Biodiversity in a Tomato Germplasm for Free Amino Acid and Pigment Content of Ripening Fruits

Abstract

Free amino acid and pigment composition in fruits at two ripening stages from a selected tomato germplasm was stu-died. The aims were contributing to knowledge on variability of ripening metabolism and identifying more consis-tently the genetic background of the plant material under analysis. Significant differences (p < 0.05) were found among ripening stages and among genotypes within ripening stage for all amino acids and pigments except by asparagine, alanine and chlorophyll b contents. The highest relative amino acid content corresponded to glutamate, glutamine, and GABA though some genotypes had relatively high asparagine content. Glutamate, glutamine and GABA performed oppositely: the former increased along ripening while the latter two decreased in their relative content. A Principal Components (PC) analysis was applied, determining that metabolites having the greatest contribution to general variability were threonine, serine, glutamate, glutamine, glycine, isoleucine, leucine, tyrosine, phenylalanine, lycopene and beta- carotene, which showed the highest association with PC1. Alanine and chlorophylls a and b were highly associated to PC2. These two first PC explained the 62% of the total variation, and genotypes were distributed according to the ripening stage in their coordinates. Accordingly, a Hierarchical Clustering resulted in a dendrogram having a relatively high cophenetic correlation (0.70), in which two well defined groups were obtained according to ripening stage. These results verified the existence of variability in the metabolism of ripening fruit for amino acids and pigments, and allowed to identify unequivocally a set of selected tomato germplasm according to the fruit metabolic profiles in these two ripening stages.