Effect of fruit load on maturity and carotenoid content of clementine (Citrus clementina Hort. ex Tan.) fruits.
BACKGROUND
Citrus fruits contain many secondary metabolites displaying valuable health properties. There is a lot of interest in enhancing citrus quality traits, especially carotenoid contents, by agronomic approaches. In this study the influence of carbohydrate availability on maturity and quality criteria was investigated in clementine fruits during ripening. Fruiting branches were girdled and defoliated after fruit set to obtain three levels of fruit load: high (five leaves per fruit), medium (15) and low (30).


RESULTS
Considering the soluble solid content/titratable acidity (SSC/TA) ratio, it was found that fruits of the high and medium fruit load treatments reached maturity 1.5 months later than fruits of the control. At the time of maturity the SSC/TA ratio of fruits of all treatments was about 13.6. At harvest, fruits were 23% smaller and total sugar concentration of the endocarp was 12.6% lower in the high fruit load treatment than in the control. In contrast, the concentrations of organic acids and total carotenoids were 55.4 and 93.0% higher respectively. Total carotenoids were not positively correlated with either soluble sugars or total carbohydrates.


CONCLUSIONS
Taken together, the results do not support the common view that carbohydrate availability directly determines carotenoid synthesis by influencing precursor availability.
INRA-UR 1103, Génétique et Ecophysiologie de la Qualité des Agrumes, F-20230 San Giuliano, Corsica, France.
Florine
F
Poiroux-Gonord
Anne-Laure
AL
Fanciullino
Liliane
L
Bert
Laurent
L
Urban
D000143:Acids / Q000378:metabolism*; D000383:Agriculture / Q000379:methods*; D002338:Carotenoids / Q000378:metabolism*; D002957:Citrus / Q000254:growth & development / Q000378:metabolism; D019422:Dietary Sucrose / Q000378:metabolism*; D005638:Fruit / Q000254:growth & development / Q000378:metabolism; D006801:Humans; D018515:Plant Leaves; D012995:Solubility
D000143:Acids; D019422:Dietary Sucrose; D002338:Carotenoids