Pear genomes display significant genetic diversity and provide novel insights into the fruit quality traits differentiation

The pear(Pyrus spp.)is well known for diverse flavors,textures,and global horticultural importance.However,the genetic diversity responsible for its extensive phenotypic variations remains largely unexplored.Here,we de novo assembled and annotated the genomes of the maternal(PsbM)and paternal(PsbF)lines of the hybrid‘Yuluxiang'pear and constructed the pear pangenome of 1.15 Gb by combining these two genomes with five previously published pear genomes representing cultivated and wild germplasm.Using the constructed pangenome,we identified 21224 gene PAVs(Presence-absence variation)and 1158812 SNPs(Single Nucleotide Polymorphism)in the non-reference genome that were absent in the PsbM reference genome.Compared with SNP markers,PAV-based analysis provides additional insights into the pear population structure.In addition,some genes associated with pear fruit quality traits have differential occurrence frequencies and differential gene expression between Asian and European populations.Moreover,our analysis of the pear pangenome revealed a mutated SNP and an insertion in the promoter region of the gene PsbMGH3.1 potentially enhance sepal shedding in‘Xuehuali'which is vital for pear quality.PsbMGH3.1 may play a role in the IAA pathway,contributing to a distinct low-auxin phenotype observed in plants by heterologously overexpressing this gene.This research helps capture the genetic diversity of pear populations and provides genomic resources for accelerating breeding.

PbGIF1 promoting cell-proliferation in pear fruit is transcriptionally activated by Pb RR1

As a cell proliferation regulator involved in wide biological processes in plants,GRF-INTERACTING FACTOR(GIF)controls different tissues development.However,whether GIF participates in fruit development remains unclear.According to transcriptome data,we identified PbGIF1was highly expressed during fruit development in cytokinins induced parthenocarpy pear.In the present study,the biofunction of PbGIF1 was initially verified.Overexpression of PbGIF1 promoted fruit size of transgenic tomato.The size of flesh fruit was not affected by cell expansion but the cell proliferation was promoted by overexpressing Pb GIF1.The accelerated cell proliferation process was also observed in PbGIF1-overexpressed transgenic pear fruit calli.The transcriptional regulation of cytokinins on PbGIF1 was further confirmed by exogenous CPPU treatments in pear fruitlets.To investigate the underlying mechanism,the cytokinins-responded factor,PbRR1,was further focused on.The results of Yeast-one-hybrid assay suggested that PbRR1 can bind to the promoter sequence of PbGIF1.The transcriptional activation of PbRR1 on PbGIF1 was also confirmed by Dual-Luciferase assays.Taken together,the results showed that cytokinins control pear fruit development via the transcriptional activation of PbGIF1 by PbRR1.

Dynamic Changes of Endogenous Hormone Content in Dangshansu Pear during Fruit Development

[Objective] The aim was to clear the relationship between fruit growth and development and endogenous hormones content in the pulp of Dangshansu pear.[Method] Choosing Dangshansu pear as material,the dynamic changes of endogenous hormones in pulp during various development stages were determined by means of enzyme linked immunosorbent assay（ELISA）.[Result] The results indicated that the content of endogenous hormones like ZR,GA and IAA promoting fruit growth showed increase trend within 15 d after pollination,and higher content of ZR,GA and IAA could promote ovary development and normal fruit setting of Dangshansu pear.The content of ZR in pulp had the highest value at the beginning of the first fast growth period,and then showed decrease trend until fruit became mature.The dynamic changes of IAA and GA were similar,namely their contents were higher in the first fast growth period,and decreased with fruit development,and then increased rapidly and was up to the maximum value in the second fast growth period,corresponding with the growth dynamic of fruit.The peaks of ABA content could be found on the 15th,45th and 120th day after pollination,which corresponded with the physiological fruit dropping and maturing period of Dangshansu pear.[Conclusion] The duration of various development periods and content of endogenous hormones of Dangshansu pear were different,and fruit growth and development were closely related to the content of endogenous hormones.

