Inn-Shik Myung

Review of Disease Incidences of Major Crops of the South Korea in 2005

In 2004, average temperature was higher, and rainfall was less than those of previous year, The diseases of rice, barley, pepper, chinese melon, apple and oriental pear were surveyed. Seedling diseases, leaf blast, sheath blight and bacterial blight of rice, phytophthova blight, virus diseases and anthracnose of pepper, and sudden wilt syndrome and powdery mildew of chinese melon grown in plastic greenhouse were severe. Especially, sheath blight and bacterial blight of rice occurred two times higher than those of previous year, Panicle blight of rice decreased about 4 times, compared with the previous year, presumed that the lower rainy days, rainfall and RH suppressed spread of the fungal pathogens to panicles of rice. Lower rainfall during mid- and late Aug caused three-times less occurrence of phytophtora blight of red-pepper than that of the previous year, Another diseases surveyed occurred similar or less than those of the previous year.

Development of In Vitro Seedling Screening Method for Selection of Resistant Rice Against Bakanae Disease

Rice bakanae disease, caused by the fungus Fusarium fujikuroi, is one of the most important rice diseases and distributed widely in Asia. Resistance screening system in rice field had been established. However, the evaluation results of the system vary according to the environmental conditions when the test is conducted. To develop precise and rapid evaluation method of disease resistance of rice to bakanae disease, in vitro screening system was attempted in this study. The six cultivars namely, `Nampyeongbyeo`, `Junambyeo`, `Chucheongbyeo`, `Samcheonbyeo`, `Odaebyeo` and `Hwasinbyeo` were tested. They were planted onto MS agar medium (10 ml) in test tube () and incubated at and in growth chamber under 12 hr light condition. Symptoms of over growth appeared a few days after seeding and then seedling were withered 2-3 weeks after over growth. The disease symptoms such as leaf dryness on top of rice were appeared in the `Nampyeongbyeo` from 28 days at the concentration of spores/ml culturing at and then withered completely 35 days after seeding. Whereas the other varieties withered entirely 19-23 days after seeding. Using the in vitro seedling screening method, 72 rice varieties were investigated to select resistant cultivar. Finally, two resistant cultivars (`Nampyeongbyeo` and `Inwolbyeo`) and seven moderately resistant cultivars (`Hwadongbyeo`, `Seokjeongbyeo`, `Samgwangbyeo`, `Sampyeongbyeo`, `Nonghobyeo`, `Heukjinjubyeo` and, `Joanbyeo`) were selected. If in vitro seedling screening method was used for evaluation of bakanae disease resistance, it would be completed within 35 days after sowing of rice seed.

Survey of Major Disease Incidence of Rice in Korea during 1999-2008

During the period from 1999 to 2008, we surveyed the major diseases incidence of rice in Korea. Leaf blast showed 0.85% of the diseased leaf area in 2000 and then consistently decreased to 0.02% by 2008. However, panicle blast irregularly appeared by the years depending on weather conditions for disease development from heading to milk stage of rice. Diseased lesion height of sheath blight had the lowest (10.1%) incidence in 2001 and the highest (21.4%) incidence in 2007. A negative corelation (

Bacterial Blight of Shallot, Caused by Pseudomonas syringae pv. porri, a New Disease in Korea

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Evaluation of Shiranuhi, a Hybrid of Kiyomi Tangor and Nakano No.3 Ponkan, for Resistance to Citrus Canker in Growth Chamber

Shallots (Allium cepa var. ascalonicum L.) affected by bacterialblight disease received for diagnosis in March 2007 (Fig. 1A).Grower has estimated and we have confirmed that as much as two-third of the plant was affected by the disease in fields in the DaejungDistrict, Seokwipo of Jeju, Korea in April, 2007. The symptoms onleaves included yellowish and brownish leaf blight on leaf surface.Seriously infected plants shriveled and died in fields. Two isolates,BC2489 and BC2498 were recovered on trypticase soy agar (TSA)from symptomatic leaves of the plants. Pathogenicity was evaluatedon seven-week-old shallots by spot and spray inoculation. Bacteriawere grown on TSA for 48 h at 28

Evaluation of Potential of Mandarin Hybrid `Shiranuhi` against inoculation of Bacterial Canker Disease Pathogen (Xanthomonas axonopodis pv. citri) in Citrus Field in Jeju Island

Citrus canker disease is caused by bacteria Xanthomonas axonopodis .pv. Citri. Shiranuhi cultivar, a hybrid of Kiyomi tangor and Nakano No.3 ponkan was evaluated for resistance to citrus canker based on initiation of disease, percent area of lesion infected and growth rate of bacteria in the leaf under growth chamber condition. Significant differences between susceptible plant and resistant plants were observed in these assays. Resistant plants showed delayed disease symptoms compared to the susceptible plants after spray inoculation of the pathogen. The resistant verities, satsuma, yuzu, and Shiranuhi showed symptoms after six days where as susceptible, mexican lime showed the symptoms just after three days of inoculation. 18 days after inoculation, percent area of lesions developed on leaf and disease severity differed significantly in susceptible and resistant plants, and were ranked as follows: mexican lime > early satsuma

Dispersal of Citrus Bacterial Canker Caused by Xanthomonas axonopodis pv. citri in Nursery Plots of Unshiu Orange

