Parthenocarpy largely depends on the coordinated action of hormones produced in unpollinated ovaries, but can be induced by application of exogenous hormones. We evaluated the effects of gibberellins (GA4+7) and 1-(2-chloro-4-pyridyl)-3-phenylurea (CPPU) on induction and quality of parthenocarpic fruit in Pyrus pyrifolia Nakai ‘Cuiguan’ pear. Parthenocarpic fruit with a small core and a high edible ratio were induced by GA4+7 and/or CPPU. GA4+7 application induced normally shaped fruit with superior quality and normal size, whereas CPPU treatments resulted in abnormally shaped fruit with a larger size and an extraordinarily expanded calyx tube. Among all GA4+7 treatments, 500 mg L−1 GA4+7 induced the highest fruit set (91.88 %) and increased fruit size by 85 % compared with fruit induced by 200 mg L−1 GA4+7. In addition, the parthenocarpic fruit induced by GA4+7 accumulated considerably higher quantities of sucrose and less organic acids than pollinated and CPPU-induced fruit. The potential commercial application of CPPU and GA to pear in place of hand pollination is discussed.

The role of chilling in bud dormancy release and biochemical changes in different organs were evaluated in stem cuttings of pear (Pyrus pyrifolia) cv. Cuiguan selected at the leaf fall. The cuttings were exposed to 5 °C for 0, 100, 200, 300, 400, 500, 600, and 700 chilling hours (named positive chill units; PCU). A 50 % bud break was observed in floral and vegetative bud cuttings at 300 and 600 PCU, respectively. A mean time to bud break was inversely proportional to the chilling treatment. The low-temperature stimulated starch hydrolysis accompanied with sucrose accumulation in all organs. Sucrose and sorbitol content increased substantially peaking at 100, 400, and 100 PCU in floral buds, vegetative buds, and bark, respectively, thereafter decreased when buds approached chilling satisfaction (300 and 600 PCU for the floral and vegetative buds, respectively), and then increased again up to 700 PCU. Hexoses (glucose and fructose) accumulated constantly in the buds from 0 to 700 PCU. In bark, glucose and fructose content increased up to 400 PCU, and then gradually decreased. Total amylolytic and α-amylase activities increased in all organs, especially in the floral and vegetative buds up to 100 PCU and then decreased in the floral and vegetative buds before increasing again after endo-dormancy release. Invertase activity remained high in the buds during chilling satisfaction possibly because of translocation of sucrose to the buds which functioned as a strong sink. The results suggest that a low availability of hexoses may be the cause of limited bud breaks due to lack of chilling. Chilling satisfaction of the buds may increase the content of soluble sugars and acid invertase activity, and decrease the starch content, which may correlate with improved bud breaks.

Interspecific hybridization has been considered the major mode of evolution in Pyrus (pear), and thus, the genetic relationships within this genus have not been well documented. Retrotransposons are ubiquitous components of plant genomes and 42.4 % of the pear genome was reported to be long terminal repeat (LTR) retrotransposons, implying that retrotransposons might be significant in the evolution of Pyrus. In this study, 1,836 putative full-length LTR retrotransposons were isolated and 196 retrotransposon-based insertion polymorphism (RBIP) primers were developed, of which 24 pairs to the Ppcr1 subfamily of copia retrotransposons were used to analyze genetic diversity among 110 Pyrus accessions from Eurasia. Our results showed that Ppcr1 replicated many times in the development of cultivated Asian pears. The genetic structure analysis and the unweighted pair group method with arithmetic mean (UPGMA) dendrogram indicated that all accessions could be divided into Oriental and Occidental groups. In Oriental pears, wild pea pears clustered separately into independent groups in accordance with their morphological classifications. Cultivars of P. ussuriensis Maxim, P. pyrifolia Nakai, and P. pyrifolia Chinese white pear were mingled together, which inferred that hybridization events occurred during the development of the cultivated Asian pears. In Occidental pears, two clades were obtained in the UPGMA dendrogram in accordance with their geographical distribution; one contained the European species and the other included species from North Africa and West Asia. New findings in this study will be important to further understand the phylogeny of Pyrus and origins of cultivated pears.

