Prunus Sibirica Research Articles

Genetic diversity of Prunus sibirica L. superior accessions based on the SSR markers developed using restriction-site associated DNA sequencing

Prunus sibirica (Siberian apricot) has ecological, economic, and social benefits that makes it an important fruit-bearing tree in China. However, current fruit yields are low and unstable, thus restricting development of Prunus sibirica industry. To provide a scientific basis for successful breeding research aimed at developing superior cultivars, 98 screened SSR markers were first used in our study, developed by restriction-site associated DNA sequencing, to assess the genetic diversity of 66 Prunus sibirica accessions collected from four populations. The average number of alleles per locus (9.910) and the number of effective alleles (5.445) showed high polymorphism in the entire population, and the polymorphism information content (0.675) indicated that these markers were highly polymorphic. There was gene flow among the Prunus sibirica accessions, however the genetic differentiation coefficient showed 15.4% gene frequency differentiation among the provenances. Meanwhile, extensive linkage disequilibrium (D′ > 0.5, P < 0.01) was found, however the overall level was low (r2 < 0.5, p < 0.01). Additionally, the 66 accessions clustered into four groups, and these groups were extremely significantly correlated with the provenances classification. The clustering results showed that geographical distribution and genetic diversity changed from high to low as the geographic separation between provenances increased. Furthermore, population structure analysis supported these findings as genetic structure and provenances were extremely significantly correlated (p < 0.01). Additionally, the relationships between the geographical and genetic distances of the provenances and of the individuals were significantly correlated, indicating that geographical isolation importantly influenced Prunus sibirica evolution. The geographic and genetic effects underlying the superior accessions which we selected provide a reference for future molecular marker assisted breeding of Prunus sibirica.

Screening of optimal reference genes for qRT-PCR and preliminary exploration of cold resistance mechanisms in Prunus mume and Prunus sibirica varieties.

Prunus sibirica and Prunus mume are closely related plant species that differ in cold tolerance. Hybrids of P. sibirica and true mume, belonging to the apricot mei group, inherited strong cold resistance from P. sibirica. These materials are favourable for research on the molecular mechanisms of cold resistance. However, no suitable reference genes have been identified for analysing gene expression patterns between P. sibirica and P. mume. Ten candidate reference genes were assessed, namely, actins (ACT2-1, ACT2-2, ACT2-3, ACT2-4), protein phosphatase 2A-1 (PP2A-1), ubiquitins (UBQ2, UBQ3), ubiquitin extension protein (UBQ1) and tubulins (TUB1, TUB2), with four distinct algorithms (geNorm, NormFinder, BestKeeper and RefFinder). UBQ2 was recognized as the best reference gene in stems and buds across materials (P. sibirica; 'Xiaohong Zhusha', 'Beijing Yudie', and 'Xiao Lve' for true mume; and 'Dan Fenghou', 'Fenghou', and 'Yanxing' for apricot mei) under cold stress. In addition, the temporal and spatial expression patterns of PmCBF6 and PmLEA10 among seven varieties during winter periods were analysed using UBQ2 as a reference gene. The expression differed significantly among cultivars, which may contribute to their differences in cold tolerance. This paper confirmed the strong cold tolerance of apricot mei. And the best internal reference gene suitable for seven varieties was selected: UBQ2. Based on the above results, the expression of PmCBF6 and PmLEA10 genes during wintering in seven varieties was analysed. The molecular mechanisms of cold resistance were found to be possibly different in different varieties of P. sibirica and P. mume.

