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 Colombia
Pathology. CIAT Cali-Palmira, Colombia.
g.m.mosquera@cgiar.org
INTRODUCTION
Rice panicle blight produced by Burkholderia glumae has been reported in
several rice‐producing 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 of Filled
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 seeds Down seeds
Controls
in which B. glumae was detected on symptomatic and apparently healthy a)empty b)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 natural
B. 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 non‐pigmented 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 also
performed. Likely colonies were purified and used on pathogenicity
test on rice seedlings (Fig 4).
C
Figure 1. A, panicle blight symptoms on infected field and B, typical colonies of its causal agent B.
g p g y p yp g Figure 4 Symptoms produced by B glumae on rice seedlings 7 days after inoculation
4. 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 Cordoba
specific detection of B glumae on rice contaminated seeds.
and Sucre (Colombia).
( )
• L concentrations of b t i l present on symptomless seeds
Low t ti f bacterial t t l d
• Three weeks old Colombia 21 variety seedlings obtained from
were also detected by our diagnostic method.
certified seeds.
• Bacterial strains isolated from positive samples for PCR induced
• B. glumae specific primers for 16‐23S intergenic ribosomal region
symptoms on rice seedlings.
amplification reported by Sayler et al, 2006.
• Strains identified as B glumae by PCR and pathogenicity tests
showed variable morphology on agar plates .
h d i bl h l l t
RESULTS • Sequencing data will allow to determine if pigment production
• PCR‐based 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 603‐610.
assay (Fig 3A). B. glumae was detected on asymptomatic seeds where Zeigler, 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. FTG‐311/2005