Screening Of Low-cadmium Accumulation Tobacco Materials And Its Cadmium Accumulation Characteristics

The Cd-contaminated soils planted with tobacco pose great threat to the tobacco quality and production,thus further human health.The low-Cd accumulation tobacco cultivars demonstrate lower Cd accumulation in the leaves of tobacco.Therefore,screening and breeding low-Cd accumulation tobacco cultivars is a practical way beneficial for tobacco production.In this study,hydroponic and pot experiments were conducted to obtain low-Cd accumulation tobacco cultivars from 93 tobacco materials,and subsequently investigate the Cd accumulation characteristics of the low-Cd accumulation tobacco cultivars.The results were as follows.(1)At the resettling stage,the shoot growth of the 93 tobacco materials were inhibited obviously with the treatment of the 2 mg L-1 and 10 mg L-1 Cd.There was significant difference for tolerance index,Cd concentration and Cd accumulation among tobacco cultivars,with 2.08-6.27-times difference.According to the cluster analysis based on tolerance index and Cd concentration in shoots,7 low-Cd accumulation tobacco cultivars,4 middle-Cd accumulation tobacco cultivars and 10 high-Cd accumulation tobacco cultivars were obtained.In especial,Yunyan85,Zhongyan90,Cuibil,CF986,RG11,91-58#and 960116#were low-Cd accumulation tobacco cultivars under the treatment of the 2 mg L-1 and 10 mg L-1 Cd.(2)At the treatment of 2 mg kg-1 and 4 mg kg-1 Cd,a little difference was observed for the Cd tolerance index of the 21 tobacco leaves.There was significant difference for Cd concentration and Cd accumulation in leaves among the 21 tobacco materials at the vigorous growing stage,with 2.24-2.69-times difference.According to the cluster analysis based on Cd concentration in leaves,4 low-Cd accumulation tobacco cultivars,7 middle-Cd accumulation tobacco cultivars and 2 high-Cd accumulation tobacco cultivars were obtained.CF986,RG11,91-58#and 960116#were evaluated as low-Cd accumulation tobacco cultivars.Yuyan5 and MF2S were evaluated as high-Cd accumulation tobacco cultivars.With the treatment of 2 mg kg-1 and 4 mg kg-1 Cd,there were no difference for Cd tolerance index of the leaves between low-Cd accumulation tobacco cultivars and middle-Cd accumulation tobacco cultivars or high-Cd accumulation tobacco cultivars.The Cd concentrations and Cd accumulation in leaves of the low-Cd accumulation tobacco cultivars were 51.26%-83.99%of the middle-Cd accumulation tobacco cultivars and high-Cd accumulation tobacco cultivars.(3)The biomass of the low-Cd accumulation tobacco cultivars,RG11 and CF086,decreased with the increasing Cd concentrations in soils,while the Cd concentration and Cd accumulation in RG11 and CF086 showed an increasing trend.The Cd concentrations in different tissues of the low-Cd accumulation tobacco cultivars decreased with the growth stages.The maximum Cd accumulation rate in leaves of RG11 and CF086 were observed at the peak stage.The Cd concentrations and Cd accumulation in roots and stems of RG11 and CF086 were significantly greater than those of Yuyan5,while Cd concentrations,Cd accumulation and Cd accumulation rates were significantly lower than those of Yuyan5 among growth stages.Furthermore,Cd distribution in different parts of RG11 and CF986 were represented as follow:lower leaf>middle leaf>upper leaf>stem>root.Cd distribution rates in leaves of RG11 and CF986 were significantly lower than those of Yuyan5,while those in roots and stems of RG11 and CF986 were 1.49-2.30 times higher than those of Yuyan5.Compared with the high Cd accumulation tobacco cultivars,the low-Cd accumulation tobacco cultivars demonstrate greater Cd accumulation in roots and stems,while lower Cd accumulation in leaves.(4)The Cd concentrations in different Cd fractions and subcellular fractions in different tissues of RG11 and CF986 significantly increased with increasing Cd concentrations in soils.The ethanol extracted-Cd dominated the total Cd in roots and stems of RG11 and CF986,while the NaCl extracted-Cd dominated in leaves.The concentrations and percentages of strong mobility Cd in roots and stems of RG11 and CF986 were significantly lower than those of Yuyan5.However,the concentrations and percentages of poor mobility Cd were significantly higher than those of Yuyan5.The Cd concentrations of each fractions in the leaves of RG11 and CF986 were significantly lower than those of Yuyan5.Cd concentrations in soluble fractions of roots and stems contributed the most,followed by cell wall fraction and organelle fraction,Cd concentrations in cell wall of leaves contributed the most,followed by soluble fraction and organelle fraction.The Cd concentrations in soluble fraction of roots,and cell wall in roots and stems of RG11 and CF986 were significantly higher than those of Yuyan5,however the Cd concentration in subcellular fractions of leaves were significantly lower than those of Yuyan5.Compared with the high-Cd accumulation tobacco cultivars,the low-Cd accumulation tobacco cultivars presented poorer mobility of Cd in roots and stems,while stronger immobilization ability of cell wall,which may limit the transportation of Cd to the aboveground part,and unloading of Cd to the leaves.