Effects of exogenous abscisic acid on oil content, fatty acid composition, biodiesel properties and lipid components in developing Siberian apricot (Prunus sibirica) seeds

Previous studies in Siberian apricot (Prunus sibirica) seed kernel (SASK) have suggested the involvement of abscisic acid (ABA) signaling pathway in oil accumulation. However, there are few reports on the effects of ABA on the metabolism of fatty acids (FA) in seed development. Here, we first evaluated the response of developing SASK to ABA treatment, with a focus on oil content, FA composition, biodiesel properties, lipid compounds and gene expressions. Compared with control samples, the application of exogenous ABA increased the total oil content by 6.55% in mature SASK. The C18:1 content markedly increased in ABA treatment, and conversely C16:0 decreased. Exogenous ABA also improved the biodiesel properties of SASK oil, making it better suited to the specifications of biodiesel standards. Furthermore, the molecular species of phosphatidylcholine (PC), phosphatidic acid (PA), diacylglycerol (DAG) and triacylglycerol (TAG) were detected using lipidomics analysis. The 18:1/18:1 was the main component in PA, PC and DAG, while the main components of 18:1/18:1/18:2, 18:1/18:1/18:3, 18:2/18:2/18:2 and 18:1/18:1/18:1 in TAG. Most lipid species gradually increased with SASK maturity. In addition, the relative contents of TAG-18:1/18:1/18:2 and TAG-18:1/18:1/18:1 in developing SASK increased with the application of exogenous ABA. We also detected elevated gene expression of key genes involved in ABA chemical pathway, which likely affected FA biosynthesis and accumulation. Our results provide insight into the effects of ABA on the oil accumulation in developing SASK, which has direct applications to improving the quality of SASK-derived biodiesel.

Photosynthetic CO&lt;sub&gt;2&lt;/sub&gt; response to soil water and its simulation using different models in leaves of two species

CO2 concentrations and soil moisture conditions are important factors in photosynthesis of trees. This study investigated the photosynthetic CO2 responses in the leaves of Prunus sibirica L. and Pinus tabulaeformis Carr. under eight soil water conditions in a semiarid loess hilly region. CO2-response curves and physiological parameters were fitted using a rectangular hyperbola model, nonrectangular hyperbola model, exponential equation, and modified rectangular hyperbola model. Results revealed the relative soil water content (RWCs) for P. sibirica required to maintain higher photosynthetic rate ranging from 46.5 to 81.6%, and that for P. tabulaeformis ranging from 35.4 to 84.5%. When RWCs exceeded these ranges, the net photosynthetic rate of both species decreased. CO2-response curves and three parameters, carboxylation efficiency, CO2-compensation point, and photorespiration rate, were well fitted by the four models when RWCs was appropriate for P. sibirica and P. tabulaeformis. When RWCs exceeded the optimal ranges, only the modified rectangular hyperbola model could precisely simulate the CO2-response curves and photosynthetic parameters of both species.

Using lipidomics to reveal details of lipid accumulation in developing Siberian apricot (Prunus sibirica L.) seed kernels

AbstractSiberian apricot seed kernel (SASK) contains a high of 50% oil with suitable fuel properties conformed to biodiesel standard. To date, Prunus sibirica is a novel non‐crop feedstock for biodiesel production in China. Here, oil contents and fatty acid (FA) compositions were identified in developing SASK from AS‐80 and AS‐84, at intervals of 1 week from 3 weeks after anthesis (WAA) to 9 weeks. The major differences in oil content between C18:1 and C18:2 levels were greater among the AS‐80 (32.69/15.48 g/100 g) than among the AS‐84 (25.78/13.15 g/100 g). Subsequently, the SASKs from 4, 6, and 8 WAA, respectively, representing early, middle, and late phases of oil accumulation, were selected as optimal samples for lipidomics analysis. It was notable that 18:1/18:1/18:2, 18:1/18:1/18:3, and 18:2/18:2/18:2 were the prominent compositions in triacylglycerol (TAG), and their higher content found among the AS‐80 was consistent with FA results. Although phosphatidic acid (PA) is directly connected with diacylglycerol (DAG) in Kennedy pathway, we found significant difference between PA and DAG compositions. The resulting molecular species differ in acyl composition depending on whether they were generated via phosphatidylcholine (PC) or Kennedy pathway. By qRT‐PCR analysis, the expression levels of FAD3, PDCT, and DAG‐CPT related to the biosynthesis of polyunsaturated fatty acids (PUFAs) showed a gradual decrease with SASK mature, explaining the drastic change of DAG‐18:3/18:3 content. Additionally, the lipidomics data coupled with qRT‐PCR analysis suggested that phospholipid:DAG acyltransferase may play a critical role in incorporation of PUFAs into sn‐3 of TAG. Our data contribute significantly to understand the underlying mechanisms of lipid accumulation in P. sibirica, and may also present strategies for engineering oil accumulation in oilseed plants.

