Deciphering the drought tolerance mechanisms in citrus rootstocks

An increasing amount of land is becoming unsuitable for citrus cultivation, mainly due to water scarcity. This study evaluated the physiological and biochemical performance of trifoliate orange ( Poncirus trifoliata) and rough lemon ( Citrus jambhiri) seedlings subjected to water deficit for 12 days. Under these conditions, trifoliate orange was more sensitive than rough lemon and exhibited significant changes in LRWC (64.8% vs 36.7%), gas exchange parameters (71.7% vs 54.3% on average), leaf surface area (18.2% vs 4.9%), chlorophyll fluorescence in dark- and light-adapted leaves (44.5% vs 33.3% on average) and non-photochemical quenching (94.3% vs 28.2%). Moreover, oxidative stress indicators, such as malondialdehyde or hydrogen peroxide, indicated significantly higher values in trifoliate orange than in rough lemon seedlings. They also showed lower antioxidant defense activation. Other biochemical parameters, such as proline, glycine betaine, antioxidant capacity, phenolic content, and total soluble proteins, showed higher levels in rough lemon than in trifoliate orange seedlings. Overall, the better performance of rough lemon in arid conditions could be attributed to its improved ability to prevent water loss and maintain tissue water content. In addition, rough lemon has a more robust antioxidant defense to keep production of reactive oxygen species at low levels.