Plant hormones play a significant role in regulating growth and development during the entire life of a plant, and in response to biotic and abiotic stress. The determination of the concentrations of hormones in flowers and fruit is essential to understanding the role of hormones in the regulation of physiological and biochemical processes associated with flowering and fruit development. Based on high-performance liquid chromatography, coupled with tandem mass spectrometry, we developed and established a novel method to quantify four distinct endogenous hormones through ultra-performance liquid chromatography-tandem mass spectrometry (UPLC/ESI-MS/MS), which achieves higher throughput screening and improved resolution than HPLC or HPLC/ESI-MS/MS. Crude plant extracts were prepared by extraction with extraction solvents I and II, then purified with a Sep-Pak™ C18 reverse-phase extraction cartridge, and subsequently the purified extracts were analyzed by UPLC/ESI-MS/MS. Plant hormones, comprising indole-3-acetic acid, abscisic acid, gibberellin A4, and trans-zeatin riboside, were separated and quantified in 6 min. The method was simple, rapid, and precise, and was applied for the determination of plant hormones in pear tissue, with recoveries ranging from 70.11% to 89.84% and relative standard deviations ranging from 4.25% to 14.96%. In conclusion, sample preparation, extraction, purification, and UPLC/ESI-MS/MS conditions were optimized for quantitative analysis of four major plant hormones in pear tissue.

The effects of UV-B/VIS on the expression of genes involved in anthocyanin biosynthesis in the red Chinese sand pear cultivar ‘Mantianhong’, and the role played by the plant hormone methyl jasmonate (MJ) in this effect, were investigated. Four full-length cDNAs and three partial cDNA fragments of genes involved in anthocyanin biosynthesis were isolated from the cultivar. PpPAL2 and PpCHS2 showed considerable sequence identity to the reported PpPAL1 and PpCHS1 sequences. Other genes showed low pronounced sequence identity to other reported members of the same gene family. Bagged mature pear fruits were harvested and then used for postharvest treatment. Fruits were immersed in distilled water, then irradiated with UV-B/VIS light; or treated with MJ first, and then irradiated with UV-B/VIS light. Fruits immersed in distilled water and kept in darkness were used as controls. During UV-B/VIS irradiation, most anthocyanin biosynthesis genes were upregulated in pears in quantities commensurate with the accumulation of anthocyanin, but PpDFR1, PpDFR2, PpbHLH, and PpWD40 were not. MJ treatment had two effects on the expression of genes related to anthocyanin biosynthesis. It advanced the peak time and increased mRNA levels. Each family member of genes involved in anthocyanin biosynthesis showed a differential expression profile. The expression patterns of two genes regulating MJ-mediated plant responses, PpJAZ1 and PpCOI1, were also analyzed. More obvious downregulation and upregulation of PpJAZ1 and PpCOI1, respectively, were detected at 2 days of irradiation (DI) in fruits that were subjected to MJ treatment, as the expressions of most genes related to anthocyanin biosynthesis peaked at this time. We also showed that the regulation of MJ and UV-B/VIS occurred at the transcriptional level. These findings should improve our understanding of the molecular mechanism(s) underlying anthocyanin biosynthesis, which may in turn facilitate the development of new methods to improve fruit color.

Pyrus pashia, described as an intermediate species between oriental and occidental pear groups, is one of the most important wild pears. This study used microsatellite markers at 14 loci to assay genetic diversity and differentiation within P. pashia using three complementary methods. Four hundred and seventy seedlings were obtained from 38 half-sib families from four sites in the central Yunnan Province of China. These 14 loci displayed high polymorphism, and the descriptive statistics of diversity varied significantly among seedling populations. One hundred and seventy-three different alleles were detected, with an average of 12.4 alleles per locus. The overall expected and observed heterozygosity values were 0.749 and 0.643, respectively. Allelic richness at the different sites ranged from 1.00 to 20.36, and the Shannon’s information index for each locus was from 0.35 to 2.37, with a mean value of 1.82. Genetic differentiation was detected at both family and site levels using Bayesian model and neighbor-joining clustering approaches and the results compared with that of principal coordinate analysis. Two clusters, each with a similar number of families, were detected in the data set. Analysis of molecular variation indicated that the major variation occurred within families and that the minimum partitions of genetic variation exist among families, representing 89.14 and 10.86 % of the total variety, respectively. Families derived from site 2 displayed the maximum allelic richness and had a greatly mixed genetic composition. We recommend that these, especially families 9, 11, and 12, should be the focus of future preservation and usage investigations.

