A phylogenetic network of wild Ussurian pears (Pyrus ussuriensis Maxim.) in China revealed by hypervariable regions of chloroplast DNA

In order to understand the genetic diversity of wild Ussurian pears in China, chloroplast DNA (cpDNA) of 186 wild accessions from 12 populations in Inner Mongolia, Heilongjiang and Jilin Provinces and 51 Chinese and European pear cultivars including Pyrus ussuriensis, Pyrus pyrifolia, Pyrus bretschneideri, Pyrus sinkiangensis and Pyrus communis were investigated. Each accession was classified into one of three types (types A, B and C) based on two large deletions in the hypervariable regions between the accD–psaI and rps16–trnQ genes. Thirty haplotypes were identified by 32 mutations including 17 gaps (in/dels) and 15 base changes. Haplotype network analysis revealed that wild Chinese Ussurian pears could be grouped into subgroup I of type A. A haplotype, Hcp3, in subgroup I detected in Heilongjiang and Jilin Provinces was considered to be a divergent centre in Chinese Ussurian pears. However, the genetic diversity of wild accessions revealed by the two hypervariable regions was quite low. In particular, 98 % of wild Ussurian accessions in Inner Mongolia shared an identical haplotype Hcp1 and are, therefore, monomorphic. In comparison, Chinese pear cultivars were more divergent. These results suggest that the cpDNAs from wild Ussurian pears in Inner Mongolia have specifically differentiated compared to those from pears of other areas. The number of wild Ussurian pears has been decreasing because of desertification and land development, therefore conservation is needed.     

High-level phenotypic variations in populations of Armeniaca sibirica in Nei Mongol,China北大核心CSCD

Aims: Our objectives were to determine the variations in phenotypic traits of Armeniaca sibirica populations and their spatial patterns. Methods: We used nested variation, coefficient of variation, multi-comparison, correlation analysis and principal component analysis to analyze the 23 phenotypic traits for 130 individuals in 13 populations of A. sibirica. Important findings: The results showed that there were significant differences in phenotypic variations among and within populations. The variation was greater among populations (47.15%) than within population (16.43%). The mean phenotypic differentiation coefficient was 73.03% among populations, indicating the variance among populations being the main source of the phenotypic variation. The average variation coefficient of 23 traits ranged from 7.01% to 27.23%, with an average of 14.28%. The variation coefficient of nutlet was highest (15.67%), and the variation coefficient of fruit was smallest (12.11%). The phenotypic diversity is highest in Wanjiagou Tumotezuoqi and smallest in Horqin, Right Front Banner Chaersen. Longitude, mean annual precipitation and sunshine duration were significantly correlated with major traits of phenotypic. The 13 populations could be divided into four groups according to the principal component analysis. Leaf traits of Wula Mountain and nutlet traits of Archorchin Banner were significantly correlated with ecological and geographic factors.     

Association and Validation of Yield-Favored Alleles in Chinese Cultivars of Common Wheat (Triticumaestivum L.)

Common wheat is one of the most important crops in China, which is the largest producer in the world. A set of 230 cultivars was used to identify yield-related loci by association mapping. This set was tested for seven yield-related traits, viz. plant height (PH), spike length (SL), spikelet number per spike (SNPS), kernel number per spike (KNPS), thousand-kernel weight (TKW), kernel weight per spike (KWPS), and sterile spikelet number (SSN) per plant in four environments. A total of 106 simple sequence repeat (SSR) markers distributed on all 21 chromosomes were used to screen the set. Twenty-one and 19 of them were associated with KNPS and TKW, respectively. Association mapping detected 73 significant associations across 50 SSRs, and the phenotypic variation explained (R²) by the associations ranged from 1.54 to 23.93%. The associated loci were distributed on all chromosomes except 4A, 7A, and 7D. Significant and potentially new alleles were present on 8 chromosomes, namely1A, 1D, 2A, 2D, 3D, 4B, 5B, and 6B. Further analysis showed that genetic effects of associated loci were greatly influenced by association panels, and the R² of crucial loci were lower in modern cultivars than in the mini core collection, probably caused by strong selection in wheat breeding. In order to confirm the results of association analysis, yield-related favorable alleles Xgwm135-1A₁₃₈, Xgwm337-1D₁₈₆, Xgwm102-2D₁₄₄, and Xgwm132-6B₁₂₈ were evaluated in a double haploid (DH) population derived from Hanxuan10 xLumai14.These favorable alleles that were validated in various populations might be valuable in breeding for high-yield.     

