Acetonic crude extracts from raw and roasted Georgia pecans were prepared and subjected to in vitro gastrointestinal digestion.Digested and undigested extracts of raw pecan phenolics were then separated into low-and h...Acetonic crude extracts from raw and roasted Georgia pecans were prepared and subjected to in vitro gastrointestinal digestion.Digested and undigested extracts of raw pecan phenolics were then separated into low-and high-molecular-weight(LMW and HMW)fractions via Sephadex LH-20 column chromatography;afterwards,they were characterized by RP-HPLC-ESI-MS.The LMW fraction consisted primarily of flavan-3-ols and ellagic acid derivatives and following digestion there was an overall loss in phenolics from 16%to 100%.In the HMW fraction,procyanidins with degrees of polymerization ranging from dimers to hexamers were present.Following digestion,a loss in higher oligomeric procyanidins was observed,along with a significant increase in quantity of dimers.This increase was attributed to the dimerization of(+)-catechin/(-)-epicatechin and the scission of larger procyanidins,mainly tetramers to hexamers.The loss of phenolics following digestion,as seen by HPLC characterization,was reflected in reduced total phenolics content and antioxidant capacity,as determined by selected in vitro antioxidant assays.展开更多
Pecan is an extremely important crop cultivated worldwide for edible nuts and nut oil.Considering the changes in precipitation and soil moisture caused by climate change and worsening global water scarcity,it is impor...Pecan is an extremely important crop cultivated worldwide for edible nuts and nut oil.Considering the changes in precipitation and soil moisture caused by climate change and worsening global water scarcity,it is important to understand the mechanism of pecan response to drought.To this end,this study investigated the response of pecan to drought stress and rehydration using physiological and transcriptomic analyses.Superoxide dismutase(SOD)enzyme activity in leaves was significantly upregulated during drought stress,suggesting that it might play an important role in drought response.Weighted gene co-expression network analysis of the transcriptome data was used to screen for a key drought-responsive gene,CiNAC2,which was overexpressed in Arabidopsis thaliana for functional validation.The analysis of stomatal apertures and the water loss rate in leaves showed that CiNAC2 might respond to drought stress via mediating stomatal aperture size.In addition,CiNAC2 could promote root growth under drought conditions.CiSOD1 was verified as a direct target gene of CiNAC2 by yeast one-hybrid assay dual-luciferase reporter assay.Yeast one-hybrid analysis confirmed that CiNAC2 bound to the promoters of CiSOD1.Transient expression in Nicotiana benthamiana epidermis showed that CiNAC2 upregulated the expression of CiSOD1.These results demonstrated that CiNAC2 enhanced drought stress tolerance via promoting SOD activity in pecan and provided a theoretical basis for breeding drought-resistant varieties in pecan.展开更多
Budding is an important grafting technique to asexually propagate pecan(Carya illinoinensis(Wangenh.)K.Koch).To determine factors that might hamper success-ful budding of the species,a representative easy-to-survive c...Budding is an important grafting technique to asexually propagate pecan(Carya illinoinensis(Wangenh.)K.Koch).To determine factors that might hamper success-ful budding of the species,a representative easy-to-survive cultivar‘Pawnee’and a typical difficult-to-survive culti-var‘Jinhua’were used for comprehensive analysis.Mor-phological observation showed that cells surrounding the secretory cells or sieve tube had collapsed in‘Jinhua’but not in‘Pawnee’during grafting.