Genome-wide identification of the CONSTANS-LIKE(COL)family and mechanism of fruit senescence regulation by PpCOL8 in sand pear(Pyrus pyrifolia)

Pyrus pyrifolia Nakai‘Whangkeumbae'is a sand pear fruit with excellent nutritional quality and taste.However,the industrial development of pear fruit is significantly limited by its short shelf life.Salicylic acid(SA),a well-known phytohormone,can delay fruit senescence and improve shelf life.However,the mechanism by which SA regulates CONSTANS-LIKE genes(COLs)during fruit senescence and the role of COL genes in mediating fruit senescence in sand pear are poorly understood.In this study,22 COL genes were identified in sand pear,including four COLs(Pp COL8,Pp COL9a,Pp COL9b,and Pp COL14)identified via transcriptome analysis and 18 COLs through genome-wide analysis.These COL genes were divided into three subgroups according to the structural domains of the COL protein.Pp COL8,with two B-box motifs and one CCT domain,belonged to the first subgroup.In contrast,the other three Pp COLs,Pp COL9a,Pp COL9b,and Pp COL14,with similar conserved protein domains and gene structures,were assigned to the third subgroup.The four COLs showed different expression patterns in pear tissues and were preferentially expressed at the early stage of fruit development.Moreover,the expression of Pp COL8 was inhibited by exogenous SA treatment,while SA up-regulated the expression of Pp COL9a and Pp COL9b.Interestingly,Pp COL8 interacts with Pp MADS,a MADS-box protein preferentially expressed in fruit,and SA up-regulated its expression.While the production of ethylene and the content of malondialdehyde(MDA)were increased in Pp COL8-overexpression sand pear fruit,the antioxidant enzyme(POD and SOD)activity and the expression of Pp POD1 and Pp SOD1 in the sand pear fruits were down-regulated,which showed that Pp COL8 promoted sand pear fruit senescence.In contrast,the corresponding changes were the opposite in Pp MADS-overexpression sand pear fruits,suggesting that Pp MADS delayed sand pear fruit senescence.The co-transformation of Pp COL8 and Pp MADS also delayed sand pear fruit senescence.The results of this study revealed that Pp COL8 can play a key role in pear fruit senescence by interacting with Pp MADS through the SA signaling pathway.

Insights into the dwarfing mechanism of pear(Pyrus betulaefolia) based on anatomical and structural analysis using X-ray scanning

The lack of a suitable rootstock to control scion growth has limited the development of high-density plantations in pear production, which is partly attributed to poor understanding of the dwarfing mechanism. In the present study, the rootstock of the dwarf-type pear (Pyrus betulaefolia)PY-9’ was identified and used as the material for anatomical analysis.PY-9’ grew to half the tree height of the normal cultivar Zhengdu’, along with fewer internodes and shorter length. Significant differences in growth rate betweenPY-9’ andZhengdu’ were detected at approximately 30 days after full bloom, which corresponded with the time of the greatest difference in water potential between the dwarf and normal cultivar.PY-9’ showed a higher photosynthetic rate thanZhengdu’. Anatomical analysis showed thatPY-9’ had higher area ratios of both phloem and xylem and more developed vascular tissues thanZhengdu’. The three-dimensional reconstructed skeleton of the xylem from X-ray computed tomography scanning revealed greater intervessel connectivity inZhengdu’ than inPY-9’, which could contribute to the more vigorous growth ofZhengdu’. This study thus provides the first comparison of the microstructural properties of xylem elements between a dwarfing-type and vigorous-type pear rootstock, providing new insights into the dwarfing mechanism in pear and facilitating breeding of dwarf pear rootstocks to increase crop productivity.

