| Chinese gallnut is a type of abnormal growth (gall) on the leaves or petioles of sumac trees (Anacardiaceae: Rhus,) which is produced by the gall aphids (Pemphigidae: Fordinae). It is an important insect resource and a traditional export product of China. It can be used as a raw material of industrial and has been widely used in medicine, textile, chemical industry, food, electronics industry, environment protection, and agriculture purposes. The horned gallnut which is making by Schlechtendalia chinensis is the main kind among all 14 gallnuts. Its yield is roughly occupied 75% of the total Chinese gallnut yield.Fourteen horned gallnut samples from seven provinces or cities which are in the main producing areas of Chinese gallnut were collected. Different characteristics including size, wall thickness, density, tannin and gallic acid were compared to evaluate the quality of horned gallnut. The correlations among the content of tannin, gallic acid and the environmental factors were analyzed in order to find out the main factors which affect the content of tannin and gallic acid. The research might lay a foundation for breeding new horned gallnut varieties and introducing of aphids. The genetic diversity of 14 geo-populations of S. chinensis were analyzed using 6 SSR primers. Genetic differentiations and correlations between genetic distance and geographic distance were analyzed in order to lay a theoretical foundation for genetic breeding of the gallnut aphids. The main results are as follows:1. The shapes, size, horn-like projection of the gallnuts from different producing areas are various. Some gallnuts hardly have horn-like projections and like balsl such as from Emei and Zhushan. Some have few horn-like projections and like pears, such as from Sangzhi and Taijiang. The others are irregular and have more horn-like projections such as from Suiyang, Yongding and Yanjin. The shape of gallnuts formed by the aphids which were introduced from other areas is similar to the original galls. It is indicated that the shape of gallnut is determined by the aphids.2. The tannin contents ranged from 61.59% to 68.30% and the average was 64.49%. From low to high were followed: Yinjiang<Xixiang<Zhushan<Guzhang<Yanjin<Sangzhi< Taijing<Yongding<Meitan<Wufeng<Suiyang<Wanyuan<Emei<Youyang. Gallic acid content ranged from 70.35% to 77.61% and the average was 73.92%. From low to high were followed: Yanjin<Zhushan<Xixiang<Yinjiang<Guzhang<Sangzhi<Taijing<Yongding<Meitan<Suiyang<Wufeng<Emei<Youyang<Wanyuan. Wall thickness of galls ranged from 1.55 to 2.01 mm and the average was 1.74 mm. Density ranged from 0.16 to 0.33 g/mL and the average was 0.26 g/mL. Correlation analysis indicated that tannin content had a positive significant correlation with the gallic acid content, but tannin and gallic acid contents had no significant correlations with wall thickness and density, respectively. Meanwhile, both of tannin and gallic acid contents had a negative significant correlation with monthly mean temperatures of April to August and had no significant correlations with the relative humidity, precipitation, and sunshine duration. It was suggested that temperature is the important factor which affected the quality of horned gallnut. The cluster analysis showed that 14 gallnuts samples were divided into 3 quality groups which stood for excellent, moderate and common categories.3. Eighteen polymorphic locus were detected with 6 SSR primers and the average was 3. The percentage of polymorphic bands (PPB) was 100%. For these geo-populations, the percentage in polymorphic loci was from 83.33% to 100% with an average of 99%. The number of alleles (Na) ranged from 2.0000 to 2.6667 with an average of 2.3572. The effective number of alleles (Ne) ranged from 1.7664 to 2.1582 with an average of 1.9884. The observed and expected heterozygositiy ranged from 0 to 0.1556 and 0.3770 to 0.5423, respectively. The Nei′s gene diversity and Shannon information index (I) ranged from 0.3652 to 0.5242 and 0.5725 to 0.8197. Genetic identity ranged from 0.7150 to 0.9653 and genetic distance ranged from 0.0353 to 0.3355. The genetic diversity of S. chinensis populations was low and a certain extent genetic differentiation among the populations had emerged.4. AMOVA analysis showed that there were 7.88% of the total variations among populations, 92.12% presented within populations. Mantel test revealed that there were no significant correlation between genetic distance and geographical distance (r=0.1766,P=0.094>0.05). UPGMA clustering analysis based on Nei (1972) indicated that there were two groups among 14 geographic populations. The first group was separated irregularly and distrbuted at both of the north and south of the Yangtze River. However, the second group was gathered at the south of the Yangtze River. It showed that genetic differentiation rarely caused by geographical isolation.5. According to the different characteristics of horned gallnut and the genetic diversity of S. chinensis geo-populations, 10 producing areas including Taijing, Suiyang and Meitan in Guizhou Province, Emei and Wanyuan in Sichuan Province, Guzhang and Yongding in Hunan Province, Zhushan in Hubei Province, Youyang in Chongqing City were choosen to build up horned gallnut core collection bank, which stood for the resource of Chinese horned gallnut. |
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