Difference In Cadmium Absorption And Accumulation Between Hybrid Rice Varieties

China,as a major agricultural country,is the main production areas and consumption market for rice.At present,the soil heavy metal pollution is one of the main environmental problems in China.With the characteristic of wide range of sources,accumulation,and degradation-resistant,heavy metal pollution posed a serious threat to the quality of farmland soil and affected the quality and safety of agricultural products and human health.However,due to the large population of our country but low land possession per capita,how to use available resources efficiently and the safe-production of agricultural products in mild contaminated farmland,which have become an urgent issue to be settled.At present stage,the cultivation of rice variety with high-production and low-Cd is one of the effective ways to ensure the safe-production of grain.Therefore,this study aimed to find the key factors which affect the absorption,translocation and accumulation of Cd in different rice varieties for providing technical support for the selection of rice varieties with high-production and low-Cd.A hydroponic experiment were conducted to investigate the feature of cadmium(Cd)stress(2 mg·L-1)on absorption,transferring and accumulation of Cd by six hybrid rice.Statistical differences analysis of index of correlation were explored to the relationship between the difference of Cd assimilation,accumulation and transferring of rice varieties and the relative quantitative expression of OsHMA3 gene.The main results were as follows:(1)There were difference of Cd absorption,transfer and accumulation at different growth stages in whole growing process of all rice varities.Cd content in different organs of all varieties followed the order of maturity stage>tillering stage>seedling stage.The transfer ability of Cd from root to aboveground parts during the tillering stage was stronger than that during the maturity stage.It showed that the tillering stage and the mature stage were the two key stages to controlling Cd absorption in rice.Cd content in different organs of all varieties followed the order of root>stem>leaf>brown rice.The root was the primary organs of the rice in Cd absorption and accumulation.In addition,Cd stress to a certain extent has affect the dry weight of crops to limiting the growth of rice.(2)There was different that,the expression of OsHMA3 gene among different rice varieties in the whole growth period.The responsiveness of rice varieties may be different to Cd stress.In the seedling stage,only the OsHMA3 gene expression of R03 cultivars was up-regulated.In the tillering stage,the OSHMA3 gene expression of most rice cultivars was up-regulated.In mature stage,the expression of OsHMA3 of most rice cultivars gene was down regulated.(3)There was no significant correlation between OsHMA3 gene expression and Cd content in different organs of rice during the whole growing period.The relative expression of OsHMA3 gene in shoot was barely correlation,which may not play its function of transport.It showed that the relative expression of OsHMA3 gene did not directly affect the content of Cd in each organ.There were difference of the relative expression of OsHMA3 gene in different organs at different growth stages in whole growing process of all rice varities.Only in the tillering stage,the root of the relative expression of OsHMA3 was significant correlated with Cd accumulation in root,which showed a significant negative correlation with the shoot Cd accumulation.It showed that the key period of OsHMA3 gene expression was tillering stage,and the expression of the gene made a large amount of Cd retained in the root and not transported to the ground.(4)In the early field experiment(natural condition),the selected 6 rice varieties had different absorption characteristics.In this experiment,6 rice cultivars under Cd stress were all over the standard.Possible without the addition of exogenous Cd stress conditions,the rice itself characteristics are the major factors on the accumulation of Cd in the grain,and the addition of exogenous Cd stress conditions and external Cd concentrations to regulate grain Cd accumulation of a key role.Selection and breeding of suitable rice varieties in different Cd polluted environment.In addition,it is also possible that the self absorption characteristics of hybrid rice varieties are not stable enough.Further study on the difference of Cd uptake in different rice cultivars.