Study On Cadmium Tolerance Charateristics Of Different Wheat Varieties And Selection For Low Accumulation Varieties

Cadmium(Od),as a heavy metal element with high mobility,has strong activity in the soil,and is easily transferred from the soil to the edible parts of crops,thereby affecting human health.One important measure to reduce the Cd content in crop grains is the screening for Cd low-accumulation varieties.Wheat is the staple food crop in the Huanghuaihai region of China.Studying the Cd tolerance characteristics of different wheat varieties and screening out low-accumulation Cd varieties have high practical value for food security.Thus,65 wheat varieties in Henan Province were selected to conducted hydroponic trial.Growth status,root morphology,Cd subcellular distribution and chemical form were determinated.In addition,field research using 30 wheat varieties was developed to screen for low-accumulation varieties.The results of this study are listed as follows:1.According to the evaluation of the modified membership function on Cd resistance,Cd resistance index of 65 varieties averaged 0.36.The strongest Cd tolerance was within variety 15.Eight varieties were more-resistant to Cd,such as variety 4,variety 20 and variety 16,etc;Eleven varieties were classified as Cd-sensitive,such as variety 61,variety 64 and variety 65,etc,Tolerance to Cd in variety 41 was the weakest.2.For Cd subcellular distribution in stems and leaves,Cd content in cell wall was the highest.Among these varieties,the Cd content in cell wall of stems and leaves in variety 27 was as high as 20.28 mg kg-1,accounting for 67.77%.The results showed that cell wall exhibited a fixation-effect on Cd,which could prevent Cd from entering cells and from producing a toxic effect.Unlike those in stems and leaves,Cd content in cytosol in roots was the highest.For.varieties studied,Cd content in cytosol in variety 48 was the highest,which was 108.61 mg kg-1 and accounting for 84.67%.It was indicated that there was Cd compartmentalization in the root cell.3.For chemical form of Cd in stems and leaves,the main form were sodium chloride extraction,followed by alcohol extraction Cd.Variety 50 had the highest Cd which was extracted by sodium chloride,i.e.18.98 mg kg-1m,which could accounting for 68.53%.This indicated that Cd in stems and leaves were mainly binded to pectin,protein.In roots,most Cd could be extracted by alcohol extraction.The highest value was obtained in variety 18,which could reach 80.17 mg kg-1,and occupy 66.98%.4.Field trial showed that Cd content of grains,stems,leaves and roots among different wheat varieties were significantly different.For the 30 wheat varieties concerned,the difference in Cd concentration in grains between the highest and lowest was 18.29 times.The grain Cd content of 9 varieties,such as variety D20,D28 and D4 were lower than the national food standard.Among these varieties,7 varieties were in the top-10 low shoot-content varieties.Grain Cd content had a significant positive correlation with the transfer coefficient TF grain/(stem and leaf)and with the enrichment coefficient BCF.The poor capability in Cd transport resulted in the low accumulation characteristics in wheat varieties.