Genetic Diversity of Pseudomonas syringae pv. actinidiae Strains from Different Geographic Regions in China

Pseudomonas syringae pv. actinidiae causes kiwifruit bacterial canker, with severe infection of the kiwifruit plant resulting in heavy economic losses. Little is known regarding the biodiversity and genetic variation of populations of P. syringae pv. actinidiae in China. A collection of 269 strains of P. syringae pv. actinidiae was identified from 300 isolates obtained from eight sampling sites in five provinces in China. The profiles of 50 strains of P. syringae pv. actinidiae and one strain of P. syringae pv. actinidifoliorum were characterized by Rep-, insertion sequences 50, and randomly amplified polymorphic DNA polymerase chain reaction (PCR). Discriminant analysis of principal coordinates, principal component analysis, and hierarchical cluster analysis were used to analyze the combined fingerprints of the different PCR assays. The results revealed that all isolates belonged to the Psa3 group, that strains of P. syringae pv. actinidiae from China have broad genetic variability that was related to source geographic region, and that Chinese strains can be readily differentiated from strains from France but are very similar to those from Italy. Multilocus sequence typing of 24 representative isolates using the concatenated sequences of five housekeeping genes (cts, gapA, gyrB, pfk, and rpoD) demonstrated that strain Jzhy2 from China formed an independent clade compared with the other biovars, which possessed the hopH1 effector gene but lacked the hopA1 effector gene. A constellation analysis based on the presence or absence of the four loci coding for phytotoxins and a cluster analysis based on the 11 effector genes showed that strains from China formed two distinct clades. All of the strains, including K3 isolated in 1997 from Jeju, Korea, lacked the cfl gene coding for coronatine. In contrast, the tox-argK gene cluster coding for phaseolotoxin was detected in K3 and in the biovar 1 strains (K3, Kw30, and Psa92), and produced a false-positive amplicon for the hopAM1-like gene in this study. To date, only one biovar (biovar 3) is represented by the strains of P. syringae pv. actinidiae from China, despite China being the center of origin for kiwifruit

Pseudomonas syringae pv. actinidiae (PSA) Isolates from Recent Bacterial Canker of Kiwifruit Outbreaks Belong to the Same Genetic Lineage

Intercontinental spread of emerging plant diseases is one of the most serious threats to world agriculture. One emerging disease is bacterial canker of kiwi fruit (Actinidia deliciosa and A. chinensis) caused by Pseudomonas syringae pv. actinidiae (PSA). The disease first occurred in China and Japan in the 1980s and in Korea and Italy in the 1990s. A more severe form of the disease broke out in Italy in 2008 and in additional countries in 2010 and 2011 threatening the viability of the global kiwi fruit industry. To start investigating the source and routes of international transmission of PSA, genomes of strains from China (the country of origin of the genus Actinidia), Japan, Korea, Italy and Portugal have been sequenced. Strains from China, Italy, and Portugal have been found to belong to the same clonal lineage with only 6 single nucleotide polymorphisms (SNPs) in 3,453,192 bp and one genomic island distinguishing the Chinese strains from the European strains. Not more than two SNPs distinguish each of the Italian and Portuguese strains from each other. The Japanese and Korean strains belong to a separate genetic lineage as previously reported. Analysis of additional European isolates and of New Zealand isolates exploiting genome-derived markers showed that these strains belong to the same lineage as the Italian and Chinese strains. Interestingly, the analyzed New Zealand strains are identical to European strains at the tested SNP loci but test positive for the genomic island present in the sequenced Chinese strains and negative for the genomic island present in the European strains. Results are interpreted in regard to the possible direction of movement of the pathogen between countries and suggest a possible Chinese origin of the European and New Zealand outbreaks

Biological control of kiwifruit and tomato bacterial pathogens

Biocontrol of bacterial pathogens is effected by using cupric salts associate to appropriate agronomical practices such as seed certification, irrigation and fertilization. In in vitro and in in vivo tests, aqueous extracts from Allium sativum and Ficus carica fruits reduce the survival and the damages (disease incidence and disease severity) caused by bacterial pathogens of kiwifruit (Pseudomonas syringae pv. syringae, Pseudomonas viridiflava) and of tomato (Pseudomonas syringae pv. tomato) plants. In vitro tests, both vegetal extracts show antimicrobial activity against all bacterial strains utilised at different concentrations (106 – 108 cfu ml-1). In vivo tests Allium sativum and Ficus carica extracts confirm their antimicrobial activity on P. s. pv. tomato reducing DI and DS after two weeks until to 60% and 67% and to 32% and 22%, respectively

Increased susceptibility to Pseudomonas syringae pv. syringae and Pseudomonas viridiflava of kiwi plants having transgenic rolABC genes and its inheritance in the T1 offspring

L'articolo è disponibile sul sito del nuovo editore http://onlinelibrary.wiley.comThe staminate kiwi (Actinidia deliciosa A. Chev) cv. GTH (Late Yellow Hayward) showed high resistance to the pathogens Pseudomonas syringae pv. syringae and Pseudomonas viridiflava, contrary to the pistillate cv. Hayward which was highly susceptible to both bacteria. The resistant staminate GTH acquired susceptibility when transformed with rolABC of Agrobacterium rhizogenes. This susceptibility was inherited by the T1 offspring containing rolABC genes, derived by crossing pollen of transgenic rolABC GTH with the pistillate cv. Hayward. The susceptibility was probably correlated to high nitrogen content in the leaves of the rolABC plants. The higher susceptibility to P. s. pv. syringae than to P. viridiflava could be correlated with the high degree of auxin production by first bacterium. The high resistance to both bacteria of the staminate GTH was inherited by all the offspring lacking rolABC genes. The possibility of reducing susceptibility of rolABC plants to the pathogens by applying fewer fertilizers in the orchards, which would reduce both costs and environmental impact, is discussed