Genetic diversity, population structure, and relationships of apricot (Prunus) based on restriction site-associated DNA sequencing

Single-nucleotide polymorphisms (SNPs) are the most abundant form of genomic polymorphisms and are widely used in population genetics research. Here, high-throughput sequencing was used to examine the genome-level diversity, population structure, and relationships of apricot, which are important for germplasm conservation and molecular breeding. Restriction site-associated DNA sequencing (RAD-seq) was adopted to sequence 168 Prunus spp. accessions distributed in five ecological groups, including 74 accessions of cultivated Prunus armeniaca L. and 94 accessions of wild apricots (P. armeniaca L. and Prunus sibirica L.), which generated 417,961 high-quality SNPs. We used cluster, genetic structure, and principal component analyses to examine the genetic diversities and genetic relationships of the 168 accessions. The Dzhungar-Ili ecological group accessions showed the highest genetic diversity in terms of private allele number, observed heterozygosity, and nucleotide diversity. We speculate that the Central Asian ecological group accessions were domesticated from the Dzhungar-Ili ecological group accessions. The population structure and gene flow of the North China and European ecological group accessions suggested a genetic background of P. sibirica. We argue that the two groups should be considered hybrid swarms connected to P. sibirica by continuous and extensive gene flow. P. armeniaca originated in Northwest China (Ili Valley), subsequently spread throughout Central Asia, and eventually spread to Europe. In addition, selective sweep signatures in P. armeniaca during domestication from wild to cultivated apricots, combined with differentially expressed genes, underlie distinct fruit traits, including sugars, aromas, organic acids, and carotenoids. This study provides substantive and valuable genomic resources that will significantly advance apricot improvement and effective utilization.

Pollen morphology of selected apricot (Prunus) taxa

The purposes of this study were to provide palynological information about apricots and to reveal the relationships among six ecological groups of apricots by describing the morphological characteristics of their pollen. The pollen grains of 175 accessions belonging to three species (Prunus armeniaca L., Prunus sibirica L., and Prunus mume Sieb. et Zucc.) of Prunus were examined using light microscopy and scanning electron microscopy. The pollen grains were isopolar monads, radially symmetric, medium to large in size, prolate or subprolate, and 3-colporate. Most pollen grains exhibited striate exine ornamentation, and a few exhibited striato-reticulate or cerebroid exine ornamentation. Cluster analysis divided the six ecological groups into two groups: one including the Central Asian, North China, and Dzhungar-Ili ecological group accessions and another including the Northeast Asian, European, and East China ecological group accessions. Principal component analysis revealed that equatorial diameter, colpus length, colpus width, and ridge width were the most important metrical pollen traits, and can be used as powerful diagnostic characters in apricot identification. We speculated that the cultivated apricots in Xinjiang were domesticated from wild apricots from the Ili Valley. This study describes the morphological characteristics of apricot pollen grains and provides some morphological information for future studies on the phylogenetic relationships of apricots.

The complete chloroplast genome sequence of Prunus sibirica

In this study, the chloroplast genome sequence of Prunus sibirica was obtained from the whole genome sequencing data of Prunus sibirica. Its length is 158,248 bp, which consists of 86,331 bp large single-copy region (LSC), 26,408 bp two reverse repeat regions (IR) and 19,101 bp small single-copy region (SSC). GC content of the whole chloroplast genome is 36.71%. Those of LSC region, SSC region, and IR region were 35, 30, and 43%, respectively. There are 131 unique genes in the chloroplast genome, including 90 protein-coding genes, 33 tRNA genes, and 8 rRNA genes. A maximum-likelihood phylogenetic tree was generated from the chloroplast genomes of 10 species of Rosaceae and 11 peripheral plants. The results showed that Prunus sibirica belongs to Rosaceae and is sister to Prunus salicina.

