S11 - Session P5 - Physiological and transcriptomic response of different Citrus rootstocks to salt stress

Authors: Mario Di Guardo *, Giulia Modica, Fabrio Arcidiacono, Daria Costantino, Andrea Baglieri, Ivana Puglisi, Stefano La Malfa, Alberto Continella, Alessandra Gentile

Sweet orange ( Citrus sinensis (L.) Osbeck) is the most widely cultivated Citrus species worldwide. For decades, orange cultivation in the Medterranean countries relied on the use of sour orange as rootstock thanks to its adaptability to a wide range of environmental conditions. The rapid spread of tristeza (CTV), a disease affecting the combination with sour orange, has made the selection of novel resistant rootstocks a fundamental goal. Citrus cultivation often relies on the use of non-conventional water resources characterized by high salinity; the present work is aimed at investigating the response of eight CTV-tolerant rootstocks to two degrees of salt stress (30 and 50 mM NaCl). Five of them were selected for their wide use in citriculture: Carrizo and C35 citrange, Citrus macrophylla , Swingle Citrumelo, Citrus volkameriana, whileFurr, Bitters and Carpenter represent new promising rootstocks. The response of one-year-old seedlings of the eight rootstocks was monitored fortnightly through physiological assessments (e.g: xylem water potential, net photosynthesis) for 3 months. At the end of the experiment, morphological measurements (e.g. roots length and leaf area) and the antioxidant enzymes activities (APX, CAT and SOD), involved in response to stress were analysed. Results showed a wide difference in the response to the salt stress with C. volkameriana and Furr characterized by high tolerance to salt stress, while Carrizo and C35 showed a high susceptibility. To further investigate the genetic regulation of the response to salt stress, an RNAseq was carried out on Furr and Carrizo, and the candidate genes detected validated on the remaining samples through a real-time PCR analysis. The combination of morphological, physiological and transcriptomic analysis will provide useful insights for researchers and breeders to decipher the genetic basis behind the different phenotypic response detected.