Identification of Self-Incompatibility Genotypes in Some Sand Pears (Pyrus pyrifolia Nakai) by PCR-RFLP Analysis

The identification of self-incompatibility genotype （S-genotype） will be useful for selection of pollinizers and design of crossing in cultivar improvement of sand pear. This paper reported the identification of self-incompatibility genotypes of seven Chinese and two Japanese sand pear cultivars using PCR-RFLP analysis and S-RNase sequencing. The Sgenotypes of these cultivars were determined as follows： Huali 1 S1S3, Shounan S1S3, Xizilti S1S4, Qingxiang S3S7, Sanhua S2S7, Huangmi （Imamuranatsu） S1S6, Huali 2 S3S4, Baozhuli S7S33, Cangxixueli S5S15. S-RNase alleles （S1 to S9） in sand pear could be identified effectively by PCR-RFLP analysis.

Isolation and Characterization of a Cinnamoyl CoA Reductase Gene(CCR) in Pear(Pyrus pyrifolia)

Pear is a popular and commercially important fresh fruit, and its texture is related to the presence of sclereid formatted by parenchyma cell with lignification in vascular plants. Previous studies have demonstrated that content of lignin may be regulated by cinnamoyl CoA reductase(CCR) in various plants. However, the function of CCR in pears remains very limited. In the present study, we isolated a cDNA encoding CCR(PpCCR, GenBank accession No. KF999958) and its promoter(proPpCCR) from Whangkeumbae pear to investigate the function of CCR in lignin biosynthesis. PpCCR-GFP expressed in rice mesophyll protoplast demonstrated that PpCCR-GFP was localized in the cytoplasm, indicating that CCR may function in cytoplasm without localization signals. In transgenic plants carrying PpCCR, we observed higher lignin content compared with that in wild type plants, further suggesting that PpCCR can affect the lignin contents through regulating lignin biosynthesis in Arabidopsis thaliana. More studies in other plants are needed to confirm our conclusion.

An assessment of the genetic diversity of pear(Pyrus L.)germplasm resources based on the fruit phenotypic traits

Germplasm resources are an important basis for genetic breeding and analysis of complex traits,and research on genetic diversity is conducive to the exploration and creation of new types of germplasm.In this study,the distribution frequency,coefficient of variation,Shannon-Wiener index,and variance and cluster analyses were used to analyze the diversity and trait differences of 39 fruit phenotypic traits from 570 pear accessions,which included 456 pear accessions from 11 species and 114 interspecific hybrid cultivars that had been stored in the National Germplasm Repository of Apple and Pear(Xingcheng,China).The comprehensive evaluation indices were screened by correlation,principal component and regression analyses.A total of 132 variant types were detected in 28 categorical traits of pear germplasm fruit,which indicate a rich diversity.The diversity indices in decreasing order were:fruit shape(1.949),attitude of calyx(1.908),flesh texture type(1.700),persistency of calyx(1.681),russet location(1.658),relief of area around eye basin(1.644),flavor(1.610)and ground color(1.592).The coefficient of variation of titratable acidity in the 11 numerical traits of pear germplasm fruit was as high as 128.43%,which could more effectively reflect the differences between pear accessions.The phenotypic differentiation coefficient V_(st)(66.4%)among the five cultivated pear species,including Pyrus bretschneideri(White Pear),P.pyrifolia(Sand Pear),P.ussuriensis(Ussurian Pear),P.sinkiangensis(Xinjiang Pear),and P.communis(European Pear),was higher than the within population phenotypic differentiation coefficient V_(st)(33.6%).The variation among populations was the main source of variation in pear fruit traits.A hierarchical cluster analysis divided the 389 accessions of six cultivated pear species,including P.pashia(Himalayan Pear),into six categories.There were certain characteristics within the populations,and the differences between populations were not completely clustered by region.For example,Sand Pear cultivars from Japan and the Korean Peninsula clustered together with those from China.Most of the White Pear cultivars clustered with the Sand Pear,and a few clustered with the Ussurian Pear cultivars.The Ussurian Pear and European Pear cultivars clustered separately.The Xinjiang Pear and Himalayan Pear did not cluster together,and neither did the cultivars.Seventeen traits,three describing fruit weight and edible rate(fruit diameter,fruit length and fruit core size),five describing outer quality and morphological characteristics(over color,amount of russeting,dot obviousness,fruit shape,and stalk length),and nine describing inner quality(flesh color,juiciness of flesh,aroma,flavor,flesh texture,flesh texture type,soluble solid contents,titratable acidity,and eating quality)were selected from the 39 traits by principal component and stepwise regression analyses.These 17 traits could reflect 99.3%of the total variation and can be used as a comprehensive evaluation index for pear germplasm resources.