A total of 8375 genic simple sequence repeat (SSR) loci were discovered from a unigene set assembled from 116 282 transcriptomic unigenes in this study. Dinucleotide repeat motifs were the most common with a frequency of 65.11%, followed by trinucleotide (32.81%). A total of 4100 primer pairs were designed from the SSR loci. Of these, 343 primer pairs (repeat length ≥15 bp) were synthesized with an M13 tail and tested for stable amplification and polymorphism in four Pyrus accessions. After the preliminary test, 104 polymorphic genic SSR markers were developed; dinucleotide and trinucleotide repeats represented 97.11% (101) of these. Twenty-eight polymorphic genic SSR markers were selected randomly to further validate genetic diversity among 28 Pyrus accessions. These markers displayed a high level of polymorphism. The number of alleles at these SSR loci ranged from 2 to 17, with a mean of 9.43 alleles per locus, and the polymorphism information content (PIC) values ranged from 0.26 to 0.91. The UPGMA (unweighted pair-group method with arithmetic average) cluster analysis grouped the 28 Pyrus accessions into two groups: Oriental pears and Occidental pears, which are congruent to the traditional taxonomy, demonstrating their effectiveness in analyzing Pyrus phylogenetic relationships, enriching rare Pyrus EST-SSR resources, and confirming the potential value of a pear transcriptome database for the development of new SSR markers.基于转录组数据开发具有扩增率高和跨物种转移性的基因组编码区内的 SSR(genic-SSR)标记, 为梨属植物的分子系统发育关系和遗传多样性相关研究提供新的方法。首次利用梨属植物的转录组测序(RNA-seq)数据结合 M-13 荧光尾巴高效率地开发了 104 个 genic-SSR 标记, 并成功将其应用于梨属植物的系统发育关系研究中。应用生物信息学软件从转录组测序数据中搜索 SSR 位点和设计相应引物, 结合高效的 M-13 荧光尾巴的方法筛选多态性高的 SSR 标记。转录组数据能够为梨属植物分子系统发育关系和遗传多样性研究提供新的 SSR 标记来源。

In this study, we investigated two chloroplast intergenic spacers (accD-psaI and trnL-trnF) for a total of 266 individuals over 22 populations of Pyrus pashia to detect the genetic diversity, genetic, and phylogeographic structure and provide needed information for the development of conservation strategies. Thirteen haplotypes (H1–H13) were recognized. A high level of total diversity was detected (HT = 0.746). Analysis of molecular variance indicated that the genetic variation mainly existed within populations, representing 59.61 % of the total variation. Genetic differentiation among populations was high (Fst = 0.404). A Mantel test did not show a correlation between the genetic and geographic distances (r = 0.139, P = 0.09, 1,000 permutations), implying that geographic distance was not critical to gene flow among populations. A significantly higher Nst than Gst (Nst = 0.420, Gst = 0.402, P < 0.05) reflected the phylogeographic structure in P. pashia. While nested clade analyses of clade 2-2 showed that restricted gene flow existed among populations, clades 1-2 and 2-1, and the total cladogram exhibited contiguous range expansion events in P. pashia. Both sum of square deviations and the raggedness index failed to reject the sudden demographic expansion model. The overall population expansion of P. pashia was estimated to occur between 621,000 and 209,000 years ago.

Plants encounter a variety of stresses in natural environments. One-year-old pot-grown trees of pear (Pyrus pyrifolia Nakai cv. Cuiguan and Wonhwang) were exposed to two heat stress regimes. Under constant short-term heat stress, chloroplasts and mitochondria were visibly damaged. Relative chlorophyll content and maximum photochemical efficiency of photosystem II were significantly decreased, which indicated that the leaf photosynthetic capability declined. Under chronic heat stress, mesophyll cell ultrastructure was not obviously damaged, but leaf photosynthetic capability was still restrained. As chronic heat stress was a simulation of the natural environment in summer, further study of the responses under this stress regime was undertaken. Ascorbate peroxidase (APX) activity was increased in ‘Cuiguan’, but not in ‘Wonhwang’. Inducible expression of PpAPX genes in the cytoplasm, chloroplasts and peroxisomes was consistent with increased APX activity in ‘Cuiguan’, whereas only weak induction of PpAPX genes was observed in ‘Wonhwang’. The isoenzymes cytosolic APX1 (cAPX1) and stromal APX (sAPX) were confirmed to be localized in the cytoplasm and chloroplasts, respectively.

