| Mineral trace element is beneficial if it intaken in low amount in dietary, to some extent, affect the health of consumers. Rice is one of the major grain crops in China. Some important mineral trace elements in rice varieties introduced currently which are significantly less in human body required. It is necessary to improve appropriate rice varieties and breeding technology.The conventional methods for determination of mineral elements in rice gave precision results. However, these methods usually need expensive equipment, complex and long-period sample preparation. During breeding process, many single hybrid rice plant need to be screened out and identified within limited time. In most breeding cases, screening out the relative higher content mineral trace elements individual plant is difficult for the subsequent application of planting and further screening. Therefore, simple and efficient methods for determination of mineral trace elements are urgently needed, which can accelerate the cultivation, promotion and application of new functional rice varieties.Based on the actual situation of the selection of germplasm resources and individual-plant, five different types of rice varieties (lines), Jiayu 293, Heinuomi/Zhenong 80102, Zhenong 35, Zhenong 37 and Shengtai 1 were employed for comparison of three pretreatment methods:extraction by hydrochloric acid method, dry aching digestion method and wet digestion method. To further investigate the content of Zn, Mg and Ca, seven different types of rice varieties (lines), Jiayu 293, Shengtai 1, Zhenong 35, Zhewen 1, Jinzhong 1, Zhenong 934 and Fuxin 3 were employed in the present study. The high efficiency methods for determination of mineral trace elements in rice were optimized through the methods of extraction by hydrochloric acid, gelatinized brown rice, chromogenic reaction and the solution color contrast methods usedin this study. The rapid determination methods of brown rice and quantitative determination methods of brown rice flour were created, and they were employed in the selection of germplasm resources and individual-plant. The experiment results were as below:1. Compared with extraction by hydrochloric acid method, dry aching digestion method and wet digestion method, the contents of Zn, Mg and Ca in different treatments had some certain differences. The accuracy of the wet digestion method was the highest among the three pretreatment methods, the accuracy of the extraction by hydrochloric acid method was the lowest. The contents of Zn, Mg in the wet digestion method were the highest, while the content of Ca in the dry aching digestion method was the highest, but the contents of Zn, Mg and Ca by hydrochloric acid method were the lowest.2. We examined the contents of Zn, Mg and Ca of the grain by different milling degree. As a result, with the increase of degree of milling, the contents of Zn, Mg and Ca decreased with different degrees, but the distribution and content of Ca and Mg in the outer layer of rice were more obvious than that of Zn. The content of Ca among the tested varieties had the largest variation, the variation coefficients of Mg between varieties were lowest. With the increase of degree of milling, the variation coefficients of Zn and Ca between varieties decreased gradually, and the variation coefficients of Mg between varieties were little changed. Analysis of their distribution showed that Mg and Ca were mainly distributed in the outer fraction of rice, but the distribution of Zn was more uniform.3. The determination of content of Zn in brown rice flour Spectrophotometric method using BPT agent based on the extraction by hydrochloric acid method. The optimum analysis system was determined by optimizing the pretreatment method, masking agent, buffer solution, dosages of OP and the chromogenic agent. Beer’s law is obeyed in the Zn concentration range from 0 to 0.4 mg/L. The linear regression equation was y = 1.338x-0.061, where R2= 0.997. A method was proposed for the determination of Mg content in brown rice flour by spectrophotometric method used titan yellow as spectrophotometric agent based on the extraction by hydrochloric acid. The optimum analysis system was determined by optimizing the pretreatment method, masking agent, buffer solution, dosages of NaOH and the chromogenic agent. Beer’s law is obeyed in the Mg concentration range from 0 to 2.5 mg/L. The linear regression equation wasy= 0.089x+0.033, where R2= 0.999. The method was proposed for the determination of Ca content in brown rice flour spectrophotometric method using arsenazo III as spectrophotometric agent based on the extraction by hydrochloric acid. The optimum analysis system was determined by optimizing the pretreatment method, masking agent, buffer solution, buffer solution and dosages of the chromogenic agent. Beer’s law is obeyed in the Ca concentration range from 0 to 1.0 mg/L. The linear regression equation was y= 0.999.x+0.052, where R2= 0.999. These three methods were simple and effective, and which can meet the requirement for rice breeding.4. The rapid determination methods of brown rice grain were proposed. This method did not require the brown rice flour, qualitative selection using brown rice grain. The screening process of the samples can be completed within one day, and also can be screened more than 150-200 samples at the same time. They were employed in the selection of germplasm resources and individual-plant. New functional rice varieties rich in Zn, Mg and Ca can be obtained with higher efficiency.5.348 rice materials of different breeding generation were screened using the rapid determination methods of brown rice. The screened out number of high Zn, high Mg, high Ca materials were 15,27 and 34 respectively. The number of low Zn, low Mg, low Ca materials screened out were 15,16 and 15, respectively. After repeated validation and screening,11 new functional rice varieties (germplasm) with rich Zn, Ca and Mghave been obtained. These new functional rice germplasm or varieties (lines) might be further used in the production of rice or as the parent(s). In the course of screening, we found that Zn was correlated with Mg, and Zn and Ca were oppositely correlated. It was found that most of the high Ca materials are short grain type or medium grain type rice, indicated that Ca and grain length were positively correlated. Selection of long grain type rice in breeding practice can complete the indirect selection of the rice which rich in Ca. |
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