First report of Athelia bombacina causing postharvest fruit rot on pear

Pear is an important fruit crop in the world. An uncharacterized disease has been observed on pear fruits during cold storage ir~ Suning, Shenzhou, Xinji and other locations in Hebei Province, China. The incidence rate of the disease has reached 10%, and sometimes up to 20%. A particular fungus was consistently isolated from the infected pear fruit and cultured. Based on its morphology, molecular characteristics, pathogenicity and ITS sequence, the fungus was identified as Athelia bombacina. To our knowledge, this is the first report of Athelia bombacina causing postharvest fruit rot on pear.

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.

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.

Cloning,localization and expression analysis of two fw2.2-like genes in small-and large-fruited pear species

Fruit size is one of the most important agronomic characters,which is mainly determined by cell number and cell size.However,our current knowledge about pear is largely unknown.Through counting of pear mesocarp cells at different stages,we found that the cell number,rather than the cell size,is responsible for the differences between small- and large-fruited cultivars.Fruit weight-2.2（fw2.2） is an important quantitative trait locus（QTL） affecting fruit weight in tomato and functions as a negative regulator in carpel cell division.To get more insights into this QTL in pear fruit development,we isolated two putative homologous fw2.2 genes,which were designated as fw2.2-like（PbFWL） genes.PbFWLs encode Cys-rich proteins with the CCXXXXCPC motif and belong to the PLAC8 superfamily.In addition,results from the subcellular localization indicated that PbFWLs were localized in the plasma membrane.The expression profile of the PbFWL genes by qRT-PCR showed they expressed higher in small-sized fruit cultivar than that in large-sized fruit cultivar during the cell division period.In summary,our data suggest that these two PbFWLs might be negatively related to the cell division in pear fruit.

Infrared Spectroscopy and Morphological Assessments on the Nutritional Value of Prickly Pear Fruit

The prickly pear fruit helps in combating viral based infections.It is used to treat diabetes and declared to possess hypoglycemic effects.There is also record of the usage of the fruit in the olden days as a remedy for diabetes,lipid disorders,inflammation,ulcers,and pharmacologic side effects.The chemical composition and nutritional values of skin,flesh and seed of prickly pear fruit were investigated and discussed on a dry weight situation.The infrared spectra as well as scanning electron microscopy(SEM)techniques were used to identify the functional groups of carbohydrates,amino acids,and protein.The infrared spectral data of all three(skin,flesh,and seeds)species were recorded and assigned to the presence of distinguish peaks that referred to the three different sugars(glucose,fructose and saccharose)and cyclic aliphatic hydrocarbons moieties.On the other hand,the SEM is a powerful tool to investigate the morphological features of the components.SEM assays were examined on the surfaces of skin,flesh and seed branches showing a small particle that tends to form clusters with different shapes compared to each other.The Energy-dispersive X-ray spectroscopy(EDX)is an analytical technique used for the elemental analysis or chemical characterization of a sample.The EDX spectral technique of the skin,flesh and seeds were confirmed the presence of different essential and useful elements such as carbon,oxygen,magnesium,calcium,potassium,sulfur,aluminum,silicon,chloride,and phosphorus.

Production and Testing of Biopesticide for Control of Postharvest Mold Infections on Fresh Fruits of Apple and Pear