Evergreen azaleas are among the most important ornamental shrubs in China. Today, there are probably over 300 cultivars preserved in different nurseries, but with little information available on the cultivar itself or relationships between cultivars. Amplified fragment length polymorphism (AFLP) markers were employed to determine the genetic relationships between evergreen azalea cultivars in China. One hundred and thirty genotypes collected from gardens and nurseries, including cultivars classified in the groups East, West, Hairy, and Summer, unknown cultivars, and close species, were analyzed using three primer pairs. A total of 408 polymorphic fragments were generated by AFLP reactions with an average of 136 fragments per primer pair. The average values of expected heterozygosity and Shannon’s information index were 0.3395 and 0.5153, respectively. Genetic similarities were generated based on Dice coefficients, used to construct a neighbor joining tree, and bootstrapped for 100 replicates in Treecon V1.3b. Principal coordinate analysis (PCO) was performed based on Dice distances using NTSYS-pc software. The AFLP technique was useful for analyzing genetic diversity in evergreen azaleas. Cluster analysis revealed that cultivars in the West and Summer groups were quite distinct from other groups in the four-group classification system and that the East and Hairy groups should be redefined.

MicroRNAs (miRNAs) are a class of small non-coding RNA molecules that are endogenous regulators of gene expression. miRNAs play a crucial role in cells via degradation of target mRNAs or by inhibition of target protein translation. In the present study, 186 new potentially conserved pear miRNAs belonging to 37 families were identified. The length of mature miRNAs ranged from 19 to 24 nt, and most of the miRNAs (154 out of 186) were 21 nt in length. The length of pre-miRNAs in pear was also found to vary from 62 to 282 nt with an average of 105 ± 43 nt. The potential miRNAs belonged to 29 clusters involving 20 different miRNA families. Using these potential miRNAs, we further scoured of the pear genome and found 326 potential target genes, which included transcription factors, stress responsive genes, and the genes involved in transmembrane transport and signal transduction. Gene ontology analysis of these potential targets suggested that 47 biological processes were potentially regulated by miRNAs, including oxidation–reduction, stress response, transport, etc. KEGG pathway analysis showed that the identified miRNAs were found in 15 metabolism networks which were related to starch and sucrose metabolism, and ascorbate and aldarate metabolism, among others. Our study will help in the further understanding of the essential role of miRNAs in growth and development and stress response of pear.

A combined approach using nuclear SSRs and cpDNA non-coding regions was taken to study the genetic diversity and population structure of Pyrus calleryana in Zhejiang province of China. Fourteen nSSR makers and two cpDNA intergenic regions were used to study 77 individuals from 8 populations. AMOVA analyses indicated that the majority of the genetic diversity occurred within populations. Mantel tests showed that the genetic distance was significantly correlated with the geographic distance (nSSRs: r = 0.592, p = 0.008; cpDNA haplotype: r = 0.332, p = 0.048). STRUCTURE analyses exhibited that there were 2 gene pools among populations. All of the populations could be divided into 2 groups which correlated with geographic regions (northeast and southwest). Geographic distance was a key factor in shaping the current genetic structure of the P. calleryana. Population FY was the most suitable population to be protected under in situ conservation strategy.Highlights► All the populations were divided into 2 groups (northeast and southwest). ► Geographic distance was a key factor in shaping the current genetic structure. ► Population FY was the most diverse population. ► Population FY should be protected under in situ conservation strategy.

A total of 8117 suitable SSR-contaning ESTs were acquired by screening from a Malus EST database, among which dinudeotide SSRs were the most abundant repeat motif, within which, CT/TC followed by AG/GA were predominant. Based on the suitable sequences, we developed 147 SSR primer pairs, of which 94 pairs gave amplifications within the expected size range while 65 pairs were found to be polymorphic after a preliminary test. Eighteen primer pairs selected randomly were further used to assess genetic relationship among 20 Malus species or cultivars. As a result, these primers displayed high level of polymorphism with a mean of 6.94 alleles per locus and UPGMA cluster analysis grouped twenty Malus accessions into five groups at the similarity level of 0.6800 that were largely congruent to the traditional taxonomy. Subsequently, all of the 94 primer pairs were tested on four accessions of Pyrus to evaluate the transferability of the markers, and 40 of 72 functional SSRs produced polymorphic amplicons from which 8 SSR loci selected randomly were employed to analyze genetic diversity and relationship among a collection of Pyrus. The 8 primer pairs produced expected bands with the similar size in apples with an average of 7.375 alleles per locus. The observed heterozygosity of different loci ranged from 0.29 (MES96) to 0.83 (MES138), with a mean of 0.55 which is lower than 0.63 reported in genome-derived SSR marker analysis in Pyrus. The UPGMA dendrogram was similar to the previous results obtained by using RAPD and AFLP markers. Our results showed that these EST-SSR markers displayed reliable amplification and considerable polymorphism in both Malus and Pyrus, and will contribute to the knowledge of genetic study of Malus and genetically closed genera.

