|YU, XIAOYUE - Nanjing Agricultural University|
|ZHOU, MINGGUO - Nanjing Agricultural University|
Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/17/2016
Publication Date: 7/1/2016
Publication URL: http://handle.nal.usda.gov/10113/62862
Citation: Yu, X., Armstrong, C.M., Zhou, M., Duan, Y. 2016. Bismerthiazol inhibits Xanthomonas citri subsp. citri growth and induces differential expression of citrus defense-related genes. Phytopathology. 106(7):693-701. doi: 10.1094/PHYTO-12-15-0328-R.
Interpretive Summary: Xanthomonas citri ssp. citri (Xcc), a bacterium that causes citrus canker, is responsible for extensive economic losses to the commercial citrus industry. Although the use of copper is a common regimen for the treatment of citrus canker, it does not provide complete protection to the crop; thus the need for a more effective intervention exists. The current study demonstrates the effectiveness of bismerthiazol for the control of citrus canker. The control mechanism of bismerthiazol appears to be twofold: 1) it contains antibacterial properties that can inhibit the growth of Xcc and 2) it can elicit inducible resistance mechanisms in plants through the differential expression of several known pathogenesis-related genes (PR1, PR2, CHI and RpRd1), the NPR genes (NPR1, NPR2 and NPR3), and a priming defense associated gene (AZI1) as was shown in ‘Duncan’ grapefruit. Further investigation revealed the possible mechanism behind the inducible resistance may involve the flavonoid pathway and the SA-dependent defense response. Overall, our results indicate that the ability of bismerthiazol to induce the defense response in ‘Duncan’ grapefruit, whose mode of action involves the SA signaling pathway and the priming defense, may provide protection against citrus canker in the field.
Technical Abstract: Citrus canker, caused by Xanthomonas citri ssp. citri (Xcc), is a serious disease and causes substantial economic losses to the citrus industry worldwide. The bactericide, bismerthiazol, has been widely used to control rice bacterial blight (Xanthomonas oryzae pv. oryzae). In this paper, we demonstrated that bismerthiazol was effective for controlling citrus canker in planta by inhibiting the growth of Xcc and triggering host defense responses. In addition to inhibiting the growth of Xcc in vitro, bismerthiazol also induced the expression of several pathogenesis-related genes (PR1, PR2, CHI and RpRd1) and regulated the expression of NPR genes (NPR1, NPR2 and NPR3) in ‘Duncan’ grapefruit plants in the greenhouse, especially at early treatment times. Meanwhile, we found that bismerthiazol induced the expression of the marker genes CitCHS and CitCHI in the flavonoid pathway and the PAL1 (phenylalanine ammonia lyase 1) gene in the SA biosynthesis pathway at different time points. Moreover, bismerthiazol also induced expression of the priming defense-associated gene, AZI1. Taken together, these results indicate that the induction of the defense response in ‘Duncan’ grapefruit by bismerthiazol may involve the SA signaling pathway and the priming defense, and that bismerthiazol may serve as an effective alternative to copper bactericides for the control of citrus canker.