Abstract
The present study was undertaken to determine developmental variation in the free amino acid content of leaves and berries of muscadine and Florida bunch grape genotypes. Leaf and berry samples were collected at six developmental stages from fifty-four grape genotypes with varying genetic background, and analyzed for total free amino acid content. Free amino acid content of the leaves varied from 0.7 mg·g[sup-] to 13.7 mg·g[sup-] fresh leaf at pre-flowering stage; 1.5 mg·g[sup-] to 13.2 mg·g[sup-] fresh leaf at flowering stage; 1.4 mg;g[sup-] to 5.8 mg·g[sup-] fresh leaf at young fruit stage; 1.5 mg·g[sup-] to 7.5 mg·g[sup-] fresh leaf at medium fruit stage; 1.5 mg·g[sup-] to 10.4 mg·g[sup-] fresh leaf at mature fruit stage; and 1.4 mg·g[sup-] to 8.5 mg·g[sup-] fresh leaf at ripe fruit stage. Accumulation of amino acids in berries varied from 0.8 mg·g[sup-] to 4.5 mg·g[sup-] fresh tissue at young fruit stage; 0.8 mg·g[sup-] to 4.9 mg·g[sup-] fresh tissue at medium fruit stage; 0.8 mg·g[sup-] to 1.16 mg·g[sup-] fresh tissue at mature fruit stage; and 1.2 mg·g[sup-] to 17.0 mg·g[sup-] fresh tissue at ripe fruit stage. The results showed wide variation in the leaf amino acid content among the genotypes and was highly significant (P 0.05) for different developmental stages and for the grape genotypes. The berry amino acid content was significantly different (P 0.05) between developmental stages but not among the genotypes. Based on the amino acid accumulation pattern in the leaves, the grape genotypes were categorized into six groups. Amino acid accumulation patterns at different developmental stages between these groups have been discussed. Determining the relationship between accumulation patterns of leaf amino acids with that of berry amino acids will help in understanding source and sink relationships, vine health, and juice and wine quality.