The complex evolutionary history of apricots: Species divergence, gene flow and multiple domestication events.

Domestication is an excellent model to study diversification and this evolutionary process can be different in perennial plants, such as fruit trees, compared to annual crops. Here, we inferred the history of wild apricot species divergence and of apricot domestication history across Eurasia, with a special focus on Central and Eastern Asia, based on microsatellite markers and approximate Bayesian computation. We significantly extended our previous sampling of apricots in Europe and Central Asia towards Eastern Asia, resulting in a total sample of 271 cultivated samples and 306 wild apricots across Eurasia, mainly Prunus armeniaca and Prunus sibirica, with some Prunus mume and Prunus mandshurica. We recovered wild Chinese species as genetically differentiated clusters, with P.sibirica being divided into two clusters, one possibly resulting from hybridization with P.armeniaca. Central Asia also appeared as a diversification centre of wild apricots. We further revealed at least three domestication events, without bottlenecks, that gave rise to European, Southern Central Asian and Chinese cultivated apricots, with ancient gene flow among them. The domestication event in China possibly resulted from ancient hybridization between wild populations from Central and Eastern Asia. We also detected extensive footprints of recent admixture in all groups of cultivated apricots. Our results thus show that apricot is an excellent model for studying speciation and domestication in long-lived perennial fruit trees.

HunShanDaKe sand east edge of vegetation ecological niche and interspecific association studies

Plant communities show some kind of interspecific relationship and different niche characteristics through the sharing and competition of resources in the living environment, which is of great significance for interpreting the response mechanism of vegetation to the environment. This study analyzes the niche breadth, niche overlap, and interspecific relationships of plant species in the study area by using ecological statistics. Although there are certain correlations among the species in the Hunshandake Sandy Land, the relationship is relatively loose and the whole is in an unstable stage; the plants with relatively wide niche under three types of site types in the eastern margin of the Hunshandake Sandy Land The species are Quercus mongolica (Betula platyphylla), Malus baccata + Spiraea pubescens, Ribes diacanthum (Ostryopsis davidiana) of the leeward slope; Ulmus pumila+ Ribes diacanthum and Siberian apricot (Ribes pulchellum ) on the windward slope; Ulmus pumila and Malus baccata + Spiraea trilobata, Rosa davurica (Kochia prostrata) on the hilly land. The combination of the leeward slope niche overlap is Betula platyphylla and Malus baccata + Spiraea pubescens, Ostryopsis davidiana; Ulmus pumila + Ribes pulchellum, Kochia prostrata on the windward slope; the hilly land for Malus baccata, Ulmus pumila + Spiraea trilobata.

WRINKLED1 transcription factor orchestrates the regulation of carbon partitioning for C18:1 (oleic acid) accumulation in Siberian apricot kernel