The Variation of Stone Cell Content in 236 Germplasms of Sand Pear(Pyrus pyrifolia)and Identification of Related Candidate Genes

Stone cells have been described to substantially influence pear fruit quality,as lignin and cellulose are the main components of stone cells.However,there are limited studies on the relationship between the variation and molecular basis of stone cells,lignin and cellulose content among different pear varieties.Here,to reveal the variation of stone cell content within different cultivated species,we collected 236 germplasms of sand pear(Pyrus pyrifolia)at 50 days after flower blooming(DAFB),the key stage of stone cell formation.In our results,we measured the content of stone cells,lignin and cellulose and found that these contents ranged from2.82%to 29.00%,8.84%to 55.30%and 11.52%to 30.55%,respectively.Further analysis showed that the variation coefficient of stone cell,lignin and cellulose content was 39.10%,28.03%and 16.71%,respectively.Additionally,a significant correlation between stone cell,lignin and cellulose content were detected,and the correlation coefficient between the contents of stone cell and lignin(0.912)was higher than between the contents of stone cell and cellulose(0.796).Moreover,the average lignin content(29.73%)was higher than the average cellulose content(18.03%)in stone cells in pear fruits,indicating that lignin is the main component of stone cell in pears.Finally,on the basic of the transcriptome data,we identified 10 transcription factors belonging to bHLH,ERF,MYB,and NAC transcript families,which might be involved in lignin formation in stone cells.qRT-PCR experiments verified coincident trends between expression of candidate genes and stone cell content.This research laid foundation for future studies on genetic variation of stone cells in pear fruits and provided important gene resources for stone cell regulation.

Transcriptional profiles underlying the effects of salicylic acid on fruit ripening and senescence in pear(Pyrus pyrifolia Nakai)

Salicylic acid(SA) plays a pivotal role in delaying fruit ripening and senescence. However, little is known about its underlying mechanism of action. In this study, RNA sequencing was conducted to analyze and compare the transcriptome profiles of SA-treated and control pear fruits. We found a total of 159 and 419 genes differentially expressed between the SA-treated and control pear fruits after 12 and 24 h of treatment, respectively. Among these differentially expressed genes(DEGs), 125 genes were continuously differentially expressed at both treatment times, and they were identified as candidate genes that might be associated with SA-regulated fruit ripening and senescence. Bioinformatics analysis results showed that 125 DEGs were mainly associated with plant hormone biosynthesis and metabolism, cell wall metabolism and modification, antioxidant systems, and senescence-associated transcription factors. Additionally, the expression of several candidate DEGs in ripening and senescent pear fruits after SA treatments were further validated by quantitative real-time PCR(qRT-PCR). This study provides valuable information and enhances the understanding of the comprehensive mechanisms of SA-meditated pear fruit ripening and senescence.

Genome-wide identification and characterization of the PbrATG family in Pyrus bretschneideri and functional analysis of PbrATG1a in response to Botryosphaeria dothidea

