Changes in processing tomato fruit quality in heirloom and modern varieties developed over the past decades

Over the past century, the breeding programs for processing tomato (Solanum lycopersicum L.) have focused predominantly on yield optimization and mechanization compatibility, often overlooking critical aspects of fruit quality and flavor that are increasingly valued by consumers. This study investigated the temporal changes in key technological and nutritional traits – sugars, acids, amino acids, ascorbic acid, thiols, carotenoids, volatile fraction (VOCs) and phenolics – and phylogenetic relationships across ten widely cultivated processing tomato varieties released between the early 1900s and 2014. Field trials were carried out in northern Italy under uniform open-field conditions using a completely randomized design. Our analyses revealed significant genetic gains in marketable yield (+0.47 %/year) and in the concentration of guaiacol (+1.66 %/year), a key VOC. Conversely, we observed declines in ascorbic acid (−0.47 %/year), cysteine (−0.87 %/year), glutathione (−1.06 %/year), and seven VOCs (benzaldehyde, heptanal, hexanal, nonanal, 1-octen-3-one, octanal, and 2-pentyl-furan). Correlation analysis indicated inverse relationships between yield and both VOCs and cysteine content. Phylogenetic analysis further suggested that certain quality traits persist within specific genetic sequences of modern varieties. This comprehensive assessment highlights the trade-offs between yield and fruit quality in processing tomato breeding over the past century, providing strategic insights for developing future varieties.