WRINKLED1 (WRI1), an APETALA2 (AP2)-type transcription factor, has been shown to be required for the regulation of carbon partitioning into fatty acid (FA) synthesis in plant seeds. To our knowledge, the regulatory network of WRI1 remains unknown in Prunus sibirica kernel (PSK), a novel woody biodiesel feedstock in China. In this study, based on the transcriptional data from developing oilseeds of multiple plant species, we identified 161 WRI1-coexpressed genes using weighted gene co-expression network analysis (WGCNA). The major portion of WRI1-coexpressed genes was characterized to be involved in carbon partitioning and FA biosynthesis. Additionally, we detected the temporal patterns for oil content and FA compositions in developing PSK from two different germplasms (AS-85 and AS-86). The major differences between the two germplasms are higher contents of oil and C18:1 in AS-85 than in AS-86 at a mature stage. Thus, AS-85 and AS-86 are desirable materials to explore the molecular and metabolic mechanisms of oil accumulation in Siberian apricot. Expression analysis in developing PSK of AS-85 and AS-86 indicated that the expression level of P. sibirica WRI1 (PsWRI1) was closely correlated to accumulative rate of oil. Also, the comparison of expression profiles in developing PSK of AS-85 and AS-86 displayed that the pPK, E1-α, E2, TAL, BC, MCMT, BS, SAD and FAD2 have a high correlation with PsWRI1. Transient expression showed that ProSAD- and ProBS-driving GUS expression showed no substantial difference between AS-85 and AS-86, while the expression level of ProPEPCK-AS-85 driving GUS was significantly higher than that of ProPEPCK-AS-86 driving GUS. Additionally, transient co-transformation with PsWRI1 revealed that ProSAD, ProPEPCK and ProBS activity could be specifically up-regulated by PsWRI1. This regulatory mechanism of PsWRI1 may create a steep concentration difference, thereby facilitating carbon flux into C18:1 accumulation in developing PSK. Overall, all our findings imply a versatile mechanism of WRI1 to optimize carbon allocation for oil accumulation, which can provide reference for researching the woody biodiesel plants.

Amino acid profiles and protein quality of Siberian apricot (Prunus sibirica L.) kernels from Inner Mongolia

Siberian apricot (Prunus sibirica L.) is a traditional nut tree species in East Asia and Siberia and is a possible contribution to healthy diets. However, it has attracted little research attention and information on the nutritional value of its kernel is limited. In this study, the profile, nutritional value and variation of amino acids were investigated in eight provenances. The kernels contained 29 × 10−2 g/g protein and were rich in glutamic acid (26.5%), aspartic acid (11.3%) and arginine (10.1%). They showed higher essential amino acids (EAA) than similar protein values for almonds. The variation coefficients of amino acids ranged from 3.8 to 43.7%, and the levels of seven amino acids were significantly different among the eight provenances. The proportion of essential amino acids to total amino acids and amino acid score were also quite different. Protein was negatively correlated with some amino acids and protein quality values. In conclusion, there were two superior provenances (Wanjiagou and Horinger County) with high EAA contents and protein quality, and could be used in the large-scale development of this species.

Comprehensive evaluation of fuel properties and complex regulation of intracellular transporters for high oil production in developing seeds of Prunus sibirica for woody biodiesel

BackgroundBased on our previous studies of 17 Prunus sibirica germplasms, one plus tree with high quality and quantity of seed oils has emerged as novel potential source of biodiesel. To better develop P. sibirica seed oils as woody biodiesel, a concurrent exploration of oil content, FA composition, biodiesel yield and fuel properties as well as prediction model construction for fuel properties was conducted on developing seeds to determine the optimal seed harvest time for producing high-quality biodiesel. Oil synthesis required supply of carbon source, energy and FA, but their transport mechanisms still remains enigmatic. Our recent 454 sequencing of P. sibirica could provide long-read sequences to identify membrane transporters for a better understanding of regulatory mechanism for high oil production in developing seeds.ResultsTo better develop the seed oils of P. sibirica as woody biodiesel, we firstly focused on a temporal and comparative evaluation of growth tendency, oil content, FA composition, biodiesel yield and fuel properties as well as model construction for biodiesel property prediction in different developing seeds from P. sibirica plus tree (accession AS-80), revealing that the oils from developing seeds harvested after 60 days after flowering (DAF) could be as novel potential feedstock for producing biodiesel with ideal fuel property. To gain new insight into membrane transport mechanism for high oil yield in developing seeds of P. sibirica, we presented a global analysis of transporter based on our recent 454 sequencing data of P. sibirica. We annotated a total of 116 genes for membrane-localized transporters at different organelles (plastid, endoplasmatic reticulum, tonoplast, mitochondria and peroxisome), of which some specific transporters were identified to be involved in carbon allocation, metabolite transport and energy supply for oil synthesis by both RT-PCR and qRT-PCR. Importantly, the transporter-mediated model was well established for high oil synthesis in developing P. sibirica seeds. Our findings could help to reveal molecular mechanism of increased oil production and may also present strategies for engineering oil accumulation in oilseed plants.ConclusionsThis study presents a temporal and comparative evaluation of developing P. sibirica seed oils as a potential feedstock for producing high-quality biodiesel and a global identification for membrane transporters was to gain better insights into regulatory mechanism of high oil production in developing seeds of P. sibirica. Our findings may present strategies for developing woody biodiesel resources and engineering oil accumulation.

