Analysis Of Aroma Components, Color And Related CmCCD1Expression In Different Varities Of Melon (Cucumis Melo L.) Fruit

Melon quality is affected by a combination of factors such as amora，maturity andcolour.In the past decade, most researchers has focused on the difference of aromacompositions for several cultivers,However,the relationship among aromacharacteristics,carotenoids and related enzyme gene is not reported.In this study,17parents lines and6hybrids were used as materials,their aromatic compounds detectedby SPME and GC-MS were made a comparsion at harvest and three maturitystages.Besides,the correlation between flesh color and contents of carotenoidsespecially β-carotene which was analyzed by HPLC was explored.Furthermore,theexpression level of Carotenoid Cleavage Dioxygenase in melon（CmCCD1）wereobtained by realtime PCR analysis in different color and developing fruits. All theabove are helpful for regulation of aroma volatiles and fruit colour，which presentsimportant references for melon quality breeding. Results were summarized as follows:(1)258volatiles was identified in all melon accessions，including19non-acetateesters,101acetate esters，54alcohols,20aldehydes,17ketones and47other volatilessuch as acid,phenol and7sulfur-containing compounds. As major aromaticcompounds, content of non-acetate esters was highest in var.cantalupesis.（2）Principal component analysis（PCA）was performed on47major aromacomponents in17parent lines and6hybirds,result showed that different types hadcharacteristic volatiles of their own. Butanoic acid,2-methyl-, ethyl ester，Hexanoicacid, ethyl ester, Benzeneacetic acid, ethyl ester were taken as the typical aroma ofmost muskmelons.While Sulfide, allyl methyl, Hexanoic acid, cyclohexylester,Eugenol were the most abundant volatiles in var.makuwa and their F1.the levelof unsaturated C9aldehydes were the highest in BLC（var.conomon）,such as Nonanaland (E,Z)-2,6-Nonadienal. Besides, dynamic changes of these melons’ volatiles inthree maturity stages are compared, the total content and numbers of aroma inmuskmelon was continuously increasing. However, subtle changes happened on othermelons. Alteration of total volatiles is mainly caused bychanges of aroma varieties,non-acetate esters, alcohols and aldehydes.(3) Result of34charecterestic aroma of4F1after PCA revealed that contents oftheir typic volatiles were between parent lines. Analysis of volatiles for severalsegregations of BLC Cha and Cha Que displayed that aroma amount andnumbers in most meterials were closed to or higher than Cha,their relative content of actate asters,non-actate asters,alcohols and aldehydes were also between parents,butlarge difference was exsited among each other.（4）Carotoids was the predominant pigment in orange-fleshed melons, reachinglevels of5.87~20.64μg/g,which was higher than5~20times compared to pale greenor white ones，in which β-carotene’s proportion ranged from70.6%to91.3%and itscontent changed differently in those accessions. Besides, a*was significantlycorrelated with content of carotenoids and β-carotene.(5) CmCCD1gene expression was upregulated upon fruit development in allmelons by Real-time PCR, despite the pale and green ones lack of dihydroactinolide.The expression levels in mature fruit were2~13times higher than the levels found inunripe stage. The expression levels of CmCCD1in matured orange melon was up to6times higher than the pale and green ones, showed the deeper the orange flesh colorthe higher the level.