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Advances and innovative concepts to control Xylella fastidiosa colonization in citrus plants

Alessandra de Souza: Centro de Citricultura Sylvio Moreira - Agronomic Institute (IAC)

<div><em>Xylella fastidiosa</em> is responsible for diseases that affect different crops worldwide. One of them is Citrus Variegated Chlorosis (CVC), which results from the xylem vessels occlusion by<em> X. fastidiosa</em> biofilm. We have been working on two different approaches to control <em>X. fastidiosa</em>: i. transgenic plants and ii. N-acetylcysteine (NAC). For transgenic plants we focus in understanding the <em>X. fastidiosa</em> – plant host interaction to find key genes from both sides that could be used to break this interaction. Overall we are using genes from pathogen and from resistant host to transform susceptible varieties. One gene from the pathogen is <em>rpfF</em>, involved with <em>X. fastidiosa</em> <em>quorum sensing</em>. Transgenic plants carrying <em>rpfF</em> showed high level of CVC resistance in Hamlin and Pineapple sweet orange varieties. On the plant side, we have identified genes associated with <em>X. fastidiosa</em> resistance, such as LRR-RK/Pattern Recognition Receptors and a gene involved with methyl salicylate production. We have verified that transgenic lines expressing such genes were able to activate ROS response, increase the expression of defense related-genes and decrease <em>X. fastidiosa</em> colonization. The second approach is the use of NAC. In previous results we have demonstrated that this molecule shows effectiveness as an antimicrobial compound and biofilm disruption in <em>X. fastidiosa</em>. Here, we show advances in the study of the NAC effect in plants. Two years of evaluation in field where NAC was applied in plants showing severe CVC symptoms, revealed that application of NAC was able to improve fruit size in both diseased and healthy plants, and increased fruit production in healthy plants. Overall we will present new insights where the knowledge of plant-pathogen interaction can be used to obtain plant pathogen resistance.</div>