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  • Author or Editor: Yu Zong x
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Pyrus betulaefolia is one of the most popular pear (Pyrus) rootstocks in China and other east Asian countries because of its good adaptability to versatile environments. However, the number of wild P. betulaefolia populations is decreasing because of habitat destruction and fragmentation. An urgent evaluation of P. betulaefolia genetic diversity and population structure is necessary to develop a conservation strategy for this important wild species. Thirteen simple sequence repeat loci were detected to infer the genetic composition of 18 P. betulaefolia populations in northern China. The average number of different alleles for each locus was 7.1. The number of effective alleles among loci ranged from 1.77 to 5.94. The overall mean values of expected and observed heterozygosity were 0.702 and 0.687, respectively. The Taihang Mountains, which run from northeast to southwest, acted as natural boundary in shaping the genetic diversity of P. betulaefolia in northern China. The distinct pattern, which was also observed in the distribution of chloroplast DNA (cpDNA) variation, appeared to be obscured by pollen-mediated gene flow in the distribution of nuclear microsatellite variation. Large populations with high allelic richness (e.g., populations BT, ZN, and QS) are considered suitable for in situ conservation because of the potential for adaptation to future environmental change. The smaller populations had mixed gene pools (e.g., populations GQ and XF) and should therefore also be considered for ex situ conservation. Preserving genetic diversity in seeds was proposed when field collections are fully characterized.

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Sugar and organic acid contents as well as sugar-to-acid ratio of fruit are important factors affecting fruit quality and processing. In this study, we compared sugar and organic acid contents of Vaccinium uliginosum (bog bilberry) fruit harvested from 100 plants across 10 wild populations growing in the Changbai Mountains of China. Correlation of sugar and acid contents with the spatial distribution of these populations was accessed. Germplasm with high sugar and low acid with potential for use in future breeding was also identified. Results showed that sugar and organic acid contents varied among different V. uliginosum populations in the Changbai Mountains. Fructose (18.60–38.54 mg·g−1) and glucose (15.77–35.08 mg·g−1) were the main sugars, whereas quinic (16.06–20.97 mg·g−1), citric (10.39–14.96 mg·g−1), and malic (4.28–7.47 mg·g−1) acids were the main organic acids in V. uliginosum. The first population collected in the Dongfanghong forest farm (lat. 42°00′N, long. 128°03′E) showed the highest average sugar content and sugar-to-acid ratio among the sampled populations. Moreover, total sugar content and sugar-to-acid ratio of Sample 7—Population 1, which is located at Manjiang forest farm (lat. 41°09′N, long. 127°05′E) was much higher than the other 99 samples, making this sample representative of important germplasm for breeding. Altitude and latitude were important environmental factors affecting sugar and organic acid contents. Fructose, glucose, and total sugar contents were positively correlated with altitude and negatively correlated with latitude. Oxalic acid content and sugar-to-acid ratio were positively correlated with altitude, and there was no significant correlation between organic acid contents and latitude.

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