Physiological and redox status properties of a new late-ripening triploid hybrid mandarin: a seasonal field evaluation

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Introduction In Corsica, citrus cultivation represents a major economic sector, largely based on high-quality products such as ‘Clementine de Corse’ and ‘Pomelo de Corse’, both of which hold a Protected Geographical Indication (PGI). However, the harvesting periods of these cultivars create a recurrent production gap between winter and spring, during which imported citrus fruits dominate the market, increasing competitive pressure on local producers. The development of late-ripening citrus varieties adapted to Mediterranean pedoclimatic conditions therefore represents a key strategy to strengthen local production and extend market availability. In this context, the present study evaluates the seasonal physiological and antioxidant responses of a novel triploid mandarin hybrid (designated W9) grafted onto C35 citrange, in comparison with two reference diploid cultivars, clementine and pomelo (‘Star Ruby’ grapefruit), grown under open-field conditions Methods Seasonal parameters were monitored across four seasons, including gas exchange ( P net , g s , E, iWUE ), chlorophyll fluorescence ( F v /F m ), oxidative stress markers (H 2 O 2 , MDA, proline), ascorbate redox components (Asa, DHA, Asa/DHA), and major antioxidant enzymes (SOD, CAT, APX, DHAR). Results Principal component analysis revealed a strong seasonal structuring of physiological responses, driven primarily by photosynthetic performance and redox metabolism. All genotypes exhibited reduced photosynthetic activity during the cold season. The triploid W9 consistently maintained lower H 2 O 2 and MDA levels, particularly during spring, its harvest period. This was associated with a higher Asa/DHA ratio and increased activities of antioxidant enzymes, notably CAT, APX, and DHAR. Discussion These results suggest that triploidy at the scion level confers improved redox homeostasis without drastically altering photosynthetic capacity, thereby enhancing tolerance to chilling during the winter-to-spring transition. Overall, triploid W9 emerges as a promising late-ripening citrus genotype for Mediterranean production systems, with potential benefits for fruit quality, harvest stability, and reinforcement of the Corsican citrus value chain.

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