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

Integration of chitosan coating and short-term hypobaric treatment extends postharvest life and upregulates defense-related enzymes in apple fruit

The limited postharvest life of fresh horticulture products can be ascribed to various factors among which diseases and disorders play an important role, leading to product and economic losses. Bull’s eye rot caused by Neofabraea perennans is one of the postharvest fungal diseases of apple fruits. We studied the efficacy of combined short-term hypobaric treatment and chitosan coating on fruit quality, disease incidence and consumer acceptability of apple fruits, after artificially inoculating the apples with N. perennans. Fruit were treated with hypobaric pressure (50 kPa for 4 h) and/or coated with 0.5%, 1%, and 2% chitosan, and a combination of both. All fruits were then stored for 120 days at 4 ± 1°C and 85 ± 5% RH followed by sensory evaluation at simulated retail conditions for 15 d at 20 ± 3°C and 65 ± 5% RH. Results showed that hypobaric treatment and chitosan coating, either alone or in combination, significantly affected enzyme activity, development of bull’s eye rot, physicochemical quality, and acceptability of apple fruit during storage. Among all the treatments, the best results were obtained by hypobaric treatment combined with 2% chitosan coating, which significantly maintained firmness (71.01 N), TSS (13.0 obrix), TA (0.34%), ethylene production rate (0.78 μmol kg−1 h−1), and respiration rate (0.40 mmol kg−1 h−1), increased the activity of Chitinase, Glucanase and Phenylalanine ammonia lyase (80, 133.67, and 156.7 U g−1 FW respectively), and prevented rot development (0%) until day 120. Moreover, the combined treatment had comparatively better overall acceptability (8.40) during its shelf life compared with control and individual treatments. However, further investigation is needed to evaluate the commercial feasibility of the study