LAUSR

Background: RGL mandarin is one of the important mandarin citrus varieties in Indonesia. The tolerance of RGL mandarin citrus to water deficit can be induced by the rootstock. This study aimed to characterize the physiological responses and transcriptional gene expression of RGL mandarin citrus grafted onto three rootstock genotypes during the dry and the rainy seasons.Methods: Three-years-old mandarin citrus trees cv. Rimau Gerga Lebong (RGL) grafted onto three citruses (JC, Cit and K) were planted at the experimental field of the ICISFRI. The experiment was conducted with a randomized block design and each scion-rootstock combination contained five replications. All of the physiological and relative gene expression parameters observed were conducted at the last of the dry season (September 2019) and the mid of the rainy season (January 2020). Water deficit was induced by no watering plants during the dry season.Result: The results of physiological responses and relative gene expression analyses showed that RGL-Cit combination had better than RGL-JC combination and RGL-JC combination had better than RGL-K combination. RGL-Cit combination showed less wilt than RGL-JC and RGL-K combinations. The RGL-Cit combination had the highest stomatal density, stomatal aperture, stomatal conductance and photosynthetic rate in the dry season. Different plant combinations showed different gene expressions. RGL-JC and RGL-K combinations were upregulated in almost all the primers related to drought responses tested in the dry season. RGL-Cit combination only upregulated the PIP1, PIP2 and ACS2 and unregulated the others in the dry season. Therefore, citrumelo seems to be a valuable type of rootstock.