Study On The Characteristics Of The Grain Dehydration Of Maize Inbred Lines With Different Maturity

The research on the characteristics of grain dehydration of maize is the key to overcome the bottleneck of the whole process of mechanical maize harvest in my country.It is of great significance to study the grain dehydration characteristics of maize inbred lines with different maturity,to select the materials of maize inbred lines that meet the breeding objectives of our country,to dig out the gene resources related to grain dehydration,and to construct its regulatory metabolic network for solving the bottleneck problem of maize production and development in China and accelerating the breeding of high-quality maize varieties.In this study,eleven maize inbred lines with different maturity selected from Shaan A group and Shaan B group were used as test materials.According to the growth period and maturity of the materials,the pollination period was similar through reasonable staggered sowing to ensure that all materials were pollinated on the same day.The oven dried method and the electronic moisture meter method were used to continuously measure the grain moisture content at different stages of the grain development.And the speed types of the grain dehydration of eleven maize inbred lines were divided.The RNA-seq technology was used to sequence the transcriptome of two maize inbred line materials KB182 and KB020 with obvious dehydration differences at 7,14,21,28,35,42,49,and 56 days after pollination.And combined with the dynamic development process of seeds after pollination,the WGCNA method was used to explore the reasons for the difference in grain dehydration between the two maize inbred lines.The main results are as follows:1.The oven dried method is more accurate for measuring the grain moisture content of maize,and it is suitable for measuring the grain moisture content during the whole growth period.The electronic moisture meter method was significantly correlated with the oven dried method in the later stage of grain development(that is,35 days after pollination and after)(P < 0.05),and it can replace the oven dried method to measure the grain moisture content.2.The grain moisture content of maize inbred lines with different maturity decreased gradually with the grain development,and there were significant differences in the change of grain moisture content among different materials.The BLUP of the grain moisture content of all materials in two years was carried out Euclidean clustering.And it was found that the grain moisture content of early maturing materials KB182 and KA225 decreased faster than that of KB207;that of medium maturing material KB089 decreased faster than that of KA147 and XCA-1;that of late maturing materials KA105 and 91227 decreased faster than that of 2082,KA327 and KB020.3.In the process of grain development,the curves of 100 grain dry weight of maize inbred lines with different maturity showed "S" type growth,and the curve of grain filling rate showed a single peak change.The peak time of grain filling rate of different materials was not consistent,which was basically within 21-28 days.There were significant differences in 100 grain dry weight among inbred lines,years,sampling periods and interactions.Late maturing materials KA105 and 91227 had stable grain filling parameters in two years.And the time needed to reach the maximum grain filling rate was short,and the maximum grain filling rate and average grain filling rate were large.Dry matter of KA105 and 91227 could increase to a higher accumulation in a short time,and then the grain filling process could be completed quickly,leaving enough time for grain dehydration in later stage.4.Based on the grain moisture data of different sampling periods measured by the oven dried method,eleven maize inbred lines with different maturity were divided into different dehydration types by K-means cluster analysis.Among them,KB182 and KA225 belonged to the type of fast dehydration with early maturing,KB207 the type of slow dehydration with early maturing,KA105 and 91227 belonged to the type of fast dehydration with late maturing,KA327 and KB020 belonged to the type of slow dehydration with late maturing.5.Correlation analysis showed that the grain dehydration rate was significantly positively correlated with protein content,and negatively correlated with plant height,bract length,the moisture content of bract,ear length,ear diameter,grain length,grain width,grain thickness,crude fat and starch content to a certain extent.That is to say,the maize materials with fast grain dehydration and low grain moisture content at harvest generally showed the characteristics of the lower plant height,the shorter bract length,the lower moisture content of bract,the shorter ear length,the thinner ear diameter,the shorter grain length,the smaller grain width,the thinner grain thickness,the higher protein content and the lower crude fat and starch content.6.Analysis of the regulatory metabolic network of maize grain dehydration based on transcriptome sequencing.Transcriptome analysis was performed on the seeds of two maize inbred lines KB182 and KB020 with large differences of dehydration.The WGCNA method was used to construct a co-expression regulatory network for the grain moisture content,dehydration rate and AUDDC.It was found that there were six modules related to the grain moisture content,and four common modules were related to the dehydration rate and AUDDC.The core genes in these modules may be candidate genes related to grain dehydration of maize.Among them,the gene GRMZM2G137211(Zm00001d020929),which is significantly related to dehydration traits,has been verified by gene editing and proved to be a candidate gene for the main QTL controlling maize grain moisture.In summary,eleven inbred lines derived from Shaan A and Shaan B group were evaluated for grain dehydration,and the dehydration types of different inbred lines were identified in this study.At the same time,the transcriptome sequencing technology was used to explore the regulatory metabolic network of genes related to grain dehydration.The results of research provided important clues for elucidating the key regulatory mechanism and metabolic network of grain dehydration of maize,and also provided an effective reference for accelerating the breeding of maize varieties suitable for mechanical grain harvesting.