Genetic Diversity of Zingiberaceae Plant Isolates of Ralstonia solanacearum in the Asia-Pacific Region

Abstract

The genetic diversity of Ralstonia solanacearum strains isolated from Zingiberaceae plants in the Asia-Pacific region was assessed by examining their biochemical properties, discriminating the phylogeny by polymerase chain reaction (PCR), and analyzing the egl and mutS gene sequences. These data were compared with those of reference strains covering the known diversity within the R. solanacearum species complex. Fifty-two of the Zingiberaceae plant isolates belong to either biovar 3 or biovar 4. Multiplex PCR analyses indicated that these strains belong to phylotype I. Phylogenetic analyses revealed that the investigated strains could be further divided into five or more groups and three major groups, based on the egl and mutS gene sequences, respectively. These groups were closely correlated with the host species and/or geographical origin. Our findings suggest that R. solanacearum strains affecting Zingiberaceae plants have multiple origins from within the Asia-Pacific region, and may have been disseminated with seed rhizomes.

Genetic diversity of Ralstonia solanacearum and disease management strategy

“…Since 2005, the pathogen has been spreading to ginger fields in prefectures outside Kochi such as Tochigi (Waki et al 2013). Biovar classification of the isolates from Kochi Prefecture revealed that all of the strains were identical to biovar 4; however, the ginger strains from Tochigi Prefecture belonged to biovars 3 and 4 (Waki et al 2013). …”

“…On the other hand, Japanese strains can be divided into 2 phylotypes (I and IV) and 11 sequevars, and phylotypes I and IV consist of 9 and 2 sequevars, respectively Waki et al 2013). Strains in phylotype II or III have not been isolated so far in the country.…”

“…Phylogenetic analysis based on the egl sequences, Zingiberaceae plant strains in phylotype I derived from Japan and foreign countries were further divided into several major groups, each corresponding closely to six sequevars (Waki et al 2013). These groups were closely correlated with the host species and/or geographic origin.…”

“…Phylotype I strains have been isolated from a wide range of crops and areas, whereas phylotype IV strains have been isolated only from potato cultivation areas. Similarly, some of the sequevars are correlated with specific race, original host and/or geographic origin Waki et al 2013). …”

Bacterial wilt of three Curcuma species, C. longa (turmeric), C. aromatica (wild turmeric) and C. zedoaria (zedoary) caused by Ralstonia solanacearum in Japan

“…In Japan, bacterial wilt of ginger family plants caused by R. solanacearum has been reported on ginger, mioga and siam tulip (curcuma) (Morita et al 1996;Tsuchiya et al 1999;Yano et al 2005), and all strains belonged to race 4, biovar 4 and phylotype I (Waki et al 2013). Japanese race 4 strains also have been subclassified into two DNA types (type I and II) based on repetitive sequence-based PCR (rep-PCR) DNA fingerprint analysis, and PCR primer sets for specific detection, and discrimination of each DNA type within race 4 strains has been reported (Horita et al 2004;Horita and Tsuchiya 2012).…”