‘Jinhua’might suffer more hypoxia stress than‘Pawnee’as‘Jinhua’had higher catalase,superoxide dismutase,polyphenol oxidase,pyruvate decar-boxylase(PDC),alcohol dehydrogenase(ADH)activities during grafting and contained greater levels of hydrogen per-oxide 12 days after grafting(DAG).Transcriptions of PDC and ADH were also up-regulated significantly in‘Jinhua’whereas they were not significantly affected in‘Pawnee’.Phenylalanine ammonia-lyase activities of‘Jinhua’were consistently lower than that of‘Pawnee’.Initial phenol con-tents were similar between the two cultivars.Graft-promot-ing substances,including soluble sugar,soluble protein,and gibberellin(GA)were incompletely recovered in‘Jinhua’12 DAG while fully restored in‘Pawnee’.Increased levels of trans-zeatin riboside in‘Jinhua’were much smaller than in‘Pawnee’3 DAG.The contents of indole-3-acetic acid were similar,and the dynamics of abscisic acid were the same between the two genotypes.Results suggest that hypoxia stress and shortages of sugar,protein,GA,and cytokinin during the healing process might be key factors limiting successful budding of pecan.The degree of scion-rootstock compatibility and the content of phenols might be excluded as constraints for successful budding.展开更多
Ammonium nitrogen(NH4+-N)is one of the main forms of nitrogen absorbed and utilized by plants,and mastering the regulatory mechanism of plant ammonium assimilation is a key way to improve the efficiency of plant nitro...Ammonium nitrogen(NH4+-N)is one of the main forms of nitrogen absorbed and utilized by plants,and mastering the regulatory mechanism of plant ammonium assimilation is a key way to improve the efficiency of plant nitrogen utilization.Glutamine synthetase(GS)and glutamate synthase(GOGAT),two key enzymes for ammonium assimilation,have rarely been studied in pecan.In this study,GS and GOGAT family members of pecan were identified and analyzed using bioinformatics methods.The results indicated that 6 GS and 4 GOGAT genes were identified.The cis-acting elements can be broadly categorized into light-responsive,hormone-responsive,and stress-responsive elements.The findings from the analysis of homologous evolution revealed that neither of the two gene families experienced tandem duplication events.Additionally,different ratios of ammonium to nitrate nitrogen were set to analyze the activities of GS and GOGAT enzymes and expression levels in pecan.The results demonstrate differences in the activities of GS and GOGAT enzymes and the gene expression levels in various tissues of pecan under different nitrogen form ratios.This study established a foundation for further mastering the molecular regulatory mechanism of nitrogen assimilation in pecan,and provided a theoretical basis for enhancing the ability of pecan to absorb and utilize nitrogen.展开更多
Euplatypus segnis is an insect pest of economic importance in pecan (Carya illinoensis) trees grown at Parras, General Cepeda and Torreón Coahuila, Mexico. The objectives in this study-were to identify the fungal...Euplatypus segnis is an insect pest of economic importance in pecan (Carya illinoensis) trees grown at Parras, General Cepeda and Torreón Coahuila, Mexico. The objectives in this study-were to identify the fungal strains associated to ambrosia borer body and diseased pecan wood and determine their pathogenicity. The results showed that the associated fungi to Euplatypus segnis and damaging the pecan wood were identified as: Helminthosporium sp., Aspergillus sp., Penicillium sp., Phoma sp., Ascochyta sp., Phaecylomices sp., Umbeliopsis sp., Torula sp., Fusarium solani, Alternaria alternata, Fusarum oxysporum, and Lasiodiplodia theobromae. The pathogenicity tests on healthy 3 year old pecan trees cv. western using Fusarium oxysporum, Fusarium solani, Alternaria alternata and Lasiodiplodia theobromae suspension conidia shown die back tree branches after 84 days inoculation. The insect in combination with the fungal invasion eventually cause the death of trees. Additionally, the insect contributes to the spread of fungi in pecan nut orchards.展开更多