Simple sequence repeat (SSR) markers were used to assess genetic diversity and relationship of Pyrus L. cultivars native mainly to East Asia. A total of 168 putative alleles were generated from six primer-pairs (BGA35, KU10, BGT23b, NH004a, NH011b and NH015a). All the SSR markers showed a high level of genetic polymorphism with a mean of 28 putative alleles per locus and the heterozygosity of 0.63. The Dice’s similarity coefficient between cultivars ranged from 0.02 to 0.98 and Occidental pears generally had low affinities to Asian pears. Ten major groups were generated from all the accessions by UPGMA clusters analysis. Chinese sand pears consisted of four groups with Chinese white pears and Japanese pears, of which Chinese sand pears occurred in all four groups, presenting a large genetic diversity, Chinese white pears were included in three groups, and Japanese pears only fell into one group. In the dendrogram, Chinese sand pears and Chinese white pears did not form discrete group, even subgroups. Some Japanese pear cultivars had high affinities to Chinese sand pear cultivars. These findings supports the authors’ previous viewpoints of Chinese white pears as a variety or an ecotype of Chinese sand pears (P. pyrifolia var. sinensis (Lindley) Y. Teng et K. Tanabe) and the progenitor of Japanese pears coming from China. Cultivars of P. ussuriensis Maxim. were clustered together with one clone of P. hondoensis Nakai et Kikuchi, a relative species of P. ussuriensis. Cultivars of P. communis L. and other Occidental species formed three independent groups and were distant from most Asian pears, except for P. betulaefolia Bge.

The pigmentation patterns of ‘Mantianhong’ (Pyrus pyrifolia Nakai) and ‘Cascade’ (Pyrus communis L.) that develop under bagging and postharvest UV-B/visible irradiation conditions were evaluated in this study. The results showed that, unlike ‘Cascade,’ in which almost no anthocyanin was detected, ‘Mantianhong’ developed good red coloration under bagging treatment and postharvest irradiation. The activity of PAL and DFR increased during anthocyanin accumulation. The expression of PpCHS3, PpCHI3, PpUFGT1, and PyMYB10 was up-regulated in ‘Mantianhong’ but not in ‘Cascade’ during both treatments. This suggests that these four genes may be limiting factors for peel coloration in ‘Cascade.’ The expression patterns of gene family members were also different during fruit red coloration, suggesting that different gene family members may have distinct functions during pear development. The results obtained in this study are helpful in understanding the molecular mechanism of anthocyanin accumulation in red pears and can serve as the basis for the development of marker-assisted selection or for anthocyanin metabolic engineering of pears.Highlights► Two treatments enhanced anthocyanin content in ‘Mantianhong’ (Pyruspyrifolia). ► Two treatments scarcely promotedanthocyanin synthesisin ‘Cascade’ (P.communis). ► Expression of PpCHS3, PpCHI3, PpUFGT1, and PyMYB10 wasup-regulated in ‘Mantianhong’. ► Expression of genes was different among family members during two treatments.

A total of 100 Pyrus L. accessions native mainly to East Asia were subjected to amplified fragment length polymorphism (AFLP) analysis to evaluate genetic variability and relationships among the accessions. Six AFLP primer combinations produced a total of 459 fragments, of which 410 were polymorphic with a polymorphism percentage of 89%. The Dice's similarity coefficient among pear accessions ranged from 0.671 (P. betulaefolia Bge and P. elaeagrifolia Pall.) to 0.947 (‘Umajirou’ and ‘Immuraaki’). Occidental pears generally had low similarities to Asian pears. The dendrogram generated from all the accessions by unweighted pair-group method of arithmetic analysis (UPGMA) cluster analysis clearly distinguished Occidental pears from accessions of East Asia. P. ussuriensis Maxim., P. betulaefolia and P. communis L. clustered separately into independent groups in accordance with their morphological classification. Japanese pear cultivars formed two groups with some Chinese white pears and Chinese sand pears. Chinese white pears and Chinese sand pears independently formed their own groups and also mingled into mixed groups in the dendrogram. Therefore, Chinese white pears were treated as a cultivated group or an ecotype of P. pyrifolia: P. pyrifolia White Pear Group. The information obtained from this study will be of great help for understanding the origin and evolution of Asian pear cultivars.

