RNA-seq analysis reveals differential transcript expression in citrus accessions susceptible or tolerant to mal secco disease

Lemon is one of the most important citrus fruits cultivated in the Mediterranean basin. However, an important limitation to its production is the presence of the mal secco disease (MSD). MSD is caused by the fungus Plenodomus tracheiphilus and in some areas, highly affected by the pathogen, it causes significant yield losses and death of entire plants. Since then, various studies have tried to identify some cultivars that combine good fruit quality and resistance to MSD. Different cultivars were identified, and although they did not guarantee both high fruit quality and resistance to MSD, they allowed the Sicilian lemon industry to survive. Recently, new breeding techniques (NBTs) represent a good opportunity to achieve the previously mentioned goals. However, the first step before using these techniques is to identify the genes involved in the resistance/tolerance or sensitivity to MSD. With the main purpose of identifying genes involved in the response to MSD, we performed an RNA-seq experiment on three different accessions 'Femminello Siracusano 2Kr' (Citrus limon (L.) Burm f.) and Rough lemon (Citrus jambhiri Lush.), susceptible to MSD, and Cleopatra mandarin (Citrus reshni Hort. ex Tan.), tolerant to the disease, at two different time points, 7 and 14 days after inoculation (DAI). The comparison of differentially expressed transcripts (DETs) highlighted the different responses of accessions susceptible or tolerant to MSD. In fact, the susceptible types had more DETs than the tolerant one; moreover, an increase in DETs was also detected from 7 days to 14 days after inoculation. Preliminary results regarding this RNA-seq will be discussed.