| Any factors that influence vine growth directly or indirectly impact fruit metabolism and lead to large variation in fruit quality.Grapevine is sensitive to climate changes,such as temperature,sunlight,and water status.The seasonal fluctuations on fruit composition are mainly resulted from climate variability.A double cropping system has been commercially adopted in southern China under subtropical monsoon climate,where there are abundant sunshine and heat resources.Due to climate differences between summer and winter growing seasons,the fruit metabolism varies greatly.In this study,we conducted targeted metabolome and transcriptome analyses on summer and winter grape berries of’Cabernet Sauvignon’(C),’Riesling’(R),’Victoria’(V)and ’Muscat Superior’(Y)at green,pre-veraison,post-veraison and harvest stage in 2014 and in 2015 grown under double cropping system,to analyze the variation on flavonoid and volatile compounds between two crops during fruit development,for the purpose of dissecting the potential regulation of growing season on fruit metabolism,which will provide knowledge to improve fruit quality.The results here showed that:1)the daily temperature showed reverse evolution pattern in two growing seasons from budbreak to harvest.The temperature in summer cropping cycle increased gradually and frequently exceeded 35℃,while the temperature decreased during the winter cropping cycle,with a mean temperature of approximately 20℃,resulting in the difference on duration of phenological phase between two crops.Overall,winter cropping advanced the onset of veraison and accelerated ripening progression.As for physicochemical characteristics at harvest,winter grapes tended to have smaller berries and higher total soluble solids than these in summer grapes.2)targeted metabolome showed some varietal and seasonal specificities.Principal component analysis could distinguish C and R with V and Y,and winter grapes accumulated more abundant of flavonoids and volatile compounds.The metabolic markers of winter grapes were free hexanal,benzeneacetaldehyde and glycosidically bound cis-furan linalool oxide.3)as for transcriptome at harvest,principal component analysis could distinguish wine grapes with table grapes,and summer grapes with winter grapes.Additionally,the common upregulated DEGs were significantly enriched on ’Secondary metabolic process’,while the common downregulated DEGs were enriched on ’Photosynthesis’ and ’Response to stimulus’.4)flavonoid pathways were boosted in winter grapes at metabolite and transcriptional level.Various genes and transcription factors in flavonoid pathway were upregulated in winter grapes,accordingly,the contents of anthocyanins and flavonols were drastically promoted.5)the influence of growing season on volatile compounds was complicated.In most cases,the terpenes were higher in winter grapes than in summer grapes,probably due to the upregulation of VviDXS1,VviDXR,VviHDR and VviTPSs.The content of P-damascenone was higher in winter grapes of R,V and Y,which was in accordance with the upregulation of VviCCD1.The accumulation pattern of C6 aldehyde was correlated with the expression profile of VviLOXA,which might contribute to the variation of C6 aldehyde.6)furthermore,tricarboxylic acid cycle related genes were hastened in winter grapes,whereas genes in other primary metabolism were up and down modulated.Overall,the target metabolome and transcriptome were different between two crops.Flavonoids and volatile compounds were affected by the growing season at both the metabolite and transcription level.Winter grapes were characterized by more abundant of flavonoids and aroma compounds,showing a better fruit quality than summer grapes. |