Red Chinese sand pears (Pyrus pyrifolia Nakai) are particular to China. In order to determine the effects of fruit bagging treatments (including bag types, bag removal patterns and dates) on fruit qualities and to understand the mechanism of coloring of red Chinese sand pears, two experiments were carried out. In the first experiment, fruit of ‘Meirensu’ were firstly covered by light-impermeable paper bags with different levels of light permeable liners during their early development stage, then, the whole bag were/not removed or only the outer layer of bags were removed 3, 2 or 1 weeks before harvest. Thus, the fruit were/not totally re-exposed or were under different levels of sunlight transmission (80.31% or 34.71%). Non-bagged fruit were used as the control. Bagging treatments significantly affected the concentration of anthocyanin and the visual qualities of pear fruit. Compared to control, fruit re-exposed totally for 2 or 3 weeks accumulated the largest amount of anthocyanin and fruit receiving 80.31% and 34.71% of sunlight for 1–3 weeks could synthesize a little anthocyanin, indicating that high light intensity is imperative for coloring in red Chinese sand pears. Bagging treatments did not affect contents of total soluble sugars, but decreased organic acids contents in fruit. In the second experiment, fruit of ‘Meirensu’ and ‘Yunhongli No. 1’ were covered with only one type of light-impermeable bag during the early development stage and totally re-exposed after the bag removal 15 days before harvest. Fruit were then collected at different intervals to trace the time-course of coloring, and related physiology and inner qualities. With increasing time after the bag removal, the concentration of chlorophyll, carotenoid, flavonoid and total phenols changed little, but the concentration of anthocyanin accumulated extremely fast within 10 days after the bag removal in both cultivars and thereafter kept constant. ‘Yunhongli No. 1’ had higher anthocyanin contents and lower hue angle than ‘Meirensu’, indicating a higher potential of anthocyanin synthesis. After the bag removal, the sucrose contents and PAL activities increased gradually and correlation analysis revealed that they were highly correlated with anthocyanin accumulation in two cultivars. This study suggests that anthocyanin biosynthesis in red Chinese sand pears is a highly light dependent process and modified by genotypes. Based on the current results, in order to obtain red Chinese sand pear fruit with attractive appearance and good inner qualities, fruit must be covered with light-impermeable bags at the early stage of fruit development and the bag should be removed totally at least 10 days before harvest.

Recently, red Chinese sand pears (Pyrus pyrifolia Nakai) have become widely cultivated throughout China. To clarify the molecular mechanism underlying anthocyanin accumulation in red Chinese sand pears, genes encoding the anthocyanin biosynthesis enzymes including phenylalanine ammonia-lyase (PAL), chalcone synthase (CHS), chalcone isomerase (CHI), flavanone 3-hydroxylase (F3H), dihydroflavonol 4-reductase (DFR), anthocyanidin synthase (ANS) and UDP-glucose: flavonoid 3-O-glucosyltransferase (UFGT) were isolated from the mature fruit of ‘Meirensu’ pears and were designated as PpPAL, PpCHI, PpCHS, PpDFR, PpF3H, PpANS and PpUFGT, respectively. The expression of PyMYB10 and all seven anthocyanin biosynthetic genes were detected in two red pear cultivars under fruit bagging treatments during fruit maturation. The transcription level of all these genes was markedly up-regulated in two cultivars and peaked at 1 DABR (days after the bag removal) followed by a decline. All seven anthocyanin biosynthetic genes were differentially expressed among various organs or tissues, and none was fruit specific. Higher mRNA abundance of all seven anthocyanin biosynthetic genes and PyMYB10 was detected in the skin of sun-side ‘Yunhongli No. 1’ than in ‘Meirensu’ in all surveys, and in the skin of sunlit side of ‘Meirensu’ (M) than in the skin of the shaded side of ‘Meirensu’ which positively correlated with anthocyanin accumulation. Our results suggest that (1) anthocyanin accumulation in fruit of red Chinese sand pears was closely related to the coordinated expression of PyMYB10 and multiple biosynthetic genes and the level was modified by the genetic background of cultivars, and (2) light exposure after bag removal enhanced anthocyanin accumulation by inducing the expression of PyMYB10 and the anthocyanin biosynthetic genes. The results obtained in this study will be helpful in understanding the molecular mechanism of anthocyanin accumulation in red Chinese sand pears and can serve as the basis for the development of marker-assisted selection or for anthocyanin metabolic engineering of pears.Highlights► Seven anthocyanin biosynthesis genes were isolated from fruit skin of Red Chinese sand pear. ► None of the anthocyanin biosynthesis genes was fruit-specific. ► Anthocyanin accumulation in pear fruit was closely related to the expression of the gene and was determined by the genetic background. ► Light exposure after bag removal enhanced anthocyanin accumulation by inducing the expression of the anthocyanin biosynthesis genes. ► The transcript level of these genes in the sunlit side of fruit was evidently higher than this in the shaded side of fruit.

