[Show abstract][Hide abstract] ABSTRACT: The emergence of a new genotype and pathogenic variant of Ralstonia solanacearum in Martinique is described. Bacterial wilt of solanaceous crops caused by phylotype-I and -II strains ('historical strains'), was reported in Martinique in the 1960s. From 1999, Anthurium and cucurbit production was strongly affected by strains described as a new pathogenic variant genotyped phylotype IIB/sequevar4NPB (phIIB/4NPB). The following questions concerning these strains were investigated: (i) were they introduced or endemic, (ii) was their distribution widespread in Martinique, and (iii) which factors Could explain this emergence? This study examined 221 isolates collected from 1989 to 2003 after several surveys. The main Survey (2002-03) included 115 vegetable and ornamental crop farms. From 1999 to 2001, these phIIB/4NPB strains were initially described as the 'Anthurium-cucurbit' strain. In 2003, they made up one-third of the isolates recovered from solanaceous hosts, particularly tomato. This pathogenic variant of R. solanacearum was consistently recovered from wild species and several weeds throughout Martinique, Suggesting that these strains were well established in Martinique. Data reported are consistent with the emergence of 1 new Population of R. solanacearum in Martinique, which has spread rapidly across the entire island and may overtake the previously established population, particularly on tomatoes. Evidence is presented which suggests that the emergence of these new strains is more frequent on vegetable crops when cucurbitaceous and musaceous plants are grown in succession.
[Show abstract][Hide abstract] ABSTRACT: We investigated a destructive pathogenic variant of the plant pathogen Ralstonia solanacearum that was consistently isolated in Martinique (French West Indies). Since the 1960s, bacterial wilt of solanaceous crops in
Martinique has been caused primarily by strains of R. solanacearum that belong to either phylotype I or phylotype II. Since 1999, anthurium shade houses have been dramatically affected by
uncharacterized phylotype II strains that also affected a wide range of species, such as Heliconia caribea, cucurbitaceous crops, and weeds. From 1989 to 2003, a total of 224 R. solanacearum isolates were collected and compared to 6 strains isolated in Martinique in the 1980s. The genetic diversity and phylogenetic
position of selected strains from Martinique were assessed (multiplex PCRs, mutS and egl DNA sequence analysis) and compared to the genetic diversity and phylogenetic position of 32 reference strains covering the
known diversity within the R. solanacearum species complex. Twenty-four representative isolates were tested for pathogenicity to Musa species (banana) and tomato, eggplant, and sweet pepper. Based upon both PCR and sequence analysis, 119 Martinique isolates
from anthurium, members of the family Cucurbitaceae, Heliconia, and tomato, were determined to belong to a group termed phylotype II/sequevar 4 (II/4). While these strains cluster with
the Moko disease-causing strains, they were not pathogenic to banana (NPB). The strains belonging to phylotype II/4NPB were
highly pathogenic to tomato, eggplant, and pepper, were able to wilt the resistant tomato variety Hawaii7996, and may latently
infect cooking banana. Phylotype II/4NPB constitutes a new pathogenic variant of R. solanacearum that has recently appeared in Martinique and may be latently prevalent throughout Caribbean and Central/South America.
[Show abstract][Hide abstract] ABSTRACT: Bacterial wilt of Solanaceous crops, described in Martinique in the 1960s, was mainly caused by biovar 3 and biovar 1 strains of R. solanacearum. From 1999, anthurium fields were strongly affected by biovar 1 strains, genotypically identical to insect-transmitted "Moko" (bacterial wilt of banana) strains (MLG25, sequevar 4, ecotype SFR/A), but not pathogenic (NP) on Cavendish Banana. The disease has now spread over the island on a widened range of species and crops (Heliconia caribaea, Cucurbitaceous crops, several weeds). Fegan and Prior (2004) revised the intraspecific classification within R. solanacearum and proposed molecular tools to distinguish 4 phylotypes (I to IV, each of which are subdivided in sequevars) and to discriminate between banana-pathogenic strains and NP within the R. solanacearum strains belonging to phylotype II, sequevar 4. A collection of 215 isolates collected from 1989 to 2003 during several surveys were characterized according to this classification. Isolates from Cucurbitaceae, Heliconia, weeds, as well as most of the anthurium isolates, were typed in this group of new strains belonging to phylotype II sequevar 4NP, which appeared in Martinique in 1998. The isolates from Solanaceae were distributed among new (phylotype II sequevar 4NP) and "historical" strains (phylotypes I and II, biovar 3 and 1 respectively), but the ratio of new strains on tomato has increased dramatically since 2002. These results suggest the emergence of a new population of R. solanacearum in Martinique, with a broad host range, which is most probably endemic (since it is well established on weeds), and is spreading rapidly. This new population may overcome the "historical" population, particularly on tomato. The emergence of these new strains on vegetable crops may be induced by rotations with cucurbitaceous and musaceous plants..