The pear is an economic fruit that is widely planted around the world and is loved by people for its rich nutritional value. Autophagy is a self-protection mechanism in eukaryotes, and its occurrence often accompanied by the degradation of damaged substances in cells and the recycling of nutrients. Autophagy is one of the mechanisms through which plants respond to environmental stress and plays an important role in plant development and stress resistance. Functional studies of autophagy-related genes (ATGs) have been performed on a variety of plant species, but little information is available on the ATG family in pear (Pyrus bretschneideri Rehd). Therefore, we analyzed the evolutionary dynamics and performed a genome-wide characterization of the PbrATG gene family. A total of 28 PbrATG members were identified.Phylogenetic analysis showed that PbrATGs were more closely related to ATGs of European pear and apple. Evolutionary analysis revealed that whole-genome duplication (WGD) and dispersed duplication events were the main driving forces of PbrATG family expansion.Expression analysis of different pear tissues showed that all the genes were expressed in different pear tissues, and different PbrATGs are expressed at different times and in different locations. Moreover, all PbrATGs also responded to different abiotic stresses, especially salt and drought stress, which elicited the highest expression levels. Pear seedlings were subsequently infected with Botryosphaeria dothidea (B.dothidea). The results showed that different PbrATGs had different expression patterns at different infection stages. According to the gene expression data, PbrATG1a was selected as a key autophagy gene for further analysis. Silencing of PbrATG1a reduced the resistance of pear to B. dothidea, which resulted in increased lesions, reactive oxygen species (ROS) contents, antioxidant enzyme activity, and gene expression levels in the silenced pear seedlings after B. dothidea inoculation. In this study, a comprehensive bioinformatic analysis of ATGs was conducted, and the functions of PbrATGs in pear development and in response to stress were elucidated, which laid a foundation for further study of the molecular mechanism of autophagy and a new strategy for pear resistance breeding.

Preharvest application of melatonin induces anthocyanin accumulation and related gene upregulation in red pear (Pyrus ussuriensis)

Anthocyanins are important components in the peel of red pears and contribute to the appearance of the fruit.Melatonin application is known to affect anthocyanin biosynthesis,but the effect of preharvest melatonin application on fruit coloration remains largely unknown.The objective of this study was to determine the effects of preharvest melatonin application on pigmentation,phenolic compounds,and the expression of related genes in Nanhong pear(Pyrus ussuriensis).The applications were performed during the pre-color-change period by spraying 50 or 200μmol L^(-1)of melatonin on fruits.We found that treatment with melatonin had a significant effect on color development.The concentrations of anthocyanins and flavonols were enhanced by melatonin treatment,whereas hydroxycinnamate and flavanol concentrations were reduced.Quantitative real-time PCR analyses indicated that the transcription levels for most anthocyanin biosynthetic genes and anthocyanin-related transcription factors were induced by melatonin.Melatonin application also stimulated the expression of melatonin biosynthesis-related genes and consequently caused an increase in endogenous melatonin concentration.These results provide insights into melatonin-induced fruit coloration and will facilitate the application of exogenous melatonin in agriculture.

The Storability and Its Regulatory Mechanism of HuanghuaPear(Pyrus pyrifolia Nakai.)Fruit as Influencedby Postharvest Treatments

Different temperatures and PEF packing treatments were carried out on postharvest Huanghua pear fruit to investigate their effects on fruit storability and the regulatory mechanism. LOX activity, O2- content, AOS activity, ACC synthase activity, ACC content, ACC oxidase activity and ethylene production changed with peaks in the ripening fruit at 20℃ and were inhibited by cold storage, incidence of fruit woolness and fruit decay were lightened as well. Low temperature combined with PEF packing (PEF1 and PEF2) treatments could further improve the fruit storability, maintain preferable quality. There was no significant difference between PEF1 and PEF2 both during cold storage at 1℃ and shelf life at 20℃. The recommended storage period of Huanghua fruit was two months at It and could be extended one month longer with PEF packing treatments.

