Clavibacter michiganensis subsp. michiganensis strains from central Chile exhibit low genetic diversity and sequence types match strains in other parts of the world

Abstract

Bacterial canker caused by Clavibacter michiganensis subsp. michiganensis (Cmm) is one of the most important bacterial diseases of tomato. In order to understand the emergence and dissemination of this pathogen in Chile, Chilean Cmm strains isolated from different sites in central Chile were characterized and compared to a worldwide collection of strains. Multilocus sequence analysis and typing (MLSA‐MLST) based on five housekeeping genes, i.e. atpD, dnaK, gyrB, ppk and recA, and multilocus variable number of tandem repeats (VNTR) analysis (MLVA) based on eight VNTRs were used. Low diversity was found using MLSA‐MLST among the 25 Chilean strains, which clustered into three groups, each corresponding to a single sequence type (ST). Group I contained most strains (21/25), isolated over different years from Valparaíso and O'Higgins regions. Group II contained only one strain from Maule region that was isolated in 2005. These two groups belonged to the same genetic lineage. Group III contained three strains from Valparaíso region isolated in 2004, 2012 and 2013. MLVA also distributed the strains into the same three groups. Group III strains shared the same ST as strains from Algeria, Belgium, France, the Netherlands, Uruguay and the USA. Group II strains shared the same ST as strains from Brazil and Uruguay, while Group I strains shared the same ST as two strains of unknown origin. This study shows that Cmm strains from central Chile tend to be clonal and have similar genetic profiles to strains from other countries.

Streptomycin resistance in Clavibacter michiganensis subsp. michiganensis strains from Chile is related to an rpsL gene mutation

“…According to the present analyses, Chilean Cmm resistant strains are arginine mutants. Valenzuela et al (2018) evaluated the pathogenicity of Chilean Cmm strains. Results of pathogenicity tests showed a diversity in severity of disease symptoms, but this variability could not be associated with streptomycin resistance (data not shown).…”

“…Chilean Cmm strains resistant to streptomycin belong to a major group of strains (sequence type ST32), based on MLSA-MLST analyses described by Valenzuela et al (2018). Chilean strains sensitive to streptomycin belong to sequence types ST36 and ST18.…”

“…Four strains from the Molecular Microbiology and Environmental Biotechnology Laboratory culture collection (Chemistry Department, Universidad Tecnica Federico Santa Maria, Valpara ıso, Chile), were isolated from plants with bacterial canker symptoms from O'Higgins Region in 2015. These Cmm strains have been previously identified and characterized (Valenzuela et al, 2018). Cmm strains were routinely cultured in yeast-peptone-glucose (YPG) agar (YPGA; 5 g L À1 yeast extract, 5 g L À1 Bactopeptone, 10 g L À1 glucose, 15 g L À1 agar) and incubated at 28°C.…”

“…Valenzuela et al . () carried out a study of genetic variation in a collection of Cmm strains isolated from tomato fields in different locations in 1996–2015. They found low diversity, clustering the strains in three groups, with most of the strains clustered in a single group.…”

“…The strA and strB genes are commonly clustered on plasmids, and easily transferred to plant pathogens (Chiou & Jones, 1995;Sundin & Bender, 1995;McManus et al, 2002). Valenzuela et al (2018) carried out a study of genetic variation in a collection of Cmm strains isolated from tomato fields in different locations in 1996-2015. They found low diversity, clustering the strains in three groups, with most of the strains clustered in a single group.…”