The pecan nut is considered one of the most important dried fruits in the world by its classification as healthy food. The nutritional balance in the harvest is crucial for its impact on the production, quality and co...The pecan nut is considered one of the most important dried fruits in the world by its classification as healthy food. The nutritional balance in the harvest is crucial for its impact on the production, quality and content of bioactive compounds. This research was carried out in the city of Aldama, Chihuahua (Mexico), where doses of mineral and organic fertilization were tested in L25 Taguchi structure with 6 factors and 5 levels by factor: nitrogen (N) 0 - 240 kg·ha-1, phosphate (P2O5) 0 - 120 kg·ha-1, potassium (K2O) 0 - 100 kg·ha-1, calcium (CaO) 0 - 400 kg·ha-1, liquid humus 0 - 3600 L·ha-1 and solid humus 0 - 8000 kg·ha-1. An average yield of 2.2 t·ha-1 was obtained;145 nuts per kilogram, 60% of the edible part of the nut. The total phenolic content was 225.9 mg gallic acid g-1 and the antioxidant capacity was 180.9 mg Trolox g-1. It is concluded that the factor with the greatest impact on yield, quality and antioxidant capacity in pecan nut was nitrogen. It was also found that the combination of mineral and organic fertilization helps to maintain the production and quality ranges of the nut. In turn, these factors contribute to the increase in the phenolic strength and antioxidant capacity. The optimal fertilization dosis to obtain the maximum levels in production of 3.2 t·ha-1;decrease the number of nuts per kilogram to 135, increase the percentage of the edible part of the nut to 61.8%, the increase in the total phenolic content to 318.6 mg of gallic acid g-1 and in the antioxidant capacity with 187.2 mg of Trolox g-1, was 184 kg·ha-1 of N, 107.4 kg·ha-1 of P2O5, 50 kg·ha-1 of K2O y 2777 L·ha-1 of liquid humus. Finally, the mineral fertilization complemented with organic fertilization is considered a good fertilization strategy for pecan trees and its possible benefits to health and the environment.展开更多
Objectives:The changes in the chemical composition of oil from pecan kernels following infection with black spot disease were evaluated to determine whether the disease affects the quality of the seed oil.The fndings ...Objectives:The changes in the chemical composition of oil from pecan kernels following infection with black spot disease were evaluated to determine whether the disease affects the quality of the seed oil.The fndings should provide theoretical support for developing the pecan industry and enhancing the risk resistance of the industry.Materials and Methods:Oil samples from healthy and diseased pecan kernels were obtained using the squeezing method,and the bioactive substances and fatty acid composition of the two types of oil samples were compared.The degree of oxidation and deterioration of the diseased kernel oil was evaluated.Based on supervised orthogonal partial least squares-discriminant analysis,gray correlation analysis,and unsupervised factor analysis,a multivariate evaluation model was established to comprehensively score the quality of the two types of oils.Results:The results showed that,compared with the healthy kernel oil,the contents of total polyphenols and favonoids,as well as the peroxide and acid values,were signifcantly higher in the diseased kernel oil.The content of oleic acid,as well as the ratio of monounsaturated fatty acids to polyunsaturated acids,was also signifcantly higher in the diseased kernel oil.In addition,no afatoxin was detected.Multivariate analysis revealed no signifcant difference in the quality of diseased kernel oil compared with that of healthy kernel oil.Conclusions:Therefore,following infection,the pecan oil begins to oxidize,but this does not have a signifcant negative effect on the nutrients,suggesting that oil from diseased kernels has the potential to be further processed and sold as edible-grade vegetable oil.展开更多
Although the development of the robot picking vision system is widely applied,it is very challenging for fruit detection in orchards with complex light and environment,especially for fruit colors similar to the backgr...Although the development of the robot picking vision system is widely applied,it is very challenging for fruit detection in orchards with complex light and environment,especially for fruit colors similar to the background.In recent,there are few studies on pecan fruit detection and location based on machine vision.In this study,an accurate and efficient pecan fruit detection method was proposed based on machine vision under natural pecan orchards.In order to solve the illumination problem,a light