Analyzed On Genetic Diversity, Collection And Evaluation Of Fingered Citron

Fingered citron (Citrus medica L. var. sarcodactylis Swingle) is a specific Citrus in China and Southeast Asia, which has high market potential due to its medicinal properties, ornamental and nutritional values. Many local Fingered citron varieties were developed during the long cultivation history. However, it has narrow genetic background, as being without seed in fruits, asexual propagation methods were the main breeding way for this citrus. The continually asexual propagation results in genetic deterioration. Thus, the collection and evaluation of the Fingered citron germplasm is very important for its healthy and sustainable developments.At present, twenty Fingered citron and Citron materials have been collected and fourteen recouces have been cultivated in the germplam resources garden. The genetic diversities of twenty Fingered citron and Citron materials were analyzed by ISSR marker. One hundred and two bands were amplified with 11 polymorphic primers screened from 100 random primers. They contained 58 polymorphic ones and the polymorphism percentage was 56.9%. The genetic similarity ranged from 0.6078 to 0.9901 among all the materials. At the level of 0.798, all the materials may be separated into three groups. The genetic similarity ranged from 0.8431 to 0.9901 among Fingered citron strains. It indicated that there was low genetic diversity among Fingered citron strains.Qingpi and Aihua are two main cultivars in Jinhua area, the fruits of these two cultivars with different ripening status were harvested and cut into exocarp part and mesocarps part. Then, the content of total phenolics, flavonoids, vitamin C, carotinoids, and the antioxidant capability were determined. The contents of total phenolics, flavonoids, vitamin C in exocarp were significantly higher than in mesocarp of two Fingered citron (p<0.05 in all cases). However, the content of soluble sugar in mesocarp was higher than in exocarp (p<0.05 in all cases). Also, the total antioxidant capacity in exocarp was significantly higher than in mescarp (p<0.05 in all cases). In our study, little carotenoids was found in mesocarp of two cultivars, or even it exceeded the limit of detection. Along with the ripening process, the level of carotenoids was decreased; meanwhile, the contents of total phenolics, flavonoids, soluble sugar in two cultivars were generally increased. Similar to vitamin C, the total antioxidant capacity in exocarp raised gradually from August to November. The correlation coefficient (r) between total antioxidant capacity (determined by T-AOC detected box and FRAP) and phenolics, flavonoids, and vitamin C ranged from 0.9092 to 0.9920.To compare the nutritional quality between Fingered citron and Citron, Fingered citron's relative species, the contents of soluble sugar, starch, amino acid, protein, vitamin C, total phenolics, carotenoids, flavonoids, total antioxidant capacity were analyzed in exocarp and mesocarp of three Fingered citron strains and two else Citron strains. The contents of nutritional components among all the fruits lack of obvious rules. The results showed that the contents of starch, amino acid, protein, total phenolics, flavonoids, vitamin C, total antioxidant capacity and hydroxyl radical scavenging activity in exocarp was significantly higher than those in the mesocarp, whereas the contents of sugar was significant lower than those in the mesocarp. Specifically, the content of soluble sugar in exocarp and mesocarp of Zhoupi Citron was higher than the others. Highest content of starch and lowest amino acid were found in Yun Fingered citron. The highest content of carotenoids was detected in exocarp of Zhou pi Citron, with the value of 6.07 mg/100g FW. The contents of flavonoids, total phenolics and antioxidant capacity in the whole fruit of Zhoupi Citron, Huapi Citron and Yun Fingered citron were higher than Qingpi and Aihua Fingered citron. Among the three Fingered citrons, the content of vitamin C in exocarp of Yun Fingered citron was significant lower than other two Fingered citrons. However, the content of vitamin C in mesocarp of Yun Fingered citron was significant higher than the other two Fingered citrons, with the value 40.19mg/100gFW. The total antioxidant capacity in exocarp of Yun Fingered citron was significantly higher than the others.To screen the drought endurable rootstocks, the two-year-old seedlings grafted on five different rootstocks were selected for our study. The result showed that the compatibility between scions and Citron, Fingered citron were higher than the others. The leaf relative water content, chlorophyll content, the net photo synthetic rate, the maximum efficiency of PS II photochemistry (Fv/Fm), the effective PSⅡquantum yield ((?)psⅡ), the photochemical quenching (qp) and the electron transport rate (ETR) were reduced along with the prolonged drought stress, whereas the MDA, relative conductivity, minimum fluorescence yield (F0) and the non-photochemical quenching (qn) were generally increased in different degree. However, the increase and decrease levels differed significantly among the five grafted citrons, which indicated the different drought-resistant ability. The variation range of all the photosynthetic characters in lemon was lower than the four others. Considering the difference on biomass, between the two grafted seedling with high biomass, the damage to seeding grafted on Fingered citron was serious than seedlings on Citron. Meanwhile, among the grafted seedlings with low biomass the damage to seedlings grafted on huyou was higher than the ones on trifoliate and lemon.