Abstract: 【Objective】 In order to determine wheat grain selenium content in different wheat production regions in China, and to investigate factors that influence grain selenium content and agronomic measures that could increase selenium content, a wheat grain sampling and investigation and then a field experiment of foliar-selenium application on wheat were conducted.【Method】A total of 655 field wheat grain samples including 73 spring wheat and 582 winter wheat samples from different wheat production regions in China were collected from 2008-2009, 2009-2010, and 2010-2011 wheat seasons, and grain yield was investigated and grain selenium content was measured. The field experiment was conducted in 30 comprehensive experimental stations of China Agricultural Research System on Wheat in 14 provinces (municipalities) from 2010 to 2011, including two treatments of foliar applied with water and 0.017% sodium selenite solution at the middle and late jointing stages in a randomized complete block design with 3 replicates, and selenium content of plant before jointing and grain yield and selenium content at harvest were measured. 【Result】Over the 655 wheat grain samples, the average selenium content was 64.6 µg·kg^-1, which was too low to meet the selenium requirement of populations who rely primarily on wheat-derived foods, and grain selenium content ranged from 0 to 821.0 µg·kg^-1, with the average of spring and winter wheat of 67.5 and 64.2 µg·kg^-1. Of these samples, 63%, 19% and 8% had selenium content be deficient, low and enriched, no sample was found to have selenium content reach the toxic level. Selenium of wheat grain in different regions exhibited higher content in northern regions than that in southern regions, while it was higher in western regions than in eastern regions. Results from the field experiments showed that foliar application of sodium selenite did not significantly affect wheat grain yield, with yield for no selenium application and foliar selenium application averaged 6 650 and 6 649 kg·hm^-2. Foliar selenium application significantly increased grain selenium content, when no selenium was applied, grain selenium content averaged 31.0 µg·kg^-1, applying selenium at 116 g·hm^-2 increased the grain selenium content to an average of 647.8 µg·kg^-1, which reached selenium-enriched level, but still below toxic level. For 1.0 g Se·hm^-2 applied, grain selenium content was increased by an average of 5.3 µg·kg^-1, and applying 51 g Se·hm^-2 could increase the selenium content of wheat grain from the average of 31.0 µg·kg^-1 to above 300 µg·kg^-1. Grain selenium content was not influenced by yield, but under no selenium applied it was significantly correlated with the available soil selenium content in 0-20 cm soil layer and with selenium content of plant before jointing. For each 1.0 µg·kg^-1 increment of available soil selenium content from 6.3 to 30.7 µg·kg^-1, the grain selenium content without selenium applied increased by an average of 2.1 µg·kg^-1, and for each 1.0 µg·kg^-1 increment of selenium content of plant before jointing from 0 to 147.2 µg·kg^-1, the grain selenium content without selenium applied increased by an average of 0.7 µg·kg^-1. Grain selenium content with selenium applied as well as selenium biofortification index were both significantly correlated with selenium content of plant before jointing. For each 1.0 µg·kg^-1 increment of selenium content of plant before jointing, the grain selenium content with selenium applied increased by an average of 5.7 µg·kg^-1, and selenium biofortification index increased by an average of 0.043 μg·kg^-1(g·hm^-2)^-1. 【Conclusion】In agriculture production, applying selenium in soil before wheat jointing to increase the available soil selenium level, or applying foliar selenium fertilizer at the middle or the late jointing stage etc., are all effective measures to make the plant accumulate more selenium and to transfer it into grain at filling stage, and therefore increase the grain selenium content.

Key words: wheat, selenium, grain, soil