Screening Of Sweet Sorghum Germplasm Resistant To Petroleum Hydrocarbon Pollution And Its Responses To Phenanthrene Stress

Petroleum hydrocarbon pollutants have a high environmental risk.It is of great significance to control petroleum-contaminated soil to ensure the safe production of agricultural products and human health.Using energy plants to repair oil-contaminated salinized soil conforms to a principle that not competing with people for food and not competing with grain for land,and can benefit from remediation at the same time,opening up a new way for the treatment and rational use of contaminated soil In this study,a typical energy plant species,sweet sorghum（Sorghum bicolor）was used as material,and pot experiments were conducted to screen the varieties resistant to petroleum in salinized soil to evaluate its potential for remediation of petroleum-contaminated saline soil.In addition,physiological and metabolic response characteristics of S.bicolor to phenanthrene was comprehensively studied.The results are as follows:（1）Emergence rate,plant height and biomass of different varieties were measured to explore the performances of plants under petroleum pollution and the degradation of petroleum hydrocarbons in soil with candidate varieties were also studied.The results showed that the emergence of 24 of the 28 varieties were not reduced by the addition of 10 g/kg petroleum in soils with salinity of 0.31%.After a 40-day treatment in salinized soil with petroleum additions of 10 g/kg,4 potential well-performed varieties including ZK438,KT24,KT21 and KT6 with plant height of>40 cm and dry weight of>4 g were screened.Obvious degradation of petroleum hydrocarbons in the salinized soils planting the 4 varieties were observed.Compared with the treatment without plants,the residual petroleum hydrocarbon in soils planting KT21 decreased by 69.3%,46.3%,56.5%,50.9%and 41.4%,for the additions of 0,5,10,15 and 20 g/kg,respectively.In general,KT21 had the best performance and application potential to remediate petroleum-polluted salinized soil.（2）The physiological and biochemical response of KT21 to phenanthrene and associated degradation of phenanthrene were studied by hydroponic experiment.The results showed that the phenanthrene additions of 30 mg/L and 100 mg/L could significantly reduce the plant height,plant fresh weight,SPAD value and inhibit root growth of KT21 but would not cause significant effect on the SPAD value of KT21.Compared with the blank treatment with no phenanthrene added,phenanthrene-added treatments（30 mg/Land100 mg/L）did not affect（P>0.05）the indexes includinginitial Fluorescence origin,（Fo）,Fluorescence Photochemical quenchin（q ^P）and Non-photochemical quenching（NPQ）values of KT21 but significantly changed（P<0.05）those parameters including maximum photochemical efficiency（Fv/Fm）,actual photochemical efficiency（ΦPSII）and Photosynthetic electron transport rate（ETR）.The Fv/Fm,ΦPSII,ETR and q ^Pof KT21 seedlings of sweet sorghum showed a downward trend with the increase of phenanthrene concentration after phenanthrene treatment.The addition of 30 mg/L of phenanthrene significantly increased the contents of O₂^-and H₂O₂and the activity of Superoxide dismutase（SOD）in KT21.KT21 was stressed by 1mg/L of phenanthrene,but no obvious toxic symptoms was observed.The phenanthrene degradation rate,leaf and root enrichment coefficient of KT21 were significantly higher than those of 100mg/L phenanthrene treatment at 30 mg/L phenanthrene treatment,indicating that KT21 could better adapt to and degrade pollutants at low concentrations of pollution.（3）The key metabolites and metabolic pathways of phenanthrene were analyzed by metabolomics to explore the metabolic response of KT21 to typical petroleum hydrocarbon species.The stability and repeatability of metabolites in each group were high,the data were reliable,and the expression of metabolites was significantly different.The key metabolic pathway of phenanthrene involving the PAHs degradation pathway and benzoate degradation was detected in the underground part rather than in the aboveground part and the control group.After phenanthrene exposure,The degradation and metabolism of exogenous substances,energy metabolism,lipid metabolism,nucleotide metabolism,carbohydrate metabolism,amino acid metabolism,cofactor and vitamin metabolism,biosynthesis of other secondary metabolites,other amino acid metabolism and other metabolic pathways are active It is beneficial for KT21 to better adapt to phenanthrene stress.