Estudo da formação de compostos orgânicos voláteis em frutos de melão climatérico e não-climatérico ao longo da maturação

Abstract

Melon (Cucumis melo L.) is a cultivated species of great importance worldwide. Brazil ranks the sixteenth position in its production, especially with the 'Yellow' melon variety, which is the most important fresh fruit exported by the country. Melon fruits also present a wide diversity in characteristics, having both climatic and non-climatic varieties within the species, what makes it extremely important for studies related to fruit ripening and quality attributes, enabling the comparison of behavior across genotypes with different types of maturation patterns and different quality characteristics. One of the main quality attributes in fruits is the aroma, which combined with the taste composes the flavor, one of the main indicators for consumer appreciation in a vegetable. Some genes related to the biosynthesis of volatile organic compounds (VOC) have already been identified in several varieties of melons, as well as hundreds of volatiles that make up the total aroma formation in these fruits. It is, therefore, the goal in this study to bring forth the expression profile of seven genes that encode enzymes related to the formation of VOCs (CmLOX9, CmLOX18, CmBCAT1, CmArAT1, CmPDC1, CmADH1, and CmAAT1) as well as to analyze the pattern of the VOCs related to them and bring a correlation between the gene expression and the detected amount of these compounds in Eldorado (non-climacteric 'yellow' melon) and Gaucho (climacteric) melons. For the analysis of the genes, it was used RT-qPCRs with the cDNA of three different fruits both at 35 and 45 days after pollination (D.A.P), using specific primers designed for each of the genes. Volatile data were collected by SPME-GC-MS TOF using fruit samples at 15, 25, 35 and 45 D.A.P. a Pearson method was used to base the correlation between the genes and the VOCs. The total VOCs composition in Eldorado melon consisted mostly of aldehydes, alcohols, and hydrocarbons as for Gaúcho of esters, aldehydes, and alcohols. Considering the interaction between the volatiles and the genes, we found a positive correlation between CmLOX9 and the VOC (E, Z) -2,6-nonadienal in Eldorado melons; a negative correlation of CmLOX18 with hexanol in Gaucho. The VOCs 2-methylbutanol, ethyl 2-methylbutanoate, 2-methyl propanol, and ethyl 3-mehtylbutanoate were positively correlated to CmBCAT1 in Gaucho and 2-methylbutyl acetate in Eldorado. CmPDC1 showed a positive correlation with butyl acetate, 2-methylbutyl acetate, 2-methylpropanol e 2-methylpropyl acetate in Gaucho. CmADH1 demonstrated a positive correlation with hexanol in Eldorado and a negative correlation with 2-mehtylbutanol in Gaúcho. This is the first time that these genes and volatiles have been identified in ‘Yellow’ melons, which are the main type of melons grown in Brazil and Gaucho melons, which have high commercial expression in the south of the country. This information allows a panoramic look at how the mechanisms responsible for imparting the aroma of these varieties work and provides valuable information for application in studies to improve quality attributes, making these fruits more attractive and generating great visibility to Brazil on the world stage with their production.