The PcERF5 promotes anthocyanin biosynthesis in red-fleshed pear(Pyrus communis)through both activating and interacting with PcMYB transcription factors

As there is a strong interest in red-skinned pears,the molecular mechanism of anthocyanin regulation in red-skinned pears has been widely investigated;however,little is known about the molecular mechanism of anthocyanin regulation in red-fleshed pears due to limited availability of such germplasm,primarily found in European pears(Pyrus communis).In this study,based on transcriptomic analysis in red-fleshed and white-fleshed pears,we identified an ethylene response factor(ERF)from P.communis,PcERF5,of which expression level in fruit flesh was significantly correlated with anthocyanin content.We then verified the function of PcERF5 in regulating anthocyanin accumulation by genetic transformation in both pear skin and apple calli.PcERF5 regulated anthocyanin biosynthesis by different regulatory pathways.On the one hand,PcERF5 can activate the transcription of flavonoid biosynthetic genes(PcDFR,PcANS and PcUFGT)and two key transcription factors encoding genes PcMYB10 and PcMYB114.On the other hand,PcERF5 interacted with PcMYB10 to form the ERF5-MYB10 protein complex that enhanced the transcriptional activation of PcERF5 on its target genes.Our results suggested that PcERF5 functioned as a transcriptional activator in regulating anthocyanin biosynthesis,which provides new insights into the regulatory mechanism of anthocyanin biosynthesis.This new knowledge will provide guidance for molecular breeding of red-fleshed pear.

砂梨(Pyrus pyrifolia)过敏原蛋白基因(Ppmal)的克隆与表达分析

【目的】分离和克隆梨过敏原蛋白基因Ppmal(Gen Bank登录号为KP008110),探讨其在梨果实发育过程中的功能。【方法】以砂梨品种‘翠冠’[Pyrus pyrifolia(Burm.f.)Nakai]为试材,在盛花期后30 d对植株果柄进行涂抹赤霉素处理,利用同源克隆和RACE方法克隆目的基因全长序列,并通过实时荧光定量技术和半定量技术分析该基因在梨不同组织以及梨果实发育过程中的表达变化。【结果】Ppmal的全长是906 bp,含有480 bp的开放阅读框(ORF),编码159个氨基酸,预测的蛋白质相对分子质量为17.56 k D,等电点为5.62。生物信息学分析显示该基因没有信号肽序列,没有跨膜结构域,具亲水性。与其他物种的过敏原蛋白基因核苷酸序列同源性超过75%,与苹果和西洋梨编码的氨基酸序列同源性分别高达97.48%和96.23%,进化树分析表明该基因与苹果的进化关系最近。同时,定量结果显示经过赤霉素处理后的果实中该基因的表达量随着果实的生长发育呈现先降低后升高的趋势,并且具有组织差异表达的特点,其表达量在叶片中最大,其次是嫩叶,再次是花,枝条最低。【结论】获得梨Ppmal基因全长,对该基因在砂梨品种‘翠冠’发育过程中的表达分析显示,Ppmal受到赤霉素的调控,并在砂梨果实膨大期发生上调表达。

野生秋子梨(Pyrus ussuriensis Maxim)果实性状的遗传多样性

【目的】探讨野生秋子梨果实形态、香气物质及糖酸组分的遗传变异及遗传多样性,为野生秋子梨种质资源的保护与利用提供基本资料。【方法】以迁地保存圃的35个野生秋子梨实生株系的果实为试材,以‘小香水’梨、‘京白’梨和‘南果’梨3个秋子梨栽培品种为对照,测量果实的纵径、横径、果形指数(纵径/横径)及单果重,采用静态顶空和气相色谱-质谱联用、高效液相色谱技术,定性、定量分析果实的糖酸组分和香气物质。【结果】野生秋子梨各实生株系果实大小、香气成分总含量、各类香气成分种类数及其含量、主要香气成分分离比率与具体含量、各糖酸组分的含量、总糖以及总酸含量等均存在广泛的遗传变异,变异系数均在17%以上,各株系间差异明显,表现出丰富的遗传多样性;进一步与3个栽培品种比较发现,野生秋子梨的果实纵径、横径及单果重均小于3个栽培品种,但果形指数比较接近;野生秋子梨平均每个株系检测出41种香气成分,明显高于栽培品种的平均香气种类(25种);野生秋子梨平均香气成分含量为9.44μg·g-1,显著高于3个栽培品种的平均含量(5.71μg·g-1);野生秋子梨与栽培品种相比,含有酸类和烃衍生物类2类特有化合物,含有酯类等9类111种特有成分;野生秋子梨与3个栽培品种共检测出16种特征香气,其中1-己醇和己醛等8种化合物为野生秋子梨与3个栽培品种共有的特征香气,乙酸己酯和乙酸戊酯等8种特征香气为野生秋子梨特有;35个野生秋子梨实生株系和栽培品种中几乎均能检测出果糖、葡萄糖和蔗糖等3种糖组分以及苹果酸、酒石酸和柠檬酸等6种酸组分,且均以果糖和苹果酸含量最高;野生秋子梨中酒石酸及蔗糖含量明显高于栽培品种,其他糖酸组分、总糖及总酸含量最大值均高于3个栽培品种。【结论】野生秋子梨在果实形态、糖酸组分及香气成分上存在广泛的遗传变异,参试的35个实生株系间差异明显,遗传多样性极为丰富,并且含有酸类和烃衍生物类2类特有化合物和111种特有成分,进一步挖掘利用的潜力巨大。

