Luwo and Nanmuyewer were introduced from Hejiang county in1980s,1990s respectively. The investigation on biological and agronomical characteristics demonstrated that Hejiang Nuomici, Dahongpao,Luwo and Nanmuye litchi trees could show normally growth and development. However, the Luwo was fruitless, amd Hejiang Nuomici suffered from severe pest disease. Comparably, the Hejiang Dahongpao was the best one among the introduced cultivars with flowering in April and maturing in July. As for16-years-old tree, the average fruit yield of per tree, average weight per fruit fringe and per fruit weight were54Kg,860g and26g, respectively. Also Nanmuye, a late mature cultivar of23years old, produced fruits in the mid-August with mean weight25Kg per tree,518g per fruit cluster and18.5g of per fruit.The introduced cultivars could often generate shoots for several times in one year, but developing irregularly. The shoots germination, the formation of inflorescence and the process of fruiting from different types of shoots had been investigated. Traditionally, the shoots generated in spring and summer were the bearing fruit branch. The investigation results showed that the shoots generated in the late summer and early autumn which formed inflorescence easily and bear more fruits than other type of shoots.5. The main species and epidemiologic characteristics of litchi pests in the lower reach of Minjiang river were also investigated. Fourteen species of litchi pests were found, belonging to insecta,5items,7families,13species and arachnida,l family,1species. The main pests including Conopomorpha sinensis Bradley, Tessaratorna papillosa (Drury), Anoplophora macularia (Thompson) were the serious threaten to the local litchi industry. |
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