Study On Absorption Characteristics And Seedling Stage Sensitivity Of Zhenghong Series New Maize Varieties (Combinations) To Heavy Metals

The southwest mountain maize region is the third largest maize producing region in China.The unit yield is lower than the national average level,the quality is poor,the contradiction between supply and demand is prominent,the production conditions are complex.And the production conditions in this region are complex and the soil heavy metal pollution is serious.It can be seen that it is very important to select and promote high yield,high quality and heavy metal pollution resistant maize hybrids.Therefore,this study mainly evaluated the application potential of 26 Zhenghong series new maize varieties（combinations）from the aspects of high yield,quality performance and heavy metal resistance,which has important practical guiding significance.At the same time,the study on the correlation between heavy metal pollution resistance of maize hybrids at seedling stage and heavy metal accumulation characteristics of grains can provide reference for heavy metal resistance breeding of maize.The main results are as follows:1.High yield performance of 26 new varieties（combinations）:the yield range of 26varieties（combinations）was 8074.79-10241.05 kg/hm²,11 varieties（combinations）with higher yield than CD30 and 17 varieties（combinations）with higher yield than ZD808.ZH909 and ZH985 were more than 10%higher than the two controls,and ZH989,ZH807,ZH622 were 5-10%higher than the two controls,indicating that they have outstanding high yield and great yield potential.2.Quality performance of 26 new varieties（combinations）:quality analysis showed that except ZH509,the grain volume weight of the other 25 varieties（combinations）exceeded the first-class standard of the national quality standard for maize（GB 1353-2018）.Among them,the grain volume weight of ZH909,ZH818 and ZH325 exceeded 780 g/L,and 8 varieties（combinations）such as ZH985 and GR006 exceeded 760 g/L.According to the grading standard of forage maize quality（GB/T 17890-2008 Forage Maize）,the forage quality of 26 new varieties（combinations）reached the first-class standard.Among the 26new varieties（combinations）,the volume weight of seven varieties（combinations）such as ZH818,ZH325 were significantly higher than the two controls,which fully showed that their comprehensive qualities such as commodity quality and forage quality are excellent.3.Performance of heavy metal content in grains of 26 new varieties（combinations）:referring to Limits of eight elements in cereals,legume,tubes and its products（NY861-2004）,among the 26 new maize varieties and 2control varieties,the excess limit rate of Cd in grains was 57.14%,the excess limit rate of Cr in grains was 3.57%,and the contents of Pb,Zn and Cu in grains were lower than the standard limit value.The combined pollution degree of heavy metals in maize varieties was calculated by the weighted comprehensive index method based on the improved AHP,and the cluster analysis was carried out according to the Euclidean distance and the sum of squares of deviations.The results showed that the variation range of the comprehensive pollution index of each variety（combination）was 0.235-3.218.Among them,the comprehensive pollution index of 12 varieties（combinations）such as ZH205,ZH447,GR563 and ZH325was relatively low,which was determined as class I pollution;In addition,except ZH510,the comprehensive pollution index of the other 25 varieties（combinations）were lower than CD30,and 21 varieties（combinations）such as ZH818 and ZH622 were lower than ZD808,indicating that their grains had low adsorption capacity for heavy metals.4.Heavy metal resistance of 26 new varieties（combinations）at seedling stage:this study analyzed the heavy metal resistance of 26 Zhenghong series new maize varieties（combinations）and 2 control varieties at seedling stage.The hydroponic experiment was carried out by adding Cd²⁺,Pb²⁺,Cr⁶⁺,Zn²⁺and Cu²⁺heavy metal solutions with a concentration of 100 mg/L respectively at the seedling stage for single stress treatment.11indexes such as plant height were investigated.The heavy metal resistance among them at seedling stage was analyzed by principal component analysis and membership function method.The main results were as follows:12 varieties（combinations）such as GR612 had strong Cd resistance;9 varieties（combinations）such as ZH510 had strong Pb resistance;ZH622,ZH09,GR612 and ZH412 have strong Cr resistance;9 varieties（combinations）such as ZH818 had strong Zn resistance;11 varieties（combinations）such as ZH509 had strong Cu resistance.By calculating the comprehensive evaluation value of the resistance of the tested varieties（combinations）to five kinds of heavy metals at seedling stage,and carrying out cluster analysis according to euclidean distance and sum of squares of deviation,they can be divided to four categories.Class I was the varieties（combinations）with strong resistance to heavy metals,including GR612 and ZH412;ClassⅡwas heavy metal resistant varieties（combinations）,including 13 varieties（combinations）such as ZH816;ClassⅢwas medium heavy metal resistant varieties（combinations）,including 5varieties（combinations）such as ZH510;ClassⅣwas heavy metal sensitive varieties（combinations）,including 8 varieties（combinations）such as GR563.In addition,26 new maize varieties（combinations）had better resistance to heavy metals at the seedling stage than ZD808,and 18 varieties（combinations）such as ZH909were better than CD30.5.Correlation between heavy metal resistance at seedling stage and grain heavy metal accumulation characteristics of maize varieties（combinations）:In this study,26 new maize varieties（combinations）of Zhenghong series and 2 control varieties were used as materials to analyze the correlation between the comprehensive pollution index of heavy metals in grains at maturity and the comprehensive evaluation value of resistance to heavy metals at seedling stage.The results showed that there was no obvious correlation between the comprehensive pollution index of grains at maturity and resistance to heavy metals at seedling stage.It is proved that the heavy metal absorption characteristics of grains at mature stage cannot be predicted simply based on the heavy metal resistance at seedling stage in breeding practice.6.Application potential of 26 new varieties（combinations）:according to the comprehensive analysis of high yield,quality performance and grain adsorption characteristics of heavy metals,9 new varieties（combinations）including ZH909,ZH807,ZH622,ZH841,ZH412,ZH325,ZH205,ZH435 and ZH447 have excellent performance,strong ecological adaptability,low adsorption of heavy metals and great comprehensive application potential.It is suggested to increase the research on their supporting cultivation techniques and gradually demonstrate and popularize them.In addition,GR006,ZH447,ZH807,ZH406,ZH325,ZH787 and GR563 are more sensitive to heavy metals at seedling stage.In production,it is necessary to avoid popularization and application in areas with serious heavy metal pollution,and strengthen field management at seedling stage.