The present research aimed at producing a biopesticide with proper formulation of invert emulsion (water-in-oil type) and effective strain of?Trichoderma harzianum?then, testing it against pathogens of postharvest mold infections(Botrytis cinerea?&?Penicillium expansum) on fresh fruits of apple and pear. The?proper formulation of invert emulsion (IE#3) used for biopesticide production has the following ingredients (100% w/w): soybean oil (28.50%), coconut oil (19.50%), oil-soluble emulsifier: Tween 20 (2.0%), glycerine (4.25%), water-soluble emulsifier:?dehymuls k (0.75%),?sterile distilled water (22.5%) and conidial suspension of the effective strain ofT. harzianum?“TrichoPAL1” in water (22.5%, concentration 1 ×?107?conidia/ml). Testing efficacy of the produced biopesticide has indicated a significant reduction in the disease lesion diameter of mold infections on wounded apple and pear fruits stored at?20℃?± 1℃?compared to the untreated fruits or control (reduction from up to 38.75 to about 7.50 mm, respectively, according to?the type of mold infections and fruit type). Also, the treatment with the produced biopesticide has resulted in?a long protection period from mold infections on wounded and un-wounded fresh fruits of apple and pear stored under controlled and semi-commercial conditions(up to 2.5 months according to the type of mold infections and fruit type). In conclusion, the overall results have demonstrated the effectiveness of produced biopesticide on stored fruits under controlled and semi-commercial conditions therefore,?it is recommended to test this effectiveness on marketed fruits stored under variable conditions before applying it at a large scale.

The Effect of Different Potassium Fertilizers on Fruit Flavor Quality of ‘Xinliqihao’ Pear

[Objectives] This study was conducted to investigate the effects of different types of potassium fertilizers on the flavor and quality of pear fruit.[Methods] With ‘Xinliqihao’ as a research object,such three treatments as potassium sulfate (T1),potassium nitrate (T2) and potassium chloride (T3) were set up,with no application of potassium fertilizer as control (CK).All the fertilizers were applied into soil in the growing season.[Results] The total sugar content of ‘Xinliqihao’ was significantly higher in the potassium fertilizer treatments than that of the control.The total sugar content of T 2 (the potassium sulfate treatment) was the highest,which was 34.55% higher than that of the control,sequentially followed by T3 (the potassium nitrate treatment) and T1 (the potassium chloride treatment).The contents of fructose,glucose and sucrose in the potassium sulfate treatment were all the highest,which were 15.96%,27.32% and 52.81% higher than those of the potassium chloride treatment,respectively,and 11.36%,27.75% and 20.45% higher than the potassium nitrate treatment,respectively.The total acid content of ‘Xinliqihao’ fruit treated with different types of potassium fertilizers was higher than that of the control.The total acid content of the potassium nitrate treatment was the highest,which was 103.68% higher than that of the control,sequentially followed by the potassium sulfate treatment and the potassium chloride treatment.Both the control and potassium treatments of ‘Xinliqihao’ had the highest malic acid content,and except the potassium chloride treatment with the lowest fumaric acid content,other treatments all had the lowest tartaric acid content.Different types of potassium fertilizer treatments had different effects on the organic acid content of ‘Xinliqihao’ fruit.The types and contents of volatile aroma substances in the fruit of ‘Xinliqihao’ treated with potassium fertilizers were significantly higher than the control.The aroma substances in ‘Xinliqihao’ differed among different potassium fertilizer treatments.Specifically,78 kinds of aroma substances were detected in the potassium chloride treatment,and the total content of aroma components was the highest at 746.609 ng/g in the fruit of the potassium sulfate treatment.[Conclusions] The potassium fertilizer treatments improved the flavor and quality of ‘Xinliqihao’ pear fruit,and the potassium sulfate treatment exhibited the best effects.

Effect of Different Pollination Varieties on Qingxiang Pear Fruit Quality

With Qingxiang pear as test material,we study the effect of different pollination varieties on Qingxiang pear fruit quality. The results show that Xinshiji,Xizilu,Cuiguan and Yuanhuang as the pollination varieties for Qingxiang pear can create the best comprehensive quality,and these varieties can be chosen in production as the pollination varieties for Qingxiang pear,followed by Cuilu and Xishui.

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.

Isolation,identification and artificial inoculation of Rhizoctonia solani on pear during storage

Pear is a fruit crop of worldwide importance and cold storage is an integral part of the production and distribution of pears.An uncharacterized fungal disease has been observed on‘Huangguan’pear fruit during cold storage in Hebei Province.The fungus was consistently isolated from diseased fruit by routine tissue separation method,and shown to be the causal agent according to Koch postulates.Based on its morphology,molecular characteristics,pathogenicity and ITS sequence,the fungus was identified as Rhizoctonia solani.This study recorded postharvest fruit rot caused by Rhizoctonia solani on pear fruit in China.

