Genetic Analysis Of Kernel Abortion In Vivo Haploid Induction And Research On The High Efficiency Automatic Sorting In Maize

Rapid and accurate sorting haploid kernels is a prerequisite for the largescale application of this technology.At present,the genes that induce haploid generation of male parent have been cloned,but the molecular basis and mechanism of maternal inducible and kernel abortion are still unclear.Haploid identification is an important in haploid breeding technology.At present,automatic sorting haploid kernel is mainly based on NMR single threshold methods.However,this system can’t sorting for embryo abortion kernels,which reduces sorting efficiency and increases sorting cost.The purpose of this study was to analyze the maternal genetic contribution to haploid production and to detected the QTL linked to maternal haploid inducible and kernel abortion by linkage analysis and GWAS.The method of morphology,cytology,molecular marker was analysis during induction of endosperm abortion kernel production,to reveal the haploid generation mechanism and induced haploid efficiency offers theoretical basis.To solve the embryo abortion kernel can’t be correct sorting problem,we first proposed that based on NMR double-threshold method of sorting haploid which provide the technical support for efficient automatic sorting.The main conclusions are as follows:1.23 inbred lines from five groups of germplasm and within the groups of inbred lines incomplete diallel cross 81 hybrids as the female materials,the inducer YHI-1 as male parent.The analysis results show that the HIR at Hainan and Change was 9.04%,6.33%.The results of heterosis index that 8 and 26 crosses were higher than that of the high-value parents under the two environments,and most of the crosses were mesophilic,but some of the crosses were lower than that of the low-value parents.The average heterosis index was 116.01 and 79.39%.2.We evaluated the haploid induction rate of different inducer line for two years,the results showed that there was a significant positive correlation between HIR and kernel abortion traits;The results of generalized heritability analysis showed that the heritability of En5thR,TEnAR and TAR was 93%,and the heritability of HIR was 86.14%.These inducers 809-3,810-7,811-1 were as high as 10%,among which the induction rate of 811-1 was as high as 15%.To provide excellent germplasm resources of haploid breeding.3.Two segregation population and a DH population were used to detect QTL associated with kernel abortions.A total of 62 QTL loci were identified between the two segregation populations,with contribution rates ranging from 3.27 to 14.7%.There were 5 overlapping regions between kernel abortion traits and induction rate traits.The chromosome bin 3.01-3.02,3.04-3.06,4.05-4.06,5.03-5.04,8.06 were QTL hotspots associated with 3 to 4 kernel abortion traits.There was a high positive correlation between the total abortion rate and haploid induction rate.The results of DH population showed that 5 QTL loci related to kernel abortion traits were detected,and the contribution rate varied from 6.37-16.11%.The QTL loci were mainly detected on chromosome 5,and the contribution rate was more than 10%.4.The associated population of 275 inbred lines was used as the maternal material,and the high-oil inducer line CAUHOI was as male.The number of different type of kernel abortion was counted.The HIR was calculated by sorting haploid with RI-nj marker and NMR sorting system.Based on the PCA+K general mixed linear model,109 SNPs were found to be significantly associated with kernel abortion traits in the two environments,including 67 SNPs in Hainan and 42 in Zhengzhou,these SNPs accounting for 12.04-20.02%of the phenotypic variation.A total of 55 candidate genes were found,48 had functional annotations.For maternal influence on in vivo haploid induction,three candidate genes.5.The inbred line CML134 and Zheng 58 were used as materials.Cytological morphology and molecular marker were used to detect the ear induced by CHOI2 and CAUHOI.The results showed that the kernel abortion was influenced by the male parent gametophyte.The endosperm abortion kernels were triploid by flow cytometry,the number of endosperms decreased.The partial deletion of radiation microtubules in early endosperm cells led to abnormal endosperm,the results of SSR molecular markers showed that there were male and female parent chromosome deletion in abortion kernel.It is suggested that the mechanism of haploid generation is related to the deletion of paternal chromosome to different degrees.6.Single kernel weight and oil content were measured for the diploid,haploid,and EmA kernels derived from three maize hybrids and nine inbred lines by in vivo induction.The results showed that the distribution of oil content showed defined boundaries between the three types of kernels,while the single kernel weight didn’t.According to the distribution of oil content in the three types of kernels,a doublethreshold method was proposed to distinguish the embryo-aborted kernels,haploid and diploid kernels based on NMR and their oil content.The double thresholds were set based on the minimum oil content of diploid kernels and the maximum content of EmA kernels as the upper and lower boundary values,respectively.The CDR of EmA kernels in different maize materials was>97.8%,and the average FDR was reduced by 27.9 percent.