Hyeong-Kwon Shim

Effects of Bacterial Leaf Blight Occurrence on Rice Yield and Grain Quality in Different Rice Growth Stage

We investigated the first symptom emerging date of rice bacterial leaf blight disease during four years from 2002 to 2005. The disease occurrence date was earlier 2030 days in 2005 than that of 2002. The damage in different rice growth stage by the bacterial disease on rice yield and grain quality in southern part of Korea was examined. The disease decreased rice yield following by increased infection rates. Slight loss in rice yield and brown head rice rate were observed at below 10% level of infected leaf area, while over 25% infected leaf area caused the significant decrease in rice yield and brown head rice rate. More than 50% of the infected leaf area rate caused 29% yield reduction in case of infection at panicle formation stage and 18% of brown head rice rate. Cooked rice quality was also affected in the diseased rice by damage in palatability score and viscosity.

Measurement of Density for Xanthomoanas oryzae pv. oryzae Cell Using Real Time PCR

We developed a new measurement method for the density of Xanthomonas oryzae pv. oryzae(Xoo), a casual pathogen of bacterial leaf blight of rice. The new method used real time PCR with the highly characterized and specific Xan_PahgeF & Xan_PahgeR primer and Xan_Pahge FAM MGB probe primer pairs derived from phage-related integrase gene. The method was effective when tested with a variety of templates including isolated Xoo DNA, pure colonies or liquid culture sources, and could also work on contaminating water. A main advantage of this assay is to accurately and rapidly quantitate the population density of Xoo in paddy field water containing inhibitors.

Overwintering Site and Occurrence Dynamics of Scrobipalpa salinella (Zeller) (Lepidoptera: Gelechiidae)

The moving period and overwinteing site of Scrobipalpa salinella (Zeller) were investigated in Gimje, Jeonbuk, and Shinan, Jeonnam in the glasswort field. Densities of Scrobipalpa salinella larvae were started to increase from mid-September in halophytes, such as Suaeda asparagoides, S. japonica, and S. maritima, rather than glasswort. S. salinella was overwintering inside the halophytes in old larva. Density ratio of overwintering S. salinella in Suaeda asparagoides, S. japonica, and S. maritima were 20.5, 28.4 and 51.1%, respectively. Overwintering population was highest in S. maritima among halophytes. The occurrence of first adult in the next spring was from April 19 to April 20 in Gimje, Jeonbuk, and Shinan, Jeonnam.

Disease Incidence, Yield and Quality Comparisons among Rice Varieties with Different Resistance to Bacterial Leaf Blight

The influence of rice bacterial leaf blight (BLB) disease incidence on yield and quality of Nampyung, Gang-baek and Iksan493 was investigated in three areas, Gimje, Yeongam and Jangheung, frequently found BLB infested rice. The infection rate of Nampyung, susceptible to BLB disease, was higher () than Gang-baek () and Iksan493 (), have resistant gene Xa7 and xa5, respectively. BLB disease incidence was severely found in Gimj and then yield of Nampyung was reduced 65% (352 kg/10a) compared to Iksan493 (540 kg/10a) due to the decrease in the ripen grain filling, brown/rough ratio and 1,000 grain weight. There was no difference of rice yield among Nampyung, Gangbaek and Iksan493 in Yeongam and Jangheung. The occurrence time of disease in Yeongam and Jangheung was later than Gimje and BLB disease was less infected in these areas. BLB infected rice grain showed inferior grain appearance and taste index to sound grain. independent of rice with resistant gene. In Yeongam and Jangheung, Gangbaek and Iksan493 cultivated showed lower ratio of white color to belly than Nampyung. Iksan493 showed better grain appearance and lower ratio of white core to belly than Gangbaek. In protein content of rice grain, the range of Gangbaek and Iksan493 was , but Nampyung showed unstable ranged from undetermined to 9.0%.

Cultural and Rainfall Factors Involved in Disease Development of Fusarium Wilt of Sweet Potato

Environmental factors such as soil moisture, land management, and weather conditions affecting Fusarium wilt of sweet potato were investigated in major sweet potato cultivation regions in Korea. Fusarium wilt occurred mainly in reclaimed terracing lands, which are flattened and located in hilly to mountainous areas at the base of the mountain, in early seasonal cultivation regions. Disease severity was lower in reclaimed fields with natural slope. The development of Fusarium wilt in the fields was highly correlated with precipitation during planting period (r