Comparative transcriptome analysis identifies differentially expressed genes between normal and late-blooming Siberian apricot

Blooming date is an important trait in fruit tree species. Although several quantitative trait loci confirming blooming date were identified in Prunus spp., the molecular mechanism underlying it remains unclear. Arising from this, the transcriptomes of normal blooming and late-blooming Siberian apricot (P. sibirica L.) flower buds were analyzed using RNA-seq technology. A total of 68,855 unigenes were de novo assembled, among which 1204 were differentially expressed between normal and late blooming. Gene ontology enrichment analysis revealed that biological processes were enriched with metabolic processes. The catalytic-related gene transcripts between the two types of blooming were significantly changed in the molecular function. Kyoto Encyclopedia of Genes and Genomes pathway analysis showed that 156 genes were successfully annotated and 75 pathways enriched. Genes for gibberellin biosynthesis were up-regulated in normal blooming, whereas abscisic acid degradation-related genes were also up-regulated in normal blooming. Moreover, circadian rhythms related genes including EARLY FLOWERING 4, LATE ELONGATED HYPOCOTYL and CIRCANDIAN CLOCK ASSOCIATED1 were all up-regulated in normal blooming, indicating that circadian rhythms have a very important role in controlling blooming date. Furthermore, zinc finger protein CONSTANS-LIKE 12 was blasted onto the quantitative trait loci region on linkage group 4 in peach. However, changes in the abundance of key flowering genes such as SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1, FLOWERING LOCU T, LEAFY and FLOWERING LOCUS C were not significantly different, indicating that further investigation should explore the function of these genes on blooming date. The outcomes of this study will provide a valuable platform for further research on the molecular mechanism of blooming date in Prunus.

Identification of AUXIN RESPONSE FACTOR gene family from Prunus sibirica and its expression analysis during mesocarp and kernel development

BackgroundAuxin response factors (ARFs) in auxin signaling pathway are an important component that can regulate the transcription of auxin-responsive genes involved in almost all aspects of plant growth and development. To our knowledge, the comprehensive and systematic characterization of ARF genes has never been reported in Prunus sibirica, a novel woody biodiesel feedstock in China.ResultsIn this study, we identified 14 PsARF genes with a perfect open reading frame (ORF) in P. sibirica by using its previous transcriptomic data. Conserved motif analysis showed that all identified PsARF proteins had typical DNA-binding and ARF domain, but 5 members (PsARF3, 8 10, 16 and 17) lacked the dimerization domain. Phylogenetic analysis of the ARF proteins generated from various plant species indicated that ARFs could be categorized into 4 major groups (Class I, II, III and IV), in which all identified ARFs from P. sibirica showed a closest relationship with those from P. mume. Comparison of the expression profiles of 14 PsARF genes in different developmental stages of Siberian apricot mesocarp (SAM) and kernel (SAK) reflected distinct temporal or spatial expression patterns for PsARF genes. Additionally, based on the expressed data from fruit and seed development of multiple plant species, we identified 1514 ARF-correlated genes using weighted gene co-expression network analysis (WGCNA). And the major portion of ARF-correlated gene was characterized to be involved in protein, nucleic acid and carbohydrate metabolic, transport and regulatory processes.ConclusionsIn summary, we systematically and comprehensively analyzed the structure, expression pattern and co-expression network of ARF gene family in P. sibirica. All our findings provide theoretical foundation for the PsARF gene family and will pave the way for elucidating the precise role of PsARF genes in SAM and SAK development.