This study was carried out to evaluate potential of Shiranuhi cultivar against inoculation of causal pathogen of citrus canker, Xanthomonas axonopodis pv. citri in Jeju Island by comparing degree of susceptibility of fruits and leaves/twigs, and analysis of incidence of canker disease. Progression of symptom, disease incidence, and percent area of lesion were surveyed for evaluation of resistance. In greenhouse condition, symptoms of bacterial citrus canker progressed more rapidly in sweet orange, a moderately susceptible cultivar, than in other four cultivars (satsuma mandarin, `Kiyomi`, `Shiranuhi` and `Yuzu`). At 20 days after inoculation, disease severity was the highest in sweet orange (5.00.0), and all tested leaves were distorted or had dropped. On the other hand, `Yuzu` showed the lowest disease severity (2.60.47), followed by `Kiyomi` (4.00.0), `Shiranuhi` (4.00.82), and satsuma mandarin (4.30.47). Percent area of lesion per leaf 30 days after inoculation was the highest in sweet orange (8.311.78), followed by satsuma mandarin (1.511.25), `Shiranuhi` (1.390.94), and `Kiyomi` (1.10.9), while the lowest was in `Yuzu` (0.260.17). Infield condition, percentage of diseased leaf in `Shiranuhi` was very low, 5.22.9, compared with sweet orange, 71.0 11.5, while that of satsuma mandarin and `Kiyomi` were 6.97.0 and 4.32.0, respectively. Percentages of diseased leaf was higher (17.47.1) than that of diseased fruit (3.22.5) in severely diseased trees of Shiranuhi cultivar, and the disease was not observed on twig in open field condition. Lesion sizes on leaves and fruits in open field condition were 4.12.2 mm2 and 5.15.6 mm2, respectively, while those in greenhouse condition were 8.75.7 mm2, 10.49.2 mm2 and 5.62.6 mm2 on leaves, fruits and twigs, respectively. The disease was observed in 5.6% out of total 107 farmers Shiranuhi fields under polyethylene film house, and average percentages of diseased tree in 31 fields of Shiranuhi cultivar and adjacent satsuma mandarin fields were 0.02% and 14.8%, respectively. Average percentage of diseased fruit was 1.6% in satsuma mandarin which was not observed in anyone of all the 31 Shiranuhi farmers fields. Therefore, it was concluded that `Shiranuhi` cultivar is not potential against causal pathogen of citrus canker disease in Jeju Island because the cultivar has similar resistance as satsuma mandarin which occupies over 95% of total 25,000 ha in Jeju Island in polyethylene film houses protected from outside.

Establishment of Economic Threshold by Evaluation of Yield Component and Yield Damages Caused by Leaf Spot Disease of Soybean

Dispersal of citrus bacterial canker caused by Xanthomonas axonopodis pv. citri on Unshiu orange was investigated in naturally infested nursery plot at Seogwipo in Jeju island, Korea. Based on phage detection, over 2% of the bacterial pathogen over-wintered in canker lesions and started to multiply in late May. However, symptoms were first observed 1 month after the phage detection. The disease dispersed non-directionally to nearby plants possibly because of indirect dissemination of the bacterium by rain splashes. The disease increased from late June to late August and decreased thereafter. Population of phage increased constantly, however, disease occurrence somewhat fluctuated due to environmental factors. Disease incidence and severity were correlated with rainfall with wind that occurred 14-32 days earlier from late May to late August.

Pathogenic Races of Pyricularia oryzae Isolated from Various Rice Cultivars on the Blast Nursery and Paddy Field in Different Locations

This study was carried out to investigate yield loss due to soybean leaf spot disease caused by Cercospora sojina Hara and to determine the economic threshold level. The investigations revealed highly significant correlations between disease severity (diseased leaf area) and yield components (pod number per plant, total grain number per plant, total grain weight per plant, percent of ripened grain, weight of hundred seed, and yield). The correlation coefficients between leaf spot severity and each component were �0.90, �0.90, �0.92, �0.99, �0.90 and �0.94, respectively. The yield was inversely proportional to the diseased leaf area increased. The regression equation, yield prediction model, between disease severity (x) and yield (y) was obtained as y= �3.7213x + 354.99 (R 2 = 0.9047). Based on the yield prediction model, economic injury level and economic threshold level could be set as 3.3% and 2.6% of diseased leaf area of soybean.

Crown Gall of Weeping Fig Caused by Agrobacterium larrymoorei and A. tumefaciens

Coordination Division, Research Policy Bureau, Rural Development Administration, Suwon 441-707, Korea(Received on August 27, 2012; Revised on November 30, 2012; Accepted on December 7, 2012)This study was conducted to investigate the association of race distribution of Pyricularia oryzae with ricecultivar and location. Races present in a given location were different in cultivars, and the races from a givencultivars were different by location. For precise study of race distribution, it needs to identify isolates byconsidering cultivation ratio and collection area. There are great differences between the resistant degree inthe upland blast nursery and on the resistant degree of the leaf blast and panical blast in the paddy field. Thenumber of virulent races in a rice cultivar was not related with the resistant degree in blast nursery or inpaddy field.Keywords : Pyricularia oryzae, Race, Rice blast