Genetic Analysis Of Spontaneous Haploid Genome Doubling Ability Of Haploid Tassel In Maize

Spontaneous haploid genome doubling of maize is a key factor to improve the breeding efficiency of double haploids,but the efficiency of spontaneous doubling of maize haploid tassel is much lower than that of female ears,so this study focused on the spontaneous doubling trait of maize haploid tassel.In this experiment,two inbred lines,Zheng 58 and B73,were used as parents to construct F_2:3haploid lineage,and a total of eight traits were investigated under the three environments,including tassel length,tassel primary branch number,tassel secondary branch number,tassel branch number,anther ratio,anther score,pollen ratio,and pollen score.QTL localization studies for the traits were conducted by the Inclusive Composite Interval Mