The Evaluation Of Germination Characteristics For Maize Inbred Lines Under Low Temperature And Genome-wide Association Study With SNP

Object: Low temperature in early spring heavily impact on seed emergence and seedling growth because of its longer duration.This also affects seedling morphogenesis and makes a reduction on maize yield.So,it has a significant value to study germination characteristics of maize inbred lines under low temperature,which can contribute to cultivate varieties that suit sowing in early spring.Methods: Used germination phenotypic traits of 209 maize inbred lines,the research expected to explore the diversity of seedling morphogenesis and established classified evaluation system of germination characteristics under low temperature.According to the system we set up,evaluated the diversity of germination characteristics of 209 maize inbred lines,and provided the basis for selecting that had a good behavior under low temperature.In addition,combined with the genome-wide association study,the research hoped to find the corresponding SNP and dig out remarkable allelic genes in germplasm resources of maize.The results laid the foundation of corn germplasm improvement and molecular marker assisted breeding.The main results and conclusions:1 Under the treatment of 12.5?,seedling dry root weight,dry shoot weight,dry seedling weight and root to shoot ratio of maize inbred lines used for temperature screening had the largest discrete degree,seedling was most sensitive to low temperature of 12.5?.The results showed that 12.5 was suitable to ?study seedling morphogenesis in maize inbred lines under low temperature.2 Under the low-temperature stress,dry shoot weight decreased by 75% on average,dry root weight decreased by 66% on average,dry seedling weight decreased by 71% on average.The rate of root to shoot increased by 29% compared with that under normal temperature,and which was 1.16 on average under the low temperature.The rate of root to shoot increased significantly,the growth of seedling root suffered lighter inhibition than seedling shoot,and shoot was more sensitive to low temperature than root.When root to shoot ratio were used as the index,the No.of maize inbred lines which were sensitive to low temperature were 79,and insensitive maize inbred lines were 6.3 The SNP chip with 56110 makers was used to test SNP locus of maize DNA.Eventually,35171 dependable SNP makers were selected out.The proportion of R2?0.33 was 20.19% in the number of paired SNP.LD in the population of genome-wide association study was high.The results showed that 209 maize inbred lines could be classified 4 group when SNP genetic polymorphism were used to estimate,they are TSPT(No.41),P(No.43),Reid(No.71)and others(No.54).4 The results showed that there was a negative correlation between the hundred-grain weight and the matter transformation ratio,the correlation coefficients was-0.49.The correlation of matter transformation ratio under normal temperature to that under low temperature were positive significant but not to Vitreous area ratio.5 The relative value of germination percentage,dry seedling weight and root length in 209 maize inbred lines under low and normal temperature were used to establish the evaluation system of the low-temperature germination.The system that range of standardized character value was took advantage of classified evaluation on low-temperature germination characteristics.The evaluation system of single index could be applied to evaluate on low temperature resistance expediently and accurately.6 SNP makers significant related to matter transformation ratio were 4,they were located in maize chromosome-cassette 3.05,4.03 and 10.04,and the last one had two SNP makers.The highest one could account for 13.62% of phenotypic variation.The relative value of germination percentage,dry seedling weight and root length with 35171 SNP makers were used to genome-wide association study,cold resistance SNP makers significant related to the relative value of germination percentage were 6(-log P>4),dry seedling weight were 4(-log P>4),and root length were 12(-log P>5).They were located in maize chromosome-cassette 2.04?3.03?3.04?3.05?5.04?3.09?4.05?7.01?7.02 and 8.02,the highest one could account for 13.62% of phenotypic variation.7 22 candidate genes were gained after blast with 22 SNP makers.The function of 22 candicate genes had 3 categories.9 took part in plant defense.6 were involved in material and energy metabolism.5 participated in signal transduction of plant.The functions of rest candicate genes were unknown.