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- 1. Rice Panicle Blight: An emergent disease in Colombia Fory, P., Prado, G., Aricapa, G., Correa, F., and Mosquera, G. Rice Pathology CIAT, Km 17 Recta Cali Palmira ColombiaPathology. CIAT Cali-Palmira, Colombia. [email protected] INTRODUCTION Rice panicle blight produced by Burkholderia glumae has been reported in several riceproducing countries around the world. Since the first report of this bacterium in 1989 (Zeigler and Alvarez), the disease was never reported as an important problem affecting rice production in Latin America. America In 2007 important yield losses due to the disease were reported by rice producers in the Caribbean coast of Colombia. This disease affect Figure 2. Greenhouse activities as part of information diffusion workshop grain yield directly because the bacteria infect panicles in flowering stage interfering with kernels filling (Fig 1A). Symptoms can also appear on Primer specificity was confirmed by sequencing analysis of PCR seedling stage as long brown lesions on sheath and leaves. product (Fig 3B). One hundred percent of homology with B. glumae There was no report of molecular identification of this bacterium in was obtained from blast search against gene bank database. Colombia, previous identification was based on pathogenicity and biochemical tests. For the first time we are reporting the identification ofFilled A panicle blight causal agent, B. glumae, using molecular approaches complementing pathogenicity tests. Here we are reporting a specific B detection method based on PCR reaction confirmed by DNA sequencing reaction, sequencing, Up seedsDown seeds Controls in which B. glumae was detected on symptomatic and apparently healthya)emptyb)filled c)empty c)filled seeds collected on Colombian rice fields . In the same way, yellowish Empty pigment on solid media has been reported as selection criteria for B. glumae (Fig 1B). Preliminary results show that could be some physiological variation among B glumae strains isolated from naturalB. Figure 3. A, rice grains affected by the disease. B, PCR amplification obtained from macerated infected seeds. seeds.A Not all B. glumae colonies were pigment producers (Fig 1B and 1C). A nonpigmented strain that was PCR positive and pathogenic on seedlings was also isolated (Fig 1C)1C). B Parallel to PCR analysis, bacterial isolation on agar plates was alsoperformed. Likely colonies were purified and used on pathogenicitytest on rice seedlings (Fig 4). C Figure 1. A, panicle blight symptoms on infected field and B, typical colonies of its causal agent B. gpgy p yp g Figure 4 Symptoms produced by B glumae on rice seedlings 7 days after inoculation4. B.inoculation.. glumae on King B agar plates. MATERIALS and METHODS CONCLUSIONS Development of a diagnostic method based on PCR allowed the Infected plant material (panicles) collected from fields in Cordobaspecific detection of B glumae on rice contaminated seeds.and Sucre (Colombia). ( ) L concentrations of b t i l present on symptomless seeds Lowt tif bacterial tt ld Three weeks old Colombia 21 variety seedlings obtained fromwere also detected by our diagnostic method.certified seeds. Bacterial strains isolated from positive samples for PCR induced B. glumae specific primers for 1623S intergenic ribosomal regionsymptoms on rice seedlings.amplification reported by Sayler et al, 2006. Strains identified as B glumae by PCR and pathogenicity testsshowed variable morphology on agar plates . h d i bl h ll t RESULTS Sequencing data will allow to determine if pigment production PCRbased detection method allowed specific detection of B. glumae could remain as an indicator in B. glumae identification. on symptomatic rice seeds. Information diffusion was done to Research on last emerging rice panicle blight disease is in progress Universities and local research institutes by mean of workshops (Fig 2). because it can substantially affect rice production. PCR method sensitivity was assessed by serial dilutions of pure culture of B. glumae. The minimal number of bacteria that was detectable by References PCR was 100 bacteria per reaction.Sayler, R.J., Cartwright, R.D., and Yang, Y. 2006. Plant Disease 90: Filled seeds from an infected panicle were also subject of PCR detection 603610. assay (Fig 3A). B. glumae was detected on asymptomatic seeds whereZeigler, R.S., and Alvarez, E. 1989. Plant Disease 73:368 the bacteria concentration was about 1000 bacteria compared with ten bacteria, times more obtained from symptomatic grains.Funding: Fontagro Project No. FTG311/2005
