Analysis of the aromatic compounds of four tetraploid muscat flavor grapes and their diploid parents

Abstract: 【Objective】In recent years, breeders and consumers pay more and more attention to tetraploidgrapes because of their big berry size with less seeds and their high yields. The researchers at the Pomolo⁃gy Institute, Shanxi Academy of Agricultural Science bred three tetraploid grape varieties from colchicinetreated hybrid seeds, including‘Zaoheibao’‘Qiuheibao’and‘Wanheibao’with a rose fragrance. Whilerepresenting one of the inherent properties of grapes, there has been no research on the analysis of the aro⁃ma composition between tetraploid and diploid grapes. In order to provide a theoretical basis for further un⁃derstanding of tetraploid grapes, the aromatic compounds of fruits during their ripening period, we analyzed four tetraploid table grapes with muscat flavor including‘Zaoheibao’‘Qiuheibao’‘Wanheibao’and‘Tetraploid Muscat Hamburg’as well as their diploid parents including‘Guibao’‘Zaomeiguixiang’‘Christmas Rose’and‘Muscat Hamburg’.【Methods】The berries were collected during August-Septem⁃ber 2013 from eight grape vines grown in the breeding vineyards of the Pomology Institute, Shanxi Acade⁃my of Agricultural Science in Taigu, China. The samples were frozen using liquid nitrogen and stored in anultra-low temperature freezer. Then the aromatic compounds of the samples were determined in the Col⁃lege of Horticulture Science and Engineering, Shandong Agricultural University in Taian, China, using asolid phase micro-extraction (SPME) and gas chromatograghy-mass spectrometry (GC/MS). According tothe mass spectrometer ion scanning map, the aromatic compounds were quantitatively analyzed by usingthe area normalization method, taking the average score of 3 repeated tests as the basis for the relative con⁃tent of the aroma component. All collected data were analyzed using SPSS13.0 and Excel software for statis⁃tical analysis.【Results】There were significant differences in types and relative content of the aromaticcomponents among the eight grape varieties. There were primarily seven types of aromatic components ingrapes, including alcohol, aldehyde, ketone, ester, olefins, acid and others. There were one or two types ofacid in‘Zaoheibao’and‘Zaomeiguixiang’, respectively, while there was no acid in the other six grape va⁃rieties; in addition, there was no ester in the‘Zaoheibao’. The same aromatic components among the eightgrapes were identified as twelve different types, including three types of alcohols, five types of aldehydes,two types of ketone and two types of olefin. The major aromatic compounds found in the eight grape variet⁃ies are aldehydes, with a relative content of 56.49%-81.63%, especially 2-hexene aldehyde and hexalde⁃hyde with a green leaf flavor and fruity scent, which were the two richest compounds. The 2-hexene alde⁃hyde was the first rich compound identified, with a relative content of 34.40%-49.81%, which was the rich⁃est in‘Qiuheibao’and‘Qiuhong’as tetraploid and diploid grapes, respectively. There were no significantdifferences in the relative content of 2-hexene aldehyde between‘Tetraploid Muscat Hamburg’and‘Mus⁃cat Hamburg’; but the relative content in‘Zaoheibao’and‘Wanheibao’were lower than that in their dip⁃loid parents, while that in‘Qiuheibao’was between its parents. Aldehyde was the second rich compoundidentified, with a relative content of 16.28%-28.43%, which was richest in‘Wanheibao’and‘Qiuhong’as tetraploid and diploid grapes, respectively.‘Tetraploid Muscat Hamburg’had a significantly higher al⁃dehyde content than‘Muscat Hamburg’and the content in‘Zaoheibao’was lower than that in its father‘Zaomeiguixiang’; the ones in‘Qiuheibao’and‘Wanheibao’were significantly higher than that in itsmother‘Guibao’, yet it was lower in‘Qiuheibao’which was lower than that in its father‘Qiuhong’. Terpe⁃noid compounds and their content are closely related to the unique fragrance of roses in Eurasian grapes,especially in the free form of monoterpene. As shown in the results, except for‘Qiuhong’, the rest of theseven rose-fragrant grapes had a high relative content of terpene alcohols (7.24%-28.60%) and all con⁃tained linalool and nerol, which with an aroma of rose wood, green sweet orange fragrance flowers and ros⁃es, respectively. And except for‘Guibao’among the seven rose fragrance grapes, the rest of the six grapescontained geraniol and citronellol, which has an aroma of light sweet rose, green grass and sweet rose, re⁃spectively. The relative content of linalool and geraniol was 4.14%-25.23% in the seven grapes, of whichthe order from high to low in the four tetraploid grapes was:‘Zaoheibao’‘Tetraploid Muscat Hamburg’‘Wanheibao’, and‘Qiuheibao’, while that in the diploid grapes was‘Guibao’‘Muscat Hamburg’and‘Zaomeiguixiang’. The relative content of terpene alcohol in‘Tetraploid Muscat Hamburg’was only3.94% higher than that in‘Muscat Hamburg’, while that in‘Zaoheibao’was 2.07%, 20.21% higher thanthat in its parents‘Guibao’and‘Zaomeiguixiang’, respectively. And it was 13.21% and 7.87% lower in‘Wanheibao’and‘Qiuheibao’than that in their parents‘Guibao’.【Conclusion】Linalool and geraniolwith the fragrance of the rose wood and light sweet rose fragrance respectively played the most importantrole in fruit aroma of the seven grapes with a muscat flavor. According to the results, the relative content ofthe major fragrant substances was not doubled after doubling the chromosome of the diploid rose-fragrantgrapes. The aroma rich degree of the tetraploid grape was related to the strength of the parental rose fra⁃grance. The main fruit aromatic substance found in the eight grapes was C6 aldehyde.