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Article|09 Sep 2015|OPEN
Rapid screening for citrus canker resistance employing pathogen-associated molecular pattern-triggered immunity responses
Marco Pitino1 , Cheryl M Armstrong1 and Yongping Duan,1 ,
1USDA-ARS, 2001 S. Rock Rd., Fort Pierce, FL 34945, USA
*Corresponding author. E-mail:

Horticulture Research 2,
Article number: 42 (2015)
Views: 657

Received: 12 Jun 2015
Revised: 06 Aug 2015
Accepted: 07 Aug 2015
Published online: 09 Sep 2015


Citrus canker, caused by the bacterial pathogen Xanthomonas citri ssp. citri (Xcc), has been attributed to millions of dollars in loss or damage to commercial citrus crops in subtropical production areas of the world. Since identification of resistant plants is one of the most effective methods of disease management, the ability to screen for resistant seedlings plays a key role in the production of a long-term solution to canker. Here, an inverse correlation between reactive oxygen species (ROS) production by the plant and the ability of Xcc to grow and form lesions on infected plants is reported. Based on this information, a novel screening method that can rapidly identify citrus seedlings that are less susceptible to early infection by Xcc was devised by measuring ROS accumulation triggered by a 22-amino acid sequence of the conserved N-terminal part of flagellin (flg22) from X. citri ssp. citri (Xcc-flg22). In addition to limiting disease symptoms, ROS production was also correlated with the expression of basal defense-related genes such as the pattern recognition receptors LRR8 and FLS2, the leucine-rich repeat receptor-like protein RLP12, and the defense-related gene PR1, indicating an important role for pathogen-associated molecular pattern-triggered immunity (PTI) in determining resistance to citrus canker. Moreover, the differential expression patterns observed amongst the citrus seedlings demonstrated the existence of genetic variations in the PTI response among citrus species/varieties.