A New Bacterial Disease on Mandevilla sanderi, Caused by Pseudomonas savastanoi: Lessons Learned for Bacterial Diversity Studies

Abstract

Leaf lesions of Mandevilla sanderi were shown to be caused by Pseudomonas savastanoi. While BOX fingerprints were similar for P. savastanoi isolates from different host plants, plasmid restriction patterns and sequencing of plasmid-located pathogenicity determinants revealed that Mandevilla isolates contained similar plasmids distinct from those of other isolates. A repA-based detection method was established.T he ornamental plant Mandevilla sanderi (Dipladenia sanderi [family Apocynaceae]) originating from Middle and South America has become increasingly popular over the last decade, mainly because of its copiously formed red flowers. In 2008, breeders of Mandevilla sanderi observed for the first time large necrotic lesions with chlorotic rings on leaves and tumor formation on stems (see Fig. 1). The potential causal agents isolated from the lesions of leaves of diseased plant material were identified initially by metabolic profiling (Biolog) as Pseudomonas savastanoi pv. glycinea or pv. nerii (data not shown), pathogens of soybean (Glycine max) or oleander (Nerium oleander), respectively. Stem and leaf inoculation of healthy Mandevilla plants with these isolates indeed caused identical symptoms ( Fig. 1) fulfilling Koch's postulates.P. savastanoi strains are Gammaproteobacteria which belong to genomospecies 2 of the Pseudomonas syringae complex (6). Although the species P. savastanoi was established only in 1992 (5), sequencing of the genomes and plasmids of several P. syringae and P. savastanoi isolates reinforced the discussion about the taxonomic affiliation of P. savastanoi, as the core genome is clearly shared by P. syringae and P. savastanoi strains. Several pathovars of P. savastanoi infect woody plants, e.g., P. savastanoi pv. savastanoi is known as an important pathogen of olive trees (Olea europaea) in the Mediterranean area (11). The typical symptoms of olive knot disease, the formation of tumors in the stem and branches, were already described by Theobrast Eresos in the year 300 BC. The disease causes massive yield losses, and breeding for tolerant varieties is the main strategy to overcome the commercial losses due to infections with P. savastanoi pv. savastanoi (16).Taking into account that other known hosts of P. savastanoi are oleander (Nerium oleander) and privet (Liguster vulgare), leaf and stem inoculations of Mandevilla isolates were done also on oleander, olive, and privet plants. Nine weeks after inoculation, the response patterns of oleander were similar to those observed on Mandevilla plants; however, while no symptoms were observed for olive plants, privet plants displayed only leaf lesions (unpublished results). Thus, it was hypothesized that the most likely causal agent of the novel bacterial disease of Mandevilla sanderi might have originated from infested oleander plantations in the vicinity of the Mandevilla sanderi-producing companies in the South of France. To shed light on this hypothesis, P. savastanoi isolates from Mandevilla sanderi were characterized and compared to isolate...

Plasmid Detection, Characterization, and Ecology

“…However, the isolates could clearly be distinguished based on their plasmid content. Based on their repA sequence the plasmids were assigned to the pAT family [60]. …”

Genetic and phenotypic diversity of Mediterranean populations of the olive knot pathogen, Pseudomonas savastanoi pv. savastanoi

“…Some strains are able to infect other woody plants besides olive, such as oleander ( Nerium oleander ), ash ( Fraxinus excelsior ), jasmine ( Jasminum officinalis ), privet ( Ligustrum japonicum ), Forsythia spp., Phillyrea spp. (Bradbury, ), Retama sphaerocarpa (Garcia De Los Rios, ), myrtle ( Myrtus communis ), buckthorn ( Rhamnus alaternus ) (Saad & Hanna, ), Mandevilla sanderi (Eltlbany et al ., ) and pomegranate ( Punica granatum ) (Bozkurt et al ., ). Based on differences in host range and other phenotypic and genetic data, the species is divided into the following pathovars: pv.…”

Knots Untie: Molecular Determinants Involved in Knot Formation Induced by Pseudomonas savastanoi in Woody Hosts

“…In contrast, the host range of Psr isolates is restricted to Spanish broom (Janse, 1982; Iacobellis et al, 1998; Ramos et al, 2012). Knot formation by P. savastanoi has also been described in several other hosts, including jasmine (Gardan et al, 1992b), privet (Gardan et al, 1992b), mock privet (Gardan et al, 1992b), forsythia (Bradbury, 1986), buckthorn (Temsah et al, 2007a), fontanesia (Mirik et al, 2011), pomegranate (Bozkurt et al, 2014), myrtle (Goumas et al, 2000; Temsah et al, 2007b; Cinelli et al, 2014) and dipladenia (Putnam et al, 2010; Eltlbany et al, 2012; Pirc et al, 2014; Caballo-Ponce and Ramos, 2016) ( Table 1 ). Although these P. savastanoi hosts are classified in several plant families, over 50% of them belong to the Oleaceae family.…”