Detection of Xanthomonas oryzae by loop-mediated isothermal amplification
J. M. LANG (1), P. Langlois (1), H. Nguyen (2), C. M. Vera Cruz (3), L. Purdie (4), T. Holton (4), A. Djikeng (4), V. Verdier (5), J. E. Leach (1). (1) Colorado State University, Fort Collins, CO, U.S.A.; (2) International Rice Research Institute, Los Banos, Philippines; (3) International Rice Research Institute, Metro Manila, Philippines; (4) Biosciences Eastern and Central Africa, Nairobi, Kenya; (
Molecular diagnostics of crops and livestock diseases play an important role in enhancing food security. A recent advance in molecular diagnostics is the novel loop-mediated isothermal amplification (LAMP) method. LAMP allows for rapid, highly specific amplification of target DNA sequences at a single temperature, and is ideal for field-level analysis. Rice is a staple crop for much of the world’s population, including that of sub-Saharan Africa. Two important rice diseases are caused by <i>Xanthomonas</i> species. <i>X. oryzae</i> pv. <i>oryzae</i> (Xoo) colonizes xylem vessels and causes bacterial blight (BB), while <i>X. oryzae</i> pv. <i>oryzicola</i> (Xoc) colonizes spaces between leaf parenchyma cells to cause bacterial leaf streak (BLS). Both pathogens represent a significant threat for agriculture and global food security, and are considered quarantine organisms in all rice growing countries. We adapted existing genomics-based molecular diagnostic tools for these pathogens into a reliable, sensitive LAMP assay. The specific presence of each pathogen was detected from DNA, cells, leaf and seed samples. Thresholds of detection were consistently 10<sup>3</sup> CFU/ml of cells and 1 fg of genomic DNA. LAMP for both BB and BLS pathogens will allow surveillance activities in rice fields as well as testing of imported materials by quarantine offices.
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