compensation algorithm was first utilized to process the collected samples,and then an improved Faster Region Convolutional Neural Network(Faster RCNN)with the Feature Pyramid Networks(FPN)was established to train the samples.Finally,the pecan number counting method was introduced to count the number of pecan.A total of 241 pecan images were tested,and comparison experiments were carried out.The mean average precision(mAP)of the proposed detection method was 95.932%,compared with the result without uneven illumination correction(UIC),which was increased by 0.849%,while the mAP of the Single Shot Detector(SSD)+FPN was 92.991%.In addition,the number of clusters was counted using the proposed method with an accuracy rate of 93.539%compared with the actual clusters.The results demonstrate that the proposed network has good robustness for pecan fruit detection in different illumination and various unstructured environments,and the experimental achievement has great potential for robot-picking visual systems.展开更多
Pecan(Carya illinoinensis)is a tree nut crop of worldwide economic importance that is rich in healthpromoting factors.However,pecan production and nut quality are greatly challenged by environmental stresses such as t...Pecan(Carya illinoinensis)is a tree nut crop of worldwide economic importance that is rich in healthpromoting factors.However,pecan production and nut quality are greatly challenged by environmental stresses such as the outbreak of severe fungal diseases.Here,we report a high-quality,chromosome-scale genome assembly of the controlled-cross pecan cultivar‘Pawnee’constructed by integrating Nanopore sequencing and Hi-C technologies.Phylogenetic and evolutionary analyses reveal two whole-genome duplication(WGD)events and two paleo-subgenomes in pecan and walnut.Time estimates suggest that the recent WGD event and considerable genome rearrangements in pecan and walnut account for expansions in genome size and chromosome number after the divergence from bayberry.The two paleo-subgenomes differ in size and protein-coding gene sets.They exhibit uneven ancient gene loss,asymmetrical distribution of transposable elements(especially LTR/Copia and LTR/Gypsy),and expansions in transcription factor families(such as the extreme pecan-specific expansion in the far-red impaired response 1 family),which are likely to reflect the long evolutionary history of species in the Juglandaceae.A whole-genome scan of resequencing data from 86 pecan scab-associated core accessions identified 47 chromosome regions containing 185 putative candidate genes.Significant changes were detected in the expression of candidate genes associated with the chitin response pathway under chitin treatment in the scab-resistant and scabsusceptible cultivars‘Excell’and‘Pawnee’.These findings enable us to identify key genes that may be important susceptibility factors for fungal diseases in pecan.The high-quality sequences are valuable resources for pecan breeders and will provide a foundation for the production and quality improvement of tree nut crops.展开更多
文摘Acetonic crude extracts from raw and roasted Georgia pecans were prepared and subjected to in vitro gastrointestinal digestion.Digested and undigested extracts of raw pecan phenolics were then separated into low-and high-molecular-weight(LMW and HMW)fractions via Sephadex LH-20 column chromatography;afterwards,they were characterized by RP-HPLC-ESI-MS.The LMW fraction consisted primarily of flavan-3-ols and ellagic acid derivatives and following digestion there was an overall loss in phenolics from 16%to 100%.In the HMW fraction,procyanidins with degrees of polymerization ranging from dimers to hexamers were present.Following digestion,a loss in higher oligomeric procyanidins was observed,along with a significant increase in quantity of dimers.This increase was attributed to the dimerization of(+)-catechin/(-)-epicatechin and the scission of larger procyanidins,mainly tetramers to hexamers.The loss of phenolics following digestion,as seen by HPLC characterization,was reflected in reduced total phenolics content and antioxidant capacity,as determined by selected in vitro antioxidant assays.
