New Disease Reports
New Disease Reports (2010) 22, 6.
Next > < Prev

New host plants for Ralstonia solanacearum from India

K.N. Chandrashekara 1* and M.K. Prasannakumar 2

*knchandu1@gmail.com

Show affiliations

Accepted: 26 Jul 2010

Ralstonia solanacearum can cause serious losses on many economically important crops. Here, we report two new hosts for Ralstonia solanacearum: davana (Artemisia pallens) and coleus (Coleus forskohlii). Both are important crops in medicinal and aromatic industries in India. Coleus and davana plants showing typical wilt symptoms were found.From these a tentative diagnosis of R. solanacearum was made as a result of oozing from cut stems placed in water.

After isolation from both hosts, morphological studies revealed that bacterial isolates were Gram-negative rod-shaped, non-capsulated and non-spore forming. Isolates grown on SMSA medium (Engelbrecht, 1994) were highly fluidal, white-coloured with a light pink centre and bluish margin and round to irregular shape, typical of R. solanacearum. Electron microscopic studies revealed that bacterium was rod-shaped with one to four polar flagella (Hayward, 1964). Isolates were identified as biovar-III by morphological, physiological, biochemical and pathogenicity studies (Hayward, 1964).

PCR amplification using the OLI 1 and Y2 primers (Seal et al., 1993) gave a 292 bp product with strains from both hosts. A positive result was also obtained using a serological diagnostic kit obtained from the International Potato Research Center, Lima, Peru (Priou et al., 1999). A positive reaction with single chain variable fragment (SCFV) antibody specific to Ralstonia solanacearum further supported the identification.The isolates produced typical wilt symptoms on their respective hosts within five to six weeks after inoculation using root injury (Figs. 1 and 2). Thus, based on morphology, biochemical and nutritional tests and pathogenicity, including ability to cause wilt on solanaceous and non-solanaceous crops, the two isolates were identified as Ralstonia solanacearum biovar-III (Hayward, 1964). Identification of R.solanacearum is further supported by PCR and serological identification. This is the first record of Ralstonia solanacearum causing bacterial wilt of davana and coleus in India.

Figure1+
Figure 1: Bioassay of davana isolates of Ralstonia solanacearum: infected (left), control (right)
Figure 1: Bioassay of davana isolates of Ralstonia solanacearum: infected (left), control (right)
Figure2+
Figure 2: Bioassay of coleus isolates of Ralstonia solanacearum: infected (left), control (right)
Figure 2: Bioassay of coleus isolates of Ralstonia solanacearum: infected (left), control (right)

Acknowledgements

This study was supported by a grant from the NATP-CGP under the project "Molecular approaches for detection of Ralstonia solanacearum". The authors would like to thank Dr. R. D. Rawal and Dr. M. Krishna Reddy for electron microscope studies and suggestions.

References

  1. Engelbrecht, M, 1994. Modification of a semi-selective medium for the isolation and quantification of Pseudomonas solanacearum. ACIAR Bacterial Wilt Newsletter , 3-5.
  2. Hayward AC, 1964. Characteristics of Pseudomonas solanacearum. Journal of Applied Bacteriology 27, 265-271.
  3. Priou S, Gutarra L, Aley P, 1999. Highly sensitive detection of Ralstonia solanacearum in latently infected potato tubers by post-enrichment enzyme-linked immunosorbent assay on nitrocellulose membrane. EPPO-OEPP Bulletin 29, 117-125.
  4. Seal SE, Jackson LA, Young JPW, Daniels MJ. 1993.Differentiation of P. solanacearum, P. syzygii, P. pickettii and the blood disease bacterium by partial 16S RNA sequencing: construction of oligonucleotide primers for sensitive detection by polymerase chain reaction.Journal of General Microbiology 139, 1587-1594.
This report was formally published in Plant Pathology

©2010 The Authors