Analysis Of Volatile Components In Fruit Development Of Gannanzao Navel Orange And Effects Of Exogenous Abscisic Acid On Its Fruit Ripening

Gannanzao navel orange(Citrus sinensis L.Osbeck)was a bud variety selected from Newhall navel orange,which has the characteristics of strong adaptability,early high yield and very early maturity.At present,the promotion area of the new variety has exceeded 60,000 mu.The southern region is one of the main cultivated fruit trees for the optimization of cultivar structure.Therefore,it is of great significance to study the regulation mechanism in the maturity process for the selection of navel orange varieties with different maturity.In this study,the Gannanzao navel orange(Mutant type,MT)was used as the test material,and the Newhall navel orange(Wild type,WT)was used as the control to study the composition of the volatile components of the fruit during the ripening process.At the same time,the effects of exogenous abscisic acid(ABA)and ABA biosynthesis inhibitor nordihydroguaiaretic acid(NDGA)on the maturation of MT and WT fruits and their endogenous hormone contents were also studied.1.The volatile components of fruits during the ripening of MT and WT were studied.It can be seen that53 volatile components were separated from the two varieties,mainly hydrocarbons,alcohols,aldehydes and esters;there were 34 common components,mainly limonene,linalool and octanal.There were 38 kinds of ingredients,four of which present in MT and not present in WT,namely n-heptanol,elem alcohol,linalyl acetate and isoamyl isobutyrate.49 kinds of volatile components were separated from WT,15 of which were found in WT but not in MT,including β-cedarene,α-cobene,farnesene,octanol,carvacrol,and 4-nonenol..During the fruit development,the relative contents of hydrocarbons and aldehydes in the volatile components of MT were higher than that in WT,while the alcohols and esters were lower than WT.Principal component analysis showed that the main volatile components of MT and WT were similar in 110DAF(days after flowering,DAF)and 140 DAF,while the composition and content of main volatile components in 170 DAF,200 DAF and 235 DAF were different.There were 10 main components affecting the volatile substances in the fruit development period of two navel orange varieties,including valencia menthol,(E)-3,7-dimethyl-2,6-octadienol 3-methyl Butyrate,octyl ether,nobucol,farnesol,octanal,carvacrol,beta-caryophyllene,oleolin and verbena.2.The effects of fruit ripening after immersion treatment with exogenous ABA and NDGA in MT and WT were studied.The results showed that exogenous ABA treatment had no effect on fruit weight,fruit shape index,peel thickness and vitamin C content in the two navel orange varieties.Exogenous ABA treatment accelerated the growth of soluble solids content in the early stage of fruit ripening,but inhibited it at the later stage.At the same time,exogenous ABA treatment promoted the coloration of navel orange fruit;accelerated the decline of titratable acid content.NDGA treatment inhibited the coloration of fruit in navel orange,and also inhibited the decline of titratable acid content,but the content of soluble solids had noobvious effect.3.The effects of exogenous ABA and NDGA treatment on the contents of endogenous ABA and auxin(IAA)in MT and WT during fruit ripening were analyzed.The results showed that exogenous ABA and NDGA treatment inhibited the increase of endogenous ABA content in MT and WT pericarp,and the inhibition effect under NDGA treatment was greater than that of exogenous ABA treatment.However,exogenous ABA treatment promoted ABA content in MT and WT flesh,while NDGA treatment inhibited the increase of endogenous ABA content.Exogenous ABA and NDGA treatment had no effect on IAA content in fruit ripening.