基金supported by the National Key R&D Program of China(Grant No.2022YFD220040203)Jiangxi Forestry Bureau forestry Science and technology innovation special project“Introduction test and Screening of pecan clones”innovation special project[Grant No.(2020)04]。
文摘Pecan is an extremely important crop cultivated worldwide for edible nuts and nut oil.Considering the changes in precipitation and soil moisture caused by climate change and worsening global water scarcity,it is important to understand the mechanism of pecan response to drought.To this end,this study investigated the response of pecan to drought stress and rehydration using physiological and transcriptomic analyses.Superoxide dismutase(SOD)enzyme activity in leaves was significantly upregulated during drought stress,suggesting that it might play an important role in drought response.Weighted gene co-expression network analysis of the transcriptome data was used to screen for a key drought-responsive gene,CiNAC2,which was overexpressed in Arabidopsis thaliana for functional validation.The analysis of stomatal apertures and the water loss rate in leaves showed that CiNAC2 might respond to drought stress via mediating stomatal aperture size.In addition,CiNAC2 could promote root growth under drought conditions.CiSOD1 was verified as a direct target gene of CiNAC2 by yeast one-hybrid assay dual-luciferase reporter assay.Yeast one-hybrid analysis confirmed that CiNAC2 bound to the promoters of CiSOD1.Transient expression in Nicotiana benthamiana epidermis showed that CiNAC2 upregulated the expression of CiSOD1.These results demonstrated that CiNAC2 enhanced drought stress tolerance via promoting SOD activity in pecan and provided a theoretical basis for breeding drought-resistant varieties in pecan.
基金funded by the National Natural Science Foundation of China(3190134732001350)+1 种基金the Central Government Demonstration Project of Forestry Science and Technology(su[2022]TG11)the Key Research and Development Plan of Jiangxi Province(20223BBF61014).
文摘Budding is an important grafting technique to asexually propagate pecan(Carya illinoinensis(Wangenh.)K.Koch).To determine factors that might hamper success-ful budding of the species,a representative easy-to-survive cultivar‘Pawnee’and a typical difficult-to-survive culti-var‘Jinhua’were used for comprehensive analysis.Mor-phological observation showed that cells surrounding the secretory cells or sieve tube had collapsed in‘Jinhua’but not in‘Pawnee’during grafting.‘Jinhua’might suffer more hypoxia stress than‘Pawnee’as‘Jinhua’had higher catalase,superoxide dismutase,polyphenol oxidase,pyruvate decar-boxylase(PDC),alcohol dehydrogenase(ADH)activities during grafting and contained greater levels of hydrogen per-oxide 12 days after grafting(DAG).Transcriptions of PDC and ADH were also up-regulated significantly in‘Jinhua’whereas they were not significantly affected in‘Pawnee’.Phenylalanine ammonia-lyase activities of‘Jinhua’were consistently lower than that of‘Pawnee’.Initial phenol con-tents were similar between the two cultivars.Graft-promot-ing substances,including soluble sugar,soluble protein,and gibberellin(GA)were incompletely recovered in‘Jinhua’12 DAG while fully restored in‘Pawnee’.Increased levels of trans-zeatin riboside in‘Jinhua’were much smaller than in‘Pawnee’3 DAG.The contents of indole-3-acetic acid were similar,and the dynamics of abscisic acid were the same between the two genotypes.Results suggest that hypoxia stress and shortages of sugar,protein,GA,and cytokinin during the healing process might be key factors limiting successful budding of pecan.The degree of scion-rootstock compatibility and the content of phenols might be excluded as constraints for successful budding.
基金supported by Jiangsu Provincial Forestry Bureau,Central Financial Forestry Science and Technology Promotion Demonstration Fund Project(Su[2022]TG04).
文摘Ammonium nitrogen(NH4+-N)is one of the main forms of nitrogen absorbed and utilized by plants,and mastering the regulatory mechanism of plant ammonium assimilation is a key way to improve the efficiency of plant nitrogen utilization.Glutamine synthetase(GS)and glutamate synthase(GOGAT),two key enzymes for ammonium assimilation,have rarely been studied in pecan.In this study,GS and GOGAT family members of pecan were identified and analyzed using bioinformatics methods.The results indicated that 6 GS and 4 GOGAT genes were identified.The cis-acting elements can be broadly categorized into light-responsive,hormone-responsive,and stress-responsive elements.The findings from the analysis of homologous evolution revealed that neither of the two gene families experienced tandem duplication events.Additionally,different ratios of ammonium to nitrate nitrogen were set to analyze the activities of GS and GOGAT enzymes and expression levels in pecan.The results demonstrate differences in the activities of GS and GOGAT enzymes and the gene expression levels in various tissues of pecan under different nitrogen form ratios.This study established a foundation for further mastering the molecular regulatory mechanism of nitrogen assimilation in pecan,and provided a theoretical basis for enhancing the ability of pecan to absorb and utilize nitrogen.