Adaptive responses of Acer ginnala, Pyrus ussuriensis and Prunus davidiana seedlings to soil moisture stress

One-year-old seedlings of Amur maple (Acer ginnala Maxim), Ussurian pear (Pyrus ussuriensis Maxim) and David peach (Prunus davidiana Carr) were planted in pots in greenhouse and treated with four different soil moisture contents (75.0%, 61.1%, 46.4% and 35.4%). The results showed that net photosynthesis rate (NPR), transpiration rate (TR) and stomatal conductance (Sc) of seedlings of the three species decreased with the decease of soil moisture content, and Amur maple seedlings had the greatest change in those physiological indices, followed by Ussurian pear, David peach. Amur maple and Ussurian pear seedlings also presented a decrease tendency in water use efficiency (WUE) under lower soil moisture content, whereas this was reversed for David peach. Under water stress the biomass allocation to seedling root had a significant increase for all the experimental species. As to root/shoot ratio, Amur maple seedlings had the biggest increase, while David peach had the smallest increase. The leaf plasticity of Amur maple seedlings was greater, the leaf size and total leaf area decreased significantly as the stress was intensified. No significant change of leaf size and total leaf area was found in seedlings of Ussurian pear and David peach. It was concluded that Amur maple was more tolerant to soil moisture stress in comparison with David peach and Ussurian pear.

采后黄花梨(Pyrus pyrifolia Nakai.)果实中丙二烯氧合酶的生理功能

以不同成熟时期黄花梨果实为材料 ,研究果实采后成熟衰老进程中丙二烯氧合酶 (AOS)与几个成熟衰老相关因子的关系 ,探讨AOS的生理功能。结果表明 :2 0℃下不同成熟时期果实成熟衰老进程中的AOS活性变化均为峰形曲线 ,活性峰值出现在采后 10～ 12d ,先于乙烯跃变峰 2～ 4d ;果实成熟衰老各种相关因子的变化峰值出现的先后顺序依次是 :脂氧合酶(LOX)、自由基 (O- ·2 )、AOS、ACC (1 氨基环丙烷 1 羧酸 )合成酶、ACC、ACC氧化酶 ,最后为乙烯跃变峰的出现。 1℃下贮藏果实的AOS活性、乙烯合成和其他成熟衰老相关酶活性均受到强烈抑制 ,ACC和O- ·2 含量也较低 ,果实衰老进程被显著延缓。推测AOS是乙烯合成的上游调控因子之一。

梨(Pyrus pyrifolia Nakai)和莲藕(Nelumbo nucifera Gearte)组织中多酚氧化酶特性及褐变控制

对梨（ＰｙｒｕｓｐｙｒｉｆｏｌｉａＮａｋａｉ）、莲藕（ＮｅｌｕｍｂｏｎｕｃｉｆｅｒａＧｅａｒｔｅ）组织中多酚氧化酶（ＰＯＤ）的反应速度、底物浓度、最适温度、最佳ｐＨ值等方面的特性进行了研究，并采用硫代硫酸钠、维生素Ｃ为主剂的护色剂对防止梨、莲藕加工贮运中褐变问题进行了探讨．结果表明：ＳＯ２在０．２５％，ＶＣ在０．１％浓度时，对抑制多酚氧化酶活性，防止褐变起一定作用．