Updated breeding distribution and population status of Jankowski’s Bunting Emberiza jankowskii in China

SummarySince 2010, Jankowski’s Bunting Emberiza jankowskii has been listed as ‘Endangered’ on the IUCN Red List of Threatened Species. However, because no comprehensive surveys had been conducted, it was not known whether undiscovered populations existed elsewhere, so the population status of the species could not be assessed accurately. The aim of this study was to assess the breeding distribution and population size of Jankowski’s Bunting in China. Fifty sites in Inner Mongolia, and Jilin, Heilongjiang, Liaoning and Hebei Provinces were surveyed to locate suitable habitat and breeding populations of Jankowski’s Bunting. The surveyed sites included historical breeding distribution areas, wintering sites, and regions adjacent to historical breeding distribution areas. We confirmed that Jankowski’s Bunting has disappeared from most of its former breeding distributions, with the exceptions of Dagang, Xiergen and Tumiji. Additionally, 13 new breeding sites were discovered in Inner Mongolia. All currently known populations breed in Mongolian steppe-vegetation zones, with shrubs dominated by the natural Siberian apricot Prunus sibirica, indicating that this type of habitat is crucial for the survival of the species. Based on remote sensing, the suitable breeding habitat for Jankowski’s Bunting is estimated to be approximately 280 km2. The population size of Jankowski’s Bunting could range between 9,800 and 12,500 individuals, which is much higher than the numbers estimated in previous reports that were based on partial surveys. The suitable habitat remaining in Inner Mongolia would highly benefit from the implementation of the National Key Public Forest Protection Project. The population size of Jankowski’s Bunting is larger than previously estimated, but it is still threatened by habitat degradation and fragmentation, and our survey results reinforce the need for more research. The status of Jankowski’s Bunting in China still meets the IUCN criteria B2ab for an ‘Endangered’ species.

Phylogeography Study of the Siberian Apricot (Prunus sibirica L.) in Northern China Assessed by Chloroplast Microsatellite and DNA Makers.

There is evidence that a band of dry climate separated plants in East Asia into distinct northern and southern groups. However, few studies have focused on the arid belt in this region, especially with regard to plants. We analyzed genetic variation in 22 populations of Siberian apricot (Prunus sibirica L.), a temperate deciduous species distributed in this arid belt, using two chloroplast DNA (cpDNA) sequences, seven chloroplast microsatellite loci (cpSSRs), and 31 nuclear microsatellite loci (nSSRs), to study its phylogeography. Chloroplast data showed the complete fixation of two different genetic groups: the eastern and western groups. Genetic differentiation between the two groups was significant (FST = 0.90925, p < 0.01). This pronounced phylogeographic break was also indicated by nSSR data, but there were disparities regarding individual populations. An asymmetric gene flow via pollen and seeds likely resulted in discordance between the present-day geography of nuclear and chloroplast lineages. There was a distinct boundary between the two large groups, which were fixed for two of the most ancestral chlorotypes. Two populations with the highest chloroplast genetic diversity were located in the Yanshan Mountains and Jinzhou, considered to be the glacial refugia. The split of chloroplasts between the eastern and western groups was estimated to have occurred ~0.1795 Ma, whereas nuclear divergence occurred approximately 13,260 years ago. Linear regression analysis showed that climatic factors (annual precipitation and annual mean temperature) had a significant correlation with mean ancestry value (P < 0.05) indicated that they were potential factors for the formation of the two groups. In addition, this boundary was a contact zone between two groups from different refugia.

