Similarity of amino acid composition of grape berries produced in different years and locations

Abstract

Free amino acids in the juice of four table grope cultivars ('Campbell Early', 'Kyoho', 'Muscat Bailey A', and 'Neo Muscat') grown in eight locations, primarily in the southwest part of Japan, were analyzed in 1992 and 1993. In each cultivar, total amino acids content ranged between 1.0 to 1.8 mM. To compare the similarity in the amino acid composition of berries produced in different years and locations, the pattern similarity index (PSI) was calculated. The PSI is defined as a cosine of the angle (θ) between the amino acid composition of environment A for vector OA (aAsp, aThr,⋯,aArg = a1, a2,⋯,an) and that of environment B for vector OB (bAsp,bThr,⋯,bArg = b1,b2,⋯,bn) in n dimensional space: PSI (OA,OB)=∑i=1naibi/ (∑i=1nai2 ∑i=1nbi2) With regard to the amino acid composition (pattern), the PSI value consisted of the intuitive judgment of similarity on the pattern. As the number of significantly differentiated amino acids increased, the PSI correspondingly tended to be lower. Based on the PSI value, the criterion of classification for pattern similarity of amino acid composition was proposed as follows: over 0.980 as "more similar"; below 0.979 as "less similar". The percentage frequencies of "more similar" patterns, with respect to PSI values, 'Campbell Early', 'Muscat Bailey A', 'Neo Muscat', and 'Kyoho' were 75, 73, 72, and 69%, accounting for about 70% of all pairwise comparisons (nC2). They suggest that the amino acid composition in grape berries is highly similar even if the years and/or locations are different. Each pattern of amino acid composition in the cultivars examined are visually different from each other. When mean concentrations of the individual amino acid were calculated by averaging two years in Fukuoka, the PSI values were 0.959 in 'Kyoho', 0.899 in 'Muscat Bailey A', and 0.753 in 'Neo Muscat' in contrast with 'Campbell Early'. 'Kyoho' vs. 'Muscat Bailey A', 'Kyoho' vs. 'Neo Muscat' and 'Muscat Bailey A' vs. 'Neo Muscat' gave "less similar" patterns with the PSI vaules of 0.979, 0.882, and 0.933, respectively. These results indicate that the amino acid composition in grape berries is a useful marker for ampelographic work.