Screening Of High And Low Cadmium Accumulation Triticum Aestivum Varieties And Research On The Difference And Mechanism Of Cadmium Absorption And Transport

Cadmium(Cd)is a toxic heavy metal element.The Cd exceeded the standard number of 7% in cultivated soil in China.At the same time,wheat is the second largest grain crop in China.Therefore,it is a great theoretical and practical significance to screen Wheat Cultivars with low Cd accumulation and identify their low accumulation physiology and molecular mechanism.The main wheat varieties collected throughout the country were used as materials.On the basis of the analysis of the difference of Cd content in different varieties of grain,the characteristics of molecular marker and ionomics of high and low accumulated wheat varieties were discussed.And the difference mechanism between high and low Cd accumulated varieties in the absorption and transport of Cd was further analyzed.The main results were as follows:1.Screening of high and low grain Cd accumulation varities.Through 2 years of field experiments,the Cd content in the grain of 134 Chinese wheat varieties was selected as the main index of Cd content in the mature period.15 high grain Cd accumulation varieties and 15 low grain Cd accumulation varieties were selected from 134 Chinese Wheat Varieties.2.Molecular marker characteristics of high and low Cd accumulation in wheat grain.The relationship between molecular marker(Usw47,Scopc20)and Cd content in wheat grain was analyzed.The results showed that the identification rate of high and low grain Cd accumulation wheat varieties was low by using Usw47 or Scopc20 markers alone.However,the identification rate of high and low grain Cd accumulation wheat varieties can be increased from 66.7% and 46.7% to 88.9% and 85.7% by using the method of Usw47 markers combined with the Cd migration coefficient at the seedling stage.3.Ionomic characteristics of high and low grain Cd accumulation varieties.The results of cluster analysis showed that the high grain Cd accumulation varieties could be divided into two categories: high accumulation of Cd and low accumulation of Cd in the glume.The low grain Cd accumulation varieties could be divided into two types: high accumulation of Cd in glume and high accumulation of Cd in stem.The accumulation of Cd in grain,glume and stem of wheat was closely related to zinc,calcium,magnesium and manganese.The content of Cd in grain of wheat was positively correlated with the content of zinc,calcium,magnesium,iron and manganese.Cd content in leaves was negatively correlated with zinc content.while Cd content in stem was negatively correlated with calcium and manganese content.There was a co-enrichment phenomenon between Cd and Zn in wheat grains,and both of them coincide with the equation of one and two order(R= 0.765,P<0.05).4.The difference mechanism of uptake and translocation of high and low grain Cd accumulation varieties.H86 had more developed roots and higher root TaIRT1 expression.And the Cd content of L15 in leaves and roots was lower than that of H86,and the distribution of Cd in the root cell wall and leaf vacuole of L15 was higher than that of H86,and the expression of TaHMA3 gene in each part of L15 was significantly higher than that of H86.It is inferred the weak Cd absorption and transport capacity of L15 which with low grain Cd content is weak,and more Cd regions are separated into the root cell wall and leaf vacuoles,which is the main cause of the low accumulation of Cd in grain.