Red Chinese sand pears (Pyrus pyrifolia Nakai) have seen increased cultivation in China in recent years, prized for their attractive market value and nutritional benefits. However, poor fruit coloration has been a noticeable problem. Postharvest ultraviolet-B (UV-B)/visible irradiation has been used to improve anthocyanin accumulation and thus the coloration of fruit skin in apple and other fruits. In this study, the efficacy of UV-B/visible irradiation was evaluated under high- (27 °C) and low-temperature (17 °C) conditions using red Chinese sand pear ‘Yunhongli No. 1’ as a model. The results showed that UV-B/visible irradiation was more effective in inducing anthocyanin synthesis in peel tissues and improving fruit coloration at 27 °C than at 17 °C. PAL activity was markedly higher at 27 °C than at 17 °C. Expression of PyMYB10 and five anthocyanin structural genes, PpPAL, PpCHI, PpCHS, PpF3H, and PpANS, was also higher in fruit irradiated at 27 °C than in fruit irradiated at 17 °C. For PpUFGT, transcription reached a maximum at 48 and 240 h after the onset of irratiation at 27 °C and 17 °C, respectively, but the peak value was lower at 27 °C than at 17 °C. There was no difference in expression of PpDFR between 17 °C and 27 °C irradiation temperatures. These results indicated that high temperatures (27 °C) enhanced UV-B/visible irradiation induced postharvest anthocyanin accumulation in ‘Yunhongli No. 1’ pears by up-regulating PyMYB10 and anthocyanin structural genes and increasing the activity of phenylalanine ammonia-lyase.Highlights► Postharvest UV-B/visible irradiation induced anthocyanin accumulation in Chinese sand pear peels. ► Postharvest UV-B/visible irradiation induced red color development in Chinese sand pears. ► UV-B/visible applied at high temperature was more effective on red coloration in Chinese sand pears. ► UV-B/visible treatment up-regulated PyMYB10 gene expression. ► UV-B/visible treatment up-regulated expression of anthocyanin structural genes.

Plant hormones play a significant role in regulating growth and development during the entire life of a plant, and in response to biotic and abiotic stress. The determination of the concentrations of hormones in flowers and fruit is essential to understanding the role of hormones in the regulation of physiological and biochemical processes associated with flowering and fruit development. Based on high-performance liquid chromatography, coupled with tandem mass spectrometry, we developed and established a novel method to quantify four distinct endogenous hormones through ultra-performance liquid chromatography-tandem mass spectrometry (UPLC/ESI-MS/MS), which achieves higher throughput screening and improved resolution than HPLC or HPLC/ESI-MS/MS. Crude plant extracts were prepared by extraction with extraction solvents I and II, then purified with a Sep-Pak™ C18 reverse-phase extraction cartridge, and subsequently the purified extracts were analyzed by UPLC/ESI-MS/MS. Plant hormones, comprising indole-3-acetic acid, abscisic acid, gibberellin A4, and trans-zeatin riboside, were separated and quantified in 6 min. The method was simple, rapid, and precise, and was applied for the determination of plant hormones in pear tissue, with recoveries ranging from 70.11% to 89.84% and relative standard deviations ranging from 4.25% to 14.96%. In conclusion, sample preparation, extraction, purification, and UPLC/ESI-MS/MS conditions were optimized for quantitative analysis of four major plant hormones in pear tissue.