施肥对内蒙古短花针茅荒漠草原土壤呼吸的影响

2012年在内蒙古短花针茅荒漠草原设置了3个N肥水平（2.5、5和10 g N·m^-2）的不同NPK配施样地,并以未施肥样地为对照(CK),采用LI 8100土壤碳通量测量系统测定了样地中土壤呼吸速率的日动态和季节变化,分析土壤呼吸速率与环境因子的关系.结果表明: 在植物生长旺盛期(8月),3个N肥水平中,10 g N·m^-2处理的土壤呼吸速率显著高于其他处理,5和2.5 g N·m^-2处理的土壤呼吸速率与CK无显著差异.在植物生长初期和中期(5—9月),施P肥有利于提高土壤呼吸速率.施肥并未改变荒漠草原土壤呼吸的日动态和季节变化特征.各处理日变化最高值和最低值分别出现在10:00—14:00和03:00—05:00;季节动态的峰值均出现在8月.土壤呼吸速率与5 cm土壤温度及0～10 cm土壤含水量显著相关,其决定系数分别在0.40～0.58和0.51～0.70,说明表层土壤含水量是制约土壤呼吸变化的主要环境因子.     

梨不同DNA提取方法的效果研究

以7个梨品种为实验材料,比较分析了SDS法、CTAB法、SDSCTAB法、改良的CTAB法、高盐低pH值法、分步离心法对梨总DNA提取的效果。结果表明:利用以上6种方法提取的梨总DNA在纯度和量上有很大的差别。所得到的平均DNA量从大到小依次为:分步离心法、SDS法、SDSCTAB法、改良的CTAB法、CTAB法、高盐低pH值法。DNA提取纯度依次为分步离心法、SDSCTAB法、改良的CTAB法、高盐低pH值法、CTAB法、SDS法。RAPD和自交不亲和基因(S基因)特异性引物扩增实验结果都比较理想,但分步离心法和SDSCTAB法提取的DNA双酶切效果较好。分步离心法提取的梨总DNA更适用于后续的分子生物学实验操作。     

Wheat genomic study for genetic improvement of traits in China

Science China Life Sciences - Bread wheat (Triticum aestivum L.) is a major crop that feeds 40% of the world’s population. Over the past several decades, advances in genomics have led to...     

Population Structure of and Conservation Strategies for Wild Pyrus ussuriensis Maxim. in China

Pyrus ussriensis Maxim. is native to the northern part of China, but whose habitats are currently being destroyed by environmental changes and human deforestation. An investigation of population structure and genetic diversity of wild Ussurian pear is a priority in order to acquire fundamental knowledge for conservation. A total of 153 individuals of wild Ussurian pear from the main habitats, Heilongjiang, Jilin, and Inner Mongolia in China, possessed low genetic diversity as a result of habitat fragmentation. The genetic diversity of the populations in Inner Mongolia and north east of Heilongjiang was especially low and there was the possibility of inbreeding. Wild Ussurian pears were divided into 5 groups based on the Bayesian clustering method using 20 nuclear SSRs (nSSRs) and 5 groups by haplotype distributions using 16 chloroplast SSRs (cpSSRs), and the populations in Inner Mongolia and north east of Heilongjiang represented unique genotypes. AMOVA indicated there was a 20.05% variation in nSSRs and a 44.40% variation in cpSSRs among populations. These values are relatively high when compared to those of other tree species. Haplotype E, positioned in the center of the cpSSR analysis network and showed the largest number of connections with other haplotypes, represented the most important haplotype. Inner Mongolia and the north east of Heilongjiang are two areas that need urgent conservation because of their genetic vulnerability and peculiarity. We determined 4 conservation units based on the clustering by nSSRs and cpSSRs, and geographic factor. This information is helpful in deciding the conservation strategies for wild Ussurian pear in China.     

Cloning, characterization and promoter analysis of S-RNase gene promoter from Chinese pear (Pyrus pyrifolia)

The 5'-flanking region of the S(12)-, S(13)-, S(21)-RNase with a length of 854 bp, 1448 bp and 1137 bp were successfully isolated by TAIL-PCR from genomic DNA from 'Jinhua', 'Maogong' (Pyrus pyrifolia) and 'Yali' (Pyrus bretschneideri) genomic DNA. Sequence alignment and analysis of S(13)-, S(12)-, S(21)-RNase gene promoter sequences with S(2)-, S(3)-, S(4)-, S(5)-RNase 5'-flanking sequences indicated that a homology region of about 240 bp exists in the regions just upstream of the putative TATA boxes of the seven Chinese/Japanese pear S-RNase genes. Phylogenetic tree suggests that the homology region between the Chinese/Japanese pear and apple S-RNase gene promoter regions reflects the divergence of S-RNase gene was formed before the differentiation of subfamilies. Full length and a series of 5'-deletion fragments-GUS fusions were constructed and introduced into Arabidopsis thaliana plants. GUS activity were detected in S(12)-pro-(1 to 5)-GUS-pBll01.2 transgenic pistils and progressively decreased from S(12)-pro-1-GUS-pBI l01.2 to S(12)-pro-5-GUS-pBll01.2. No GUS activity was detected in S(12)-pro-6-GUS-pBll01.2 transgenic pistil and other tissues of non-transformants and all transgenic plants. The result suggested S(12)-RNase promoter is pistil specific expression promoter.