Phylogenetic diversity of Clavibacter michiganensis subsp. michiganensis isolates causing bacterial canker of tomato in Greece

Abstract

Tomato bacterial canker, caused by Clavibacter michiganensis subsp. michiganensis (Cmm) (Li et al. 2018), is a common destructive disease worldwide. The bacterium colonizes plant’s vascular system causing characteristic symptoms such as wilting, cankers, brown and black discoloration of vessels, white spots on the fruit and leaves. In the present work, isolates were collected from infected tomato plants of 11 Greek Prefectures during the years 2003-2018, and the genetic variability was investigated. After initial identification, 93 selected Cmm strains were subjected to phylogenetic analyses based on the sequencing of multiple loci (Multi-Locus Sequencing Analysis, MLSA) utilizing four housekeeping genes (atpD, ppk, kdpA and sdhA). MLSA highlighted 4.1% variability in nucleotide sequences and classified the 93 Cmm strains into 38 haplotypes. Nevertheless, the phylogenetic grouping of the strains was not in accordance with the geographical distribution, a fact that probably advocates the introduction of the disease from infected propagating material. However, strains isolated from the same area in a different year were placed in the same group which means that the pathogen can remain active between growing seasons. The study provides important epidemiological information on the disease outbreaks and the spread of Cmm in Greece.

Bacillus Species: Excellent Biocontrol Agents against Tomato Diseases

“…This bacterium colonises plants and reaches the vascular system. The symptoms it causes on the plants depend on the age of the tomatoes and the environmental conditions, but mainly involve mealy spots on the stems, yellowing or wilting of the leaves, and characteristic spots on the fruits known as "bird's eye" (Figure 5) [49]. Bacterial spot of tomato is caused by bacteria from the Xanthomonas group.…”

Allelic variations in a serine protease effector withinClavibacter michiganensispopulations determine pathogen host range

“…Cm populations in Turkey, Italy, and central Chile demonstrated low diversity, suggesting they mainly originated from founder populations that were established endemically in these countries (18) (19) (20). On the other hand, high diversity was observed in Cm populations in Israel, New York State, Argentina, Iran, and Greece (21) (22) (23) (24) (25) suggesting multiple introductions of Cm, presumably through contaminated seeds.…”