文摘Euplatypus segnis is an insect pest of economic importance in pecan (Carya illinoensis) trees grown at Parras, General Cepeda and Torreón Coahuila, Mexico. The objectives in this study-were to identify the fungal strains associated to ambrosia borer body and diseased pecan wood and determine their pathogenicity. The results showed that the associated fungi to Euplatypus segnis and damaging the pecan wood were identified as: Helminthosporium sp., Aspergillus sp., Penicillium sp., Phoma sp., Ascochyta sp., Phaecylomices sp., Umbeliopsis sp., Torula sp., Fusarium solani, Alternaria alternata, Fusarum oxysporum, and Lasiodiplodia theobromae. The pathogenicity tests on healthy 3 year old pecan trees cv. western using Fusarium oxysporum, Fusarium solani, Alternaria alternata and Lasiodiplodia theobromae suspension conidia shown die back tree branches after 84 days inoculation. The insect in combination with the fungal invasion eventually cause the death of trees. Additionally, the insect contributes to the spread of fungi in pecan nut orchards.
文摘The pecan nut is considered one of the most important dried fruits in the world by its classification as healthy food. The nutritional balance in the harvest is crucial for its impact on the production, quality and content of bioactive compounds. This research was carried out in the city of Aldama, Chihuahua (Mexico), where doses of mineral and organic fertilization were tested in L25 Taguchi structure with 6 factors and 5 levels by factor: nitrogen (N) 0 - 240 kg·ha-1, phosphate (P2O5) 0 - 120 kg·ha-1, potassium (K2O) 0 - 100 kg·ha-1, calcium (CaO) 0 - 400 kg·ha-1, liquid humus 0 - 3600 L·ha-1 and solid humus 0 - 8000 kg·ha-1. An average yield of 2.2 t·ha-1 was obtained;145 nuts per kilogram, 60% of the edible part of the nut. The total phenolic content was 225.9 mg gallic acid g-1 and the antioxidant capacity was 180.9 mg Trolox g-1. It is concluded that the factor with the greatest impact on yield, quality and antioxidant capacity in pecan nut was nitrogen. It was also found that the combination of mineral and organic fertilization helps to maintain the production and quality ranges of the nut. In turn, these factors contribute to the increase in the phenolic strength and antioxidant capacity. The optimal fertilization dosis to obtain the maximum levels in production of 3.2 t·ha-1;decrease the number of nuts per kilogram to 135, increase the percentage of the edible part of the nut to 61.8%, the increase in the total phenolic content to 318.6 mg of gallic acid g-1 and in the antioxidant capacity with 187.2 mg of Trolox g-1, was 184 kg·ha-1 of N, 107.4 kg·ha-1 of P2O5, 50 kg·ha-1 of K2O y 2777 L·ha-1 of liquid humus. Finally, the mineral fertilization complemented with organic fertilization is considered a good fertilization strategy for pecan trees and its possible benefits to health and the environment.
文摘Objectives:The changes in the chemical composition of oil from pecan kernels following infection with black spot disease were evaluated to determine whether the disease affects the quality of the seed oil.The fndings should provide theoretical support for developing the pecan industry and enhancing the risk resistance of the industry.Materials and Methods:Oil samples from healthy and diseased pecan kernels were obtained using the squeezing method,and the bioactive substances and fatty acid composition of the two types of oil samples were compared.The degree of oxidation and deterioration of the diseased kernel oil was evaluated.Based on supervised orthogonal partial least squares-discriminant analysis,gray correlation analysis,and unsupervised factor analysis,a multivariate evaluation model was established to comprehensively score the quality of the two types of oils.Results:The results showed that,compared with the healthy kernel oil,the contents of total polyphenols and favonoids,as well as the peroxide and acid values,were signifcantly higher in the diseased kernel oil.The content of oleic acid,as well as the ratio of monounsaturated fatty acids to polyunsaturated acids,was also signifcantly higher in the diseased kernel oil.In addition,no afatoxin was detected.Multivariate analysis revealed no signifcant difference in the quality of diseased kernel oil compared with that of healthy kernel oil.Conclusions:Therefore,following infection,the pecan oil begins to oxidize,but this does not have a signifcant negative effect on the nutrients,suggesting that oil from diseased kernels has the potential to be further processed and sold as edible-grade vegetable oil.
基金funded by the Forestry Science and Technology Innovation Fund Project of Hunan Province(Grant No.XLK202108-4)and the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘Although the development of the robot picking vision system is widely applied,it is very challenging for fruit detection in orchards with complex light and environment,especially for fruit colors similar to the background.In recent,there are few studies on pecan fruit detection and location based on machine vision.In this study,an accurate and efficient pecan fruit detection method was proposed based on machine vision under natural pecan orchards.In order to solve the illumination problem,a light compensation algorithm was first utilized to process the collected samples,and then an improved Faster Region Convolutional Neural Network(Faster RCNN)with the Feature Pyramid Networks(FPN)was established to train the samples.Finally,the pecan number counting method was introduced to count the number of pecan.A total of 241 pecan images were tested,and comparison experiments were carried out.The mean average precision(mAP)of the proposed detection method was 95.932%,compared with the result without uneven illumination correction(UIC),which was increased by 0.849%,while the mAP of the Single Shot Detector(SSD)+FPN was 92.991%.In addition,the number of clusters was counted using the proposed method with an accuracy rate of 93.539%compared with the actual clusters.The results demonstrate that the proposed network has good robustness for pecan fruit detection in different illumination and various unstructured environments,and the experimental achievement has great potential for robot-picking visual systems.
基金This work was supported by grants from the Natural Science Foundation of Zhejiang Province,China(grant no.Z20C160001)the State Key Laboratory of Subtropical Silviculture at Zhejiang A&F University(grant no.ZY20180202)the Research and Development Fund of Zhejiang A&F University(grant no.2018FR002).
文摘Pecan(Carya illinoinensis)is a tree nut crop of worldwide economic importance that is rich in healthpromoting factors.However,pecan production and nut quality are greatly challenged by environmental stresses such as the outbreak of severe fungal diseases.Here,we report a high-quality,chromosome-scale genome assembly of the controlled-cross pecan cultivar‘Pawnee’constructed by integrating Nanopore sequencing and Hi-C technologies.Phylogenetic and evolutionary analyses reveal two whole-genome duplication(WGD)events and two paleo-subgenomes in pecan and walnut.Time estimates suggest that the recent WGD event and considerable genome rearrangements in pecan and walnut account for expansions in genome size and chromosome number after the divergence from bayberry.The two paleo-subgenomes differ in size and protein-coding gene sets.They exhibit uneven ancient gene loss,asymmetrical distribution of transposable elements(especially LTR/Copia and LTR/Gypsy),and expansions in transcription factor families(such as the extreme pecan-specific expansion in the far-red impaired response 1 family),which are likely to reflect the long evolutionary history of species in the Juglandaceae.A whole-genome scan of resequencing data from 86 pecan scab-associated core accessions identified 47 chromosome regions containing 185 putative candidate genes.Significant changes were detected in the expression of candidate genes associated with the chitin response pathway under chitin treatment in the scab-resistant and scabsusceptible cultivars‘Excell’and‘Pawnee’.These findings enable us to identify key genes that may be important susceptibility factors for fungal diseases in pecan.The high-quality sequences are valuable resources for pecan breeders and will provide a foundation for the production and quality improvement of tree nut crops.
