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The overall disease incidence of postharvest fruit rots of kiwifruit (Actinidia deliciosa) in Korea averaged 32%, but the incidence ranged from 5% to 68% in the orchards surveyed. The percentage of kiwifruit showing internal and external symptoms were 21.9% and 4.9%, respectively, and an additional 5.2% of the kiwifruit showed both internal and external symptoms. Botryosphaeria dothidea and Diaporthe actinidiae cause ripe rot and stem-end rot, respectively, and were identified as the major postharvest pathogens with average isolation rates of 83.3% and 11.9%. Incidence of the postharvest fruit rots was closely correlated with ripening temperatures favourable to the mycelial growth of the major pathogens. Postharvest fruit rots occurred at all ripening temperatures 11°C and maximum disease incidence was observed at 29°C. No mycelial growth of B. dothidea and D. actinidiae occurred on potato dextrose agar plates under 11°C and the optimum temperature ranges for mycelial growth of the pathogens were 26-35°C and 26-29°C, respectively. The optimum kiwifruit ripening conditions for minimising damage from the postharvest fruit rots were a 20-day ripening at 17°C. Intensive application of fungicides just before or after the rainy season is conducted to control postharvest fruit rots in kiwifruit orchards of Korea. Benomyl WP and thiophanate-methyl WP, registered as preventive fungicides against postharvest fruit rots, are usually applied 5-6 times at 10-day intervals beginning in early June in the kiwifruit orchards. Tebuconazole WP, iprodione WP, and flusilazole WP were selected as alternative fungicides to prevent emergence of fungicide-resistant strains and reduce the number of fungicide applications. The optimum spray programme for controlling postharvest fruit rots was four applications at 10-day intervals from mid June for tebuconazole WP, iprodione WP, and flusilazole WP, compared with five applications for benomyl WP and thiophanate-methyl WP.

Pseudomonas syringae pv. actinidiae causes bacterial canker disease in kiwifruit. Owing to the prohibition of agricultural antibiotic use in major kiwifruit-cultivating countries, alternative methods need to be developed to manage this disease. Bacteriophages are viruses that specifically infect target bacteria and have recently been reconsidered as potential biological control agents for bacterial pathogens owing to their specificity in terms of host range. In this study, we isolated bacteriophages against P. syringae pv. actinidiae from soils collected from kiwifruit orchards in Korea and selected seven bacteriophages for further characterization based on restriction enzyme digestion patterns of genomic DNA. Among the studied bacteriophages, two belong to the Myoviridae family and three belong to the Podoviridae family, based on morphology observed by transmission electron microscopy. The host range of the selected bacteriophages was confirmed using 18 strains of P. syringae pv. actinidiae, including the Psa2 and Psa3 groups, and some were also effective against other P. syringae pathovars. Lytic activity of the selected bacteriophages was sustained in vitro until 80 h, and their activity remained stable up to 50°C, at pH 11, and under UV-B light. These results indicate that the isolated bacteriophages are specific to P. syringae species and are resistant to various environmental factors, implying their potential use in control of bacterial canker disease in kiwifruits.

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Herbicide-tolerant Zoysia grass (Zoysia japonica Steud.) has been generated previously through Agrobacterium tumefaciens-mediated transformation. The genetically modified (GM) Zoysia grass survived Basta spraying and grew to maturity normally while the wild-type (WT) grass stopped growing and died. GM Zoysia grass will permit more efficient weed control for various turf grass plantings such as home lawns, golf courses, and parks. We examined the environmental/biodiversity risks of herbicide-tolerant GM Zoysia before applying to regulatory agencies for approval for commercial release. The GM and WT Zoysia grass' substantial trait equivalence, ability to cross-pollinate, and gene flow in confined and unconfined test fields were selectively analyzed for environmental/biodiversity effects. No difference between GM and WT Zoysia grass in substantial traits was found. To assess the potential for cross-pollination and gene flow, a non-selective herbicide, Basta, was used. Results showed that unintended cross-pollination with and gene flow from GM Zoysia grass were not detected in neighboring weed species examined, but were observed in WT Zoysia grass (on average, 6% at proximity, 1.2% at a distance of 0.5 m and 0.12% at a radius of 3 m, and 0% at distances over 3 m). On the basis of these initial studies, we conclude that the GM Zoysia grass generated in our laboratory and tested in the Nam Jeju County field does not appear to pose a significant risk when cultivated outside of test fields.

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Pseudomonas syringae pv. actinidiae strains, the causal agents of bacterial canker on kiwifruit, were isolated from Korea and Italy in 2011. Among 87 isolates, a total of six representative strains, three from Korea and three from Italy, were identified on the basis of biochemical and physiological tests. Identities were confirmed by PCR using P. syringae pv. actinidiae-specific primers PsaF1/R2, which amplified a 280-bp DNA fragment. The strains isolated from Korea in this study displayed BOX-PCR patterns similar to those isolated from Italy but different from those isolated previously in Korea or the pathotype P. syringae pv. actinidiae strain. The effector hopA1 and hopH1 genes, which are known to be present in strains isolated recently from France and Italy, were also present in P. syringae pv. actinidiae strains, SYS1, SYS2 and SYS4, isolated from Korea in this work. However, no amplicons of the expected size were obtained from strains previously isolated from Korea and Japan. In addition, the Korean strains isolated in this work belonged to haplotype I for the cts gene identical to those strains isolated from recent outbreaks in Italy. These results suggest that P. syringae pv. actinidiae strains isolated from Korea and examined in this work are a new type of strain similar to those found from recent outbreaks in Italy. This is the first report on the occurrence of cts haplotype I strains of P. syringae pv. actinidiae affecting kiwifruit plants in Korea.