Detection and characterization of Ralstonia pseudosolanacearum infecting Eucalyptus sp. in Brazil

Abstract

Ralstonia solanacearum sensu lato causes bacterial wilt in many agronomic crops and tree species economically important worldwide. It is a species complex that has been divided into phylotypes and sequevars, commonly related to geographic distribution. Knowledge of the phylotype composition and genetic variability in populations of this phytopathogenic bacterium is useful for implementing effective control measures. In a survey conducted in 2019, six bacterial strains were obtained from wilted Eucalyptus urophylla trees in plantations located in the municipality of Dom Eliseu, Pará state, Brazil. Multiplex PCR based on the internal transcribed spacer (ITS) indicated that the bacterial strains belonged to two different species, namely R. pseudosolanacearum (phylotype I) and R. solanacearum (phylotype II). In a phylogenetic analysis, the nucleotide sequence of the endoglucanase (egl) gene from eucalypt strains of phylotype I clustered together with sequevar 18 sequences from GenBank. Separation of the strains into two different species was confirmed by repetitive element palindromic PCR (rep‐PCR). Pathogenicity tests demonstrated that the R. solanacearum and R. pseudosolanacearum strains recovered from E. urophylla cause disease in both tomato and eucalypt plants. Until now, only R. solanacearum (Phylotype II) has been reported causing wilt symptoms on Eucalyptus spp. in Brazil. Therefore, the presence of R. pseudosolanacearum and a need for better understanding of its genetic and aggressiveness variability as well as possible differences between the two species should be considered in breeding programmes aimed at the deployment of host resistance.

Molecular characterization and aggressiveness of the Ralstonia solanacearum species complex from Eucalyptus spp. in Brazil

“…In Brazil, the first report of sequevar IIB_4NPB was in 1998 in Cucumis sativus (Wicker et al, 2007), but it is currently widespread in Latin America. Santiago et al (2017) Phylotype I, R. pseudosolanacearum, was first reported in eucalypt in Brazil in the state of Pará (Freitas et al, 2020). Although Lopes and Rossato (2018) In their work, the subpopulation of the Northern region could be clearly differentiated from those of all other geographic regions.…”

“…Until 2020, R. solanacearum was the only species reported infecting Eucalyptus in Brazil (Fonseca et al., 2014). However, R. pseudosolanacearum phylotype I was recently reported causing wilt in eucalypt plantations (Freitas et al., 2020).…”

“…In addition, they allow the selection of the most aggressive isolates to be used in inoculations for screening genotypes with effective resistance. Because of the high genetic diversity of R. solanacearum associated with solanaceous plants (Santiago et al, 2020) and the recent detection of R. pseudosolanacearum also causing BW in eucalypt (Freitas et al, 2020), we hypothesized that a study of the genetic variability of the RSSC population associated with eucalypt in Brazil could provide important information to help guide studies aimed at establishing appropriate disease management strategies.…”

Improved evaluation of the genetic variability of Brazilian strains of Erwinia psidii with newly developed microsatellite markers

“…It is also possible that the association of E. psidii with dieback and wilt of eucalypt was not detected earlier due to disease misdiagnosis over the years, probably because symptoms were mistaken for those caused by Ralstonia spp. (Arriel et al, 2014;Freitas et al, 2020). identify sources of inoculum and routes of transmission (Rache et al, 2019).…”

Validation and use of a qPCR protocol to quantify the spread of Ralstonia solanacearum in susceptible and resistant eucalypt plants

“…solanacearum and R . pseudosolanacearum have already been reported causing bacterial wilt in Eucalyptus (Carstensen et al, 2016; Freitas et al, 2020). In this study, we adapted a qPCR protocol for detection of bacteria of the R .…”