The genetic relationship and structure of some natural interspecific hybrids in Prunus subgenus Prunophora, based on nuclear and chloroplast simple sequence repeats

In the subgenus Prunophora of the genus Prunus, many transitional traits presented in interspecific hybrids, the so-called ‘new species’, were frequently named due to the complicated botanical classification system. In this study, we used 16 nuclear simple sequence repeats (nSSRs) and 10 chloroplast simple sequence repeats (cpSSRs) to evaluate genetic relationships among 42 accessions, which included 15 putative interspecific hybrids, and then to reveal the speciation and differentiation in the subgenus Prunophora. In total, 231 and 27 alleles were observed in nSSRs and cpSSRs respectively; and with cpSSRs 20 haplotypes were revealed among the accessions. Furthermore, the haplotype and genetic structure analysis implied that (1) Prunus simonii Carr. might be a subspecies or a forma of Prunus salicina L., rather than an interspecific hybrid between P. salicina and Prunus armeniaca L., (2) Prunus limeixing Zhang et Wang was derived from a natural hybrid with P. salicina as its maternal progenitor and P. armeniaca as the female parent, and (3) Prunus cathayana Fu et al. (or kernel-using apricot) was an interspecific hybridization species of P. armeniaca (maternal parent) and Prunus sibirica L. (female parent). These results will be useful for clarifying the problems in the botanical classification, and facilitate the conservation and management of plum and apricot genetic resources in the Chinese National Germplasm Repository for Plums and Apricots.

RELATIONS BETWEEN SOIL ORGANIC CARBON AND OTHER SOIL PHYSICOCHEMICAL INDICES UNDER DIFFERENT LAND USE PATTERNS

This paper investigates the relations between soil organic carbon (SOC) and other physicochemical indices in low hills of Chifeng, Inner Mongolia, and thus to help with soil modification in low hills there. Grey relational analysis and stepwise regression analysis were used to uncover the relations of SOC with total N (TN), pH, available P (AP), available K (AK), and microbial biomass carbon (MBC) under eight land use patterns in a typical small watershed in Chifeng. The eight land uses were Prunus sibirica land, Caragana microphylla land, Populus simonii land, Ulmus pumila land, natural grassland, Pinus Tableulaeformis [Formula: see text] P. sibirica mixed land, secondary forest of natural bush land, and agricultural land. The average SOC contents in the 0–100[Formula: see text]cm layer in the above eight land use patterns are 7.72, 5.32, 7.40, 6.11, 3.14, 10.26, 17.51 and 5.34[Formula: see text]g/kg, respectively, indicating significant differences. The relation coefficients of SOC with TN, pH, MBC, AK, and AP are 0.70, 0.66, 0.63, 0.57 and 0.55, respectively, under all land use patterns. SOC contents are significantly different among these land use patterns, and the relation coefficients of SOC with other physicochemical indices rank in the order as: [Formula: see text]. The optimum regression equation of SOC ([Formula: see text] with TN ([Formula: see text] and pH ([Formula: see text] was built: [Formula: see text], ([Formula: see text]).

Allelic variation of simple sequence repeats markers linked to PPV resistance in Chinese apricot

Apricot is one of the oldest fruit tree crops in China and it was spread via Armenia to other areas. There are about ten species of apricot (Subg. Armeniaca Mill.) worldwide, among which nine species are native to China. Sharka disease caused by the Plum pox virus (PPV) is widely distributed in the main producing regions of apricot. In this study, linked simple sequence repeats (SSR) primers were used to detect allele variations potentially associated with PPV resistance among Chinese apricot germplasm resources, including 52 accessions belonging to Prunus armeniaca, 7 to Prunus mandshurica, 6 to Prunus sibirica, 4 to Prunus mume, 17 to other species or types. The allelic variation at loci with PPV resistance showed that these SSR markers linked to PPV resistance kept a relatively high level of diversity in Chinese apricot. The special alleles and genotypes only found in South China cultivars might reveal new PPV resistance sources. Some famous local cultivars of Chinese apricot might be considered as candidates for PPV resistance.