| Mechanized kernel harvesting of maize?Zea mays L.?is the development trend of agricultural mechanization in our country.Kernel moisture content of maize at mature stage is an important trait in maize breeding and it is also a prerequisite for realizing mechanized degranulation and harvesting of maize.In this study,297 maize inbred lines were used as test materials,and we planted these meterials in two different locations for two years,the kernel moisture content and its related traits at mature stage were studied by drying method and moisture analyzer,and explore the method for rapid and non-destructive measurement of kernel moisture content in the field.Combined with 83,057 SNP markers obtained by GBS method in 248 maize inbred lines,the genome-wide association study?GWAS?of kernel moisture content related traits was used to screen the significant SNP loci associated with them,and then the candidate genes were exploited.The main findings were as follows:1.The parts related to the moisture content of mature maize kernels were screened:tassel stalks,loquat leaves and cobs.The results of two-point experiment in two years showed that there were extensive phenotypic variation in the moisture content of tassel stalks,the moisture content of loquat leaves,the moisture content of cobs and the moisture content of kernels in mature maize,and the generalized heritability was 48.65%70.03%.The generalized heritability was in turn the moisture content of tassel stalks,the moisture content of loquat leaves,the moisture content of kernels,and the moisture content of cobs.2.In four environments,a total of six inbred lines with a moisture content of less than 28%in maize were screened,which were LH162,NS501,L135,W117,LH127 and LH202,respectively.3.The BLUP values of the mature tassel stalk,loquat leave,cob and kernel moisture content measured by the drying method and the moisture analyzer were analyzed by T-test and correlation analysis.T-test and correlation analysis were carried out on the BLUP values of the tassel stalk,loquat leave,cob and kernel moisture content in mature period measured by drying method and moisture analyzer.It was found that the difference in moisture content measured by the two methods reached a very significant level,and there was a very significant positive correlation between them.The result indicated that the moisture content measured by the moisture analyzer and the actual moisture content of each part that could be reacted,and showed the feasibility of the application of the moisture analyzer used in this test in practice.4.In order to achieve the purpose of measuring the moisture content of mature maize kernels quickly,and non-destructive,a linear equation for calculating the moisture content of mature maize kernels was established:(4=-1.864+0.603(31+0.411(32(=3.92×10-12)((31,(32 indicated that the moisture analyzer measured the moisture content of the loquat leaves and the moisture content of the cob respectively;?4 indicated the moisture content of the kernel by the drying method?.5.The GWAS of the moisture content traits about the maize kernels and their related parts were carried out,and mapped a total of 96 trait-SNP loci?68 SNP loci were involved?,the phenotypic contribution rate was 0.19%46.78%.The trait-SNP loci associated with the moisture content of tassel stalks,the moisture content of loquat leaves,the moisture content of cobs and the moisture content of kernels were 16,36,28 and 16 respectively.The same traits co-localized to 15 co-sites in different environments,and 7 co-locations were co-located among different traits.6.The moisture content of the loquat leaves and cobs measured by the moisture analyzer was taken into the established linear equation to calculate the kernel moisture content,then GWAS was carried out,and a total of 13 SNP sites were mapped to the drying method.There were 5 identical sites in the locus associated with the kernel moisture content localized by the drying method.7.On the B73 AGPV2 reference genomic map of the maizeGDB website,23 candidate genes related to moisture content were found in the range of upstream and downstream 120kb of significant loci.In this study,the method of rapid and non-destructive for determining the moisture content of mature maize kernels by using the moisture analyzer was expiored,and a linear equation for the moisture content of maize kernels at maturity were established.Inbred lines with low kernel moisture content at mature stage were screened.Through the genome-wide association study,the SNP locus significantly correlated with kernel moisture content and related traits were detected,and the candidate genes were excavated,which provided the oretical guidance for molecular assisted breeding of maize kernel moisture content,and provided germplasm resources for maize seed harvesting. |
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