The HY5 transcription factor negatively regulates ethylene production by inhibiting ACS1 expression under blue light conditions in pear

Ethylene is the main factor controlling fruit ripening of pear(Pyrus ussuriensis).Ethylene production rate is negatively correlated with fruit shelf life;therefore,it is important to decrease the ethylene levels for optimal fruit storage.Here,we observed that blue light treatment could inhibit ethylene production and promote the expression of ELONGATED HYPOCOTYL 5(PuHY5),a basic leucine zipper domain(bZIP)transcription factor.The following studies showed that PuHY5 could bind to the promoter of ACC synthase 1(PuACS1),a rate-limiting enzyme in ethylene biosynthesis,and inhibit its expression.For pears in which Pu HY5 was silenced,the ethylene production and PuACS1 expression were much higher than those in the control fruit.These results demonstrated that blue light inhibited ethylene production through the induction of Pu HY5 in pear.Our finding provides a new method for prolonging fruit shelf life.

套袋对浙梨6号果实外观和内在品质的影响

【目的】研究不同套袋处理对浙梨6号果实外观和内在品质性状的影响,为改善浙梨6号综合品质、提升果品价值提供参考。【方法】以浙梨6号为试材,设置不同果袋、不同套袋方式和不同时期套袋处理,以果实不套袋为对照,测定成熟期果实的外观和内在品质的变化情况。【结果】不同果袋处理果面亮度均显著高于对照(P<0.05);套白色单层大袋果实果锈指数显著低于对照(P<0.05),可溶性固形物、可溶性总糖含量和甜度值与对照无显著差异。二次套袋果实果锈指数显著低于对照和一次套袋,可溶性固形物、可溶性总糖、可滴定酸和维生素C(Vitamin C,VC)含量与对照无显著差异,果糖、葡萄糖含量和甜度值显著高于对照和一次套袋(P<0.05)。盛花后10、20、30 d套袋,黄绿果较多(≥50%),果锈指数较低(0.471~0.600),果点直径和密度显著低于对照,而盛花后60 d套袋,全锈果较多(72.5%);除盛花后10 d处理外,各时期套袋果实可溶性固形物、可溶性总糖、可滴定酸和VC含量均与对照无显著差异。【结论】套白色单层大袋对浙梨6号果实外观品质改善效果显著,同时采用“白色小蜡袋+白色单层大袋”的二次套袋方式,盛花后10~30 d为生产黄绿色果品的防锈套袋适宜期,盛花后60 d为生产全锈褐皮果品的不防锈套袋适宜期,套袋对果实内在品质无显著负面影响。

脱萼剂对“浙梨6号”果实品质与着果率的影响

针对“浙梨6号”因部分萼片宿存或残存、果顶尖凸等而影响果实品相问题,选择PBO、氟硅唑、丙环唑3种脱萼剂,以清水为对照进行试验。结果表明:与对照相比,3种脱萼剂处理果实的脱萼率提高23.27~26.01百分点,果顶尖凸率降低24.55~26.44百分点,扁圆果占比、单果质量、可溶性固形物含量分别增加33.19~37.66百分点、37.9~57.1 g和0.68~0.94百分点,但果实偏斜度、全锈果率分别偏高0.54~0.74和18.36~19.23百分点,端正果率、着果率分别下降15.89~21.07和5.43~6.62百分点,差异达显著或极显著水平。上述3种脱萼剂分别选择4000、333.3、444.4 mg·L^(-1)和花序分离期进行喷施,在保证脱萼防凸效果的同时,可有效降低对着果率及果形端正度等的不利影响。