梨(Pyrus communis L.)多倍体新种质表型变异多样性研究

【目的】为选育梨(Pyrus communis L.)突破性品种提供新种质。【方法】以二倍体梨品种‘丰产’及其衍生的系列多倍体无性系为研究试材,对其在试管内及移出试管外在田间生长的自根苗植株的表型变异进行了观测。【结果】多倍体植株比二倍体茎粗、节间短;四倍体的叶色比二倍体深,厚度比二倍体大;多倍体和二倍体的叶形指数差异显著,叶缘差异明显。不同倍性无性系的叶缘变异表现多样性,有全缘变异,也有锐锯齿变异。试管繁殖条件下,混倍体叶片形状不一,有大量畸形叶片产生,而二倍体、三倍体和四倍体很少观察到畸形叶片产生。移栽入田间生长后,相对于二倍体,多倍体植株的株高显著变矮、节间长显著变短、地面以上30 cm处的树干直径显著变小。混倍体对自然环境条件适应性差,没有获得在试管外正常生长的植株。【结论】相同环境条件下,梨体细胞染色体加倍衍生的多倍体植株,比二倍体对照生长慢,且株高明显矮于二倍体。

杜梨(Pyrus betulifolia Bge.)多糖提取工艺及其清除自由基活性

通过L9(33)正交试验获得杜梨(Pyrus betulaefolia Bge.)多糖最佳提取工艺。在运用紫外光谱、红外光谱及高效液相色谱等方法研究杜梨多糖(PBP)理化性质的基础上,进一步评价了PBP对羟自由基(.OH)、超氧阴离子自由基(O2-.)和1,1-二苯基-2-苦基肼(DPPH)自由基的清除活性。结果表明,在料液比为1∶15,90℃下提取5h的最优条件下,PBP提取率达到18.65%。多角激光光散射仪分析表明,PBP分子质量为392.9kD。单糖组成分析表明,PBP是由阿拉伯糖、半乳糖醛酸、鼠李糖、半乳糖和葡萄糖组成,摩尔比为49.54∶28.68∶8.81∶8.45∶4.54。PBP不仅具有清除羟自由基和超氧阴离子自由基活性,对DPPH自由基的清除活性更强。

油红梨(Pyrus ussuriensis)果实后熟过程中香气成分的变化

通过顶空固相微萃取结合气相色谱质谱联用技术分析油红梨果实后熟不同时期挥发性组分。后熟0 d、5 d及10 d时分别检测出11、26和33种挥发性成分,主要为酯类、醛类、醇类及萜类物质。各种挥发性物质在不同的后熟时期种类及绝对含量均为升高的趋势,尤其是酯类组分的增加;35种挥发性组分中共检测出7种特征香气组分,分别为己醛、E-2-己烯醛、丁酸乙酯、2-甲基丁酸乙酯、己酸乙酯、乙酸己酯和庚酸乙酯,其中具有果香型特征的2-甲基丁酸乙酯、己酸乙酯及乙酸己酯对果实香气的贡献值较大;基于挥发性组分的差异,电子鼻能够很好的将不同时期的油红梨区分开来。

苹果梨（Pyrus Pyriforia （Burm） Nakai，cv．Pingguoli）果形畸变原因的探讨

本文研究了苹果梨果实畸变的原因，结果表明：果形偏斜与座果过多在生长期中互相挤压有关。果形严重畸变则是授粉不足或种子发育与生长不良的结果。这种变化在冬果梨的研究中也获得同样结果。对座果过多的果树可用疏花疏果的方法减少座果率。