Objective of this study was to investigate the residual levels of heavy metals in rice contract farming complex for exporting to China. Paddy soil, irrigation water and rice grain were taken from 20 fie1ds located in Icheon city, Cheorwon-gun, Cheongju city, Seocheon-gun, Gunsan city and Haenamgun. The elements of samples were analyzed using ion chromatography, ICP-OES, and ICP-MS after acid digestion. The arsenic (As) contents of paddy soil were ranged from 2.9 to 18.2 mg/kg, which were lower than 25 mg/kg as concern level of environmental pollution in Korea. Cadmium (Cd) was below the limit of quantitation (0.006 mg/kg) in all samples. The highest contents of copper (Cu) was detected to be 25.6 mg/kg in Seocheon-gun sample, but it was below 1/10 fold of the threshold levels 250 mg/kg for soil pollution. Also, the average contents of nikel (Ni), lead (Pb), zinc (Zn), and hexavalent chrome (Cr6+) were found to be lower than the criterion of soil pollution concern, and it was considered to be safe. The residual levels of arsenic in agricultural waters were relatively high, up to 24.3 ug/L in river water, but was detected as 1~2 ug/L level in the ground water. These levels are lower than the water quality standard, 0.05 mg/kg of agricultural water. The concentrations of mercury (Hg) and total chromium (Cr) in the white rice and brown rice were less than the limit of quantitation, and the levels of cadmium in the range of 0.004 to 0.068 mg/kg were less than safety criteria 0.2 mg/kg in Korea and China. In addition, the contents of lead (Pb) in white rice ranged from 0.002 to 0.136 mg/kg, which was safe to be 0.2 mg/kg for Korean white rice and 0.2 mg/kg for China brown rice. As a whole, the residual levels of heavy metals such as arsenic in rice was safely maintained as 1/10 to 1/20 of the residual limits of Korea and China. In conclusion, the heavy metals levels should not be worried in rice contract farming complex for exporting to China.

Sesame is queen of oil seed crops and widely cultivated in Asia and Africa. The aim of this study was to develop a mini sub core set representing the diverse germplasm of sesame and to assess the genetic diversity, population structure and phylogenetic relationship of the resulted sub core set to be used in whole genome resequencing platform. One hundred twelve accessions out of 277 accessions were selected by the PowerCore program. A total of 155 alleles were captured from the 158 alleles detected in the primary core population, and rare alleles and specific alleles were also maintained in the sub core set accessions representing almost 100% of the primary core population. Among the sub core set accessions, four sub populations were observed with some admixture accessions. Although the genetic diversity of Pop-1 which includes most accessions from Korea is relatively lower than that of other three sub populations, it can maintain maximum number of accessions in the sub core set with the same percentage as in the primary core set probably because of the specific features of these accessions. Based on this framework of genetically defined populations, the effective use and conservation management of Sesamum indicum for crop improvement might be possible.