林芝市引进梨品种果实品质的综合分析与评价模型构建

【目的】在西藏引入不同优良梨品种,以调整区内梨果树种植结构,为推动西藏特色林果业发展提供理论依据。【方法】以西藏林芝市引入的9个梨品种作为试验材料,成熟后测定其12项果实品质指标。通过相关性分析和因子分析,建立基于因子分析、主成分分析、线性回归分析以及相似性分析的综合品质评价模型,并根据综合品质得分进行优良度排序,筛选出适宜林芝市种植的优良梨品种。【结果】9个梨品种的果实品质性状变异系数有所不同,其中果形指数的变异系数较大,单果质量、果实硬度、可滴定酸含量、固酸比和石细胞含量的变异系数均中等,果实横径、果实纵径、果心横径、果心比、可溶性固形物和维生素C含量的变异系数均相对较小。对9个梨品种的12项果实品质性状的因子分析,得知前4个公因子的累积方差贡献率达89.120%,其中,第1个公因子的贡献率为37.240%,主要反映果实大小和酸甜口感品质,第2个公因子的贡献率为20.658%,主要反映了梨果实的软硬程度,第3个公因子的贡献率为17.760%,主要反映了果实形状和维生素C含量,第4个公因子的贡献率为13.642%,主要反映了果实可食部分大小和果实糖含量。各品种间存在显著的统计差异(R=0.768,p=0.001),新梨七号与晚秋黄品种显示出最大的差异性。品种间在多维性状上的分布特点表明质量和横径被识别为分类的关键因素。经综合品质评价模型,得出9个梨品种在林芝种植后的果实综合品质得分高低排序为圆黄、华山、翠冠、中梨1号、初夏绿、新梨七号、翠玉、红太阳和晚秋黄。【结论】研究结果对指导西藏自治区内特色梨品种的选育和促进梨产业的可持续发展具有重要意义。

中国梨园全程机械化发展现状及建议

对当前梨园生产管理机械化发展情况进行分析,阐述了制约实现梨园全程机械化发展的关键生产环节是果实套袋、疏花疏果、水肥一体化、智能采收。提出全程机械化发展建议,包括制定和实行利于梨园全程机械化的标准、研发适宜化机械、建立健全果园机械化社会化服务体系。

库尔勒香梨大疆T50无人机授粉参数优选与田间验证

为了提高库尔勒香梨无人机授粉作业的精确性,选用大疆T50无人机,采用三因素(作业速度、作业高度、667 m^(2)喷施量)三水平的正交试验,比较雾滴覆盖率、雾滴密度及雾滴沉积量的分布效果,筛选作业参数并进行了田间授粉效果的验证。结果表明:在环境风速不超过1.5 m/s的条件下,大疆T50无人机对纺锤形库尔勒香梨授粉的最佳作业参数为作业速度4 m/s、作业高度距离树顶4.5 m、667 m^(2)喷施量4L;田间授粉的花序坐果率为75.56%,花朵坐果率为32.87%。影响库尔勒香梨树冠上层雾滴效果的主要因素依次为667 m^(2)喷施量、作业高度、作业速度,影响树冠中层和下层雾滴效果的主要因素依次为667 m^(2)喷施量、作业速度、作业高度。

不同包装处理对甘孜州梨果仙人掌果实运输后品质的影响

以梨果仙人掌果实为试材,在常温和低温2种条件下,分别采用水果网袋、泡沫填充物、分层隔离板、塑料保鲜膜共计8种处理对其进行物流包装,通过测定运输前后梨果仙人掌果实硬度、可溶性固形物、可滴定酸、失重率、出汁率、好果率及乙醇、葡萄糖、维生素C的含量,研究不同物流包装对梨果仙人掌果实品质的影响,以期选出适合该果实的物流包装方法。结果表明:在物流运输后,低温组各处理的梨果仙人掌果实品质均显著高于各常温组。单果用保鲜膜包装的方式比泡沫填充包装、单果网带包装及泡沫板分层包装更能维持果实的硬度,减缓维生素C、可溶性固形物、葡萄糖含量的降低及出汁率、好果率的下降,限制乙醇含量、失重率的增加。不同包装处理对梨果仙人掌果实可滴定酸含量影响不显著。综上所述,低温及单果采用保鲜膜包装的形式能很好改善物流运输中梨果仙人掌品质的裂变。