| Chinese cherry [Cerasus pseudocerasus(Lindl.)G.Don] belonging to Rosaceae Prunoideae Cerasus Mill.,is a characteristic drupe fruit tree that originated in my country.The fruit of Chinese cherry is bright in color and rich in flavor.It is an ideal fruit tree species for the integrated development of urban agriculture and agricultural tourism.However,in the production of Chinese cherries,there are generally problems of thin peel,soft texture,and intolerance to storage and transportation,which has become one of the bottlenecks restricting the development of Chinese cherry fruit industry.Cultivating excellent varieties of Chinese cherry with high hardness and suitable taste is an important goal to expand the scope of cold chain transportation of Chinese cherries and extend the shelf life of Chinese cherry.The internal structure of the fruit and the physiological components of the cell wall are modified by the cell wall metabolic enzymes,and the cell wall modification enzymes are regulated by a variety of genes and transcription factors.In this study,50 Chinese cherry variety resources(33 local germplasms,17 hybrid germplasms: Hongfei×Pujianghonghua-HP,Hongfei×Nanzaohong-HN,Nanzaohong×Hongfei-NH).The fruit in the mature period was used as material,and the fruit texture parameters were measured by Texture profile analysis(TPA).Through correlation analysis,principal component analysis,and systematic cluster analysis,an evaluation system for Chinese cherry fruit texture quality was preliminarily established.Two Chinese cherries,Hongfei(‘HF’)and Pengzhoubai(“PZB”),from S1 to S8 were used as materials to measure the changes in physiological characteristics such as fruit firmness,anatomical structure.Three stages(S3,S5,and S7)with obvious fruit texture changes were selected for mensuration about cell wall components,related enzyme activities and transcriptome sequencing analysis.The research results are aimed at setting the foundation for analyzing the law of texture change of Chinese cherry fruit,and providing a theoretical basis and genetic resources for the cultivation of new varieties that are resistant to storage and transport.Below are key research findings:1.Evaluation of fruit texture of Chinese cherry germplasms(1)The fruit firmness of 50 Chinese cherry variety resources is 1.41～9.80 N(average:3.80 N),adhesiveness is 0.0829～0.2021 mj(average: 0.13 mj),cohesiveness is 0.18～0.40Ratio(average: 0.3 Ratio),springiness 0.60～2.43 mm(average 1.73 mm),chewiness0.29～4.49 mj(average: 1.97 mj),gumminess 0.29～2.36 N(average: 1.12 N).The coefficients of variation of chewiness(70.61%),gumminess(46.47%)and firmness(43.91%)are relatively large.large(> 5.50 N)and smaller(< 2.00 N)varieties accounted for a smaller proportion,14% and 12%,respectively.(2)The results of correlation analysis of fruit texture parameters showed that there were extremely significant positive correlations between gumminess and chewiness(0.920),firmness(0.901)and springiness(0.802).(3)Principal component analysis was carried out on the fruit texture parameters,and two main factors were extracted based on the eigenvalue greater than 1,and the cumulative variance contribution rate was 89.02%.The comprehensive score model of factor analysis(S=0.707Z1 + 0.2929Z2)shows that the top 10 Chinese cherry germplasm rankings are HYHZZ(Hanyuan black pearl),HN917,NH567,HN968,HF,BJ4(Bijie 4),NH554,HP155,NH702,HP445.(4)The 50 Chinese cherry variety resources were divided into 3 categories by systematic cluster analysis.The comprehensive evaluation index of varieties in category I is higher,and the fruit firmness is also higher;the comprehensive evaluation index of varieties in category II is second,and the adhesiveness is higher;the comprehensive evaluation index of varieties in category III is the lowest,and the texture parameter index are also lower.2.The changes in fruit texture characteristics in Chinese cherry during fruit development(1)During the fruit development process of Chinese cherry,the fruit firmness showed a trend of increasing first and then decreasing.The fruit firmness of HF(5.38 N)was higher than that of PZB(3.57 N)at the mature stage,and the fruit firmness decrease rate of PZB(9.15 N/d)was significantly higher than that of HF(6.78 N/d).(2)Analysis of fruit anatomical structure and morphological parameters showed that during fruit development,the thickness of epidermal cells first increased and then decreased,and the area of parenchyma cells and cells around vascular bundles gradually expanded.The epidermal cells of HF fruit are thicker,the area of parenchyma cells is smaller,and the area of intercellular space is smaller.(3)As the fruits of Chinese cherry mature,the enzyme activities of Cx(Cellulase),β-Gc(β-glucosidase),β-Gal(β-Galactosidase),and PG(Polygalaccuronidase)increase.Under the action of cell wall enzymes,the contents of water-soluble pectin(WSP)and ionic-soluble pectin(ISP)in fruits increased,while the contents of cellulose(CEL),hemicellulose(HC)and covalent soluble pectin(CSP)decreased.The cellulose content of HF was higher than that of PZB,while the overall content of water-soluble pectin was lower than that of PZB overall.(4)Abscisic acid and auxin played a major role in the fruit development of Chinese cherry.(5)Correlation analysis showed that the firmness of Chinese cherry fruit was significantly positively correlated with epidermal thickness and hemicellulose(0.95,0.91).Epidermal thickness was significantly positively correlated with hemicellulose(0.96).The area of parenchyma cells was significantly positively correlated with water-soluble pectin(0.99).The cell area around the vascular was significantly positively correlated with ionic soluble pectin,β-Gal and abscisic acid(0.99,0.97,0.95).Ionic solube pectin was significantly positively correlated with abscisic acid and β-Gal(0.95,0.93).Lignin was significantly positively correlated with auxin and ethylene(0.92,0.92).Cx is highly significantly positively correlated with ethylene(0.92).β-Gc was highly significantly positively correlated with auxin(0.92).β-Gal was significantly positively correlated with abscisic acid(0.94).3.Transcriptome analysis of Chinese cherry during fruit development(1)Based on transcriptome data,7776 differential genes were identified from 18 samples in three stages of HF and PZB.The results of differential gene analysis showed that there were more down-regulated differential genes than up-regulated ones,especially in HFS3 vs HFS7,PZBS3 vs PZBS7,and PZBS7 vs HFS7.The results of GO and KEGG analysis showed that differential genes were significantly enriched in "cell wall metabolism","lignin metabolism and synthesis pathway","hemicellulose metabolism pathway" and "abscisic acid response pathway" during fruit development.Fuzzy c Means clustering results showed that the expression levels of differential genes in clusters 2,3,4,6,8,9,11 and 12 were significantly different in Hongfei and Pengzhoubai.In particular,there are significant differences in the expression levels of differential genes in cluster 9and 11 in Hongfei and Pengzhoubai at different stages.(2)Screen out differential genes related to cell wall metabolism(205),lignin synthesis(64),and plant hormone signal transduction(80).Eight genes in the cell wall metabolism pathway(Cp CSLH1,Cp CSLG2,Cpβ-Glu12,Cp XTH31,Cp XTH22,Cp PG,Cp PME20,Cp PMEI4),two genes in the lignin synthesis pathway(Cp POD21,Cp CCo AOMT),and nine plant hormone signals were identified Genes in the transduction pathway(Cp ASR2,Cp IAA8/17,Cp AUX22/28,Cp AX22 D,Cp GH3.1,Cp AOG,Cp TIFY10A),and five key transcription factors(Cp NAC56,Cp MYB20/44,Cp MADS2,Cp PRE6)were involved in the Chinese cherry.softening process.(3)WGCNA analysis results showed that Y5720,xylan synthesis key enzyme gene F8 H,MCAC1,GLNA in the L-proline synthesis pathway of Bacillus subtilis,microtubule-binding protein TPX2,floral aroma regulation transcription factor ODO1,CSLA2,reading protein ECT2,subtilisin gene SBT16,WAG1,similar to methyltransferase PMT9,and MSTRG.20176 genes may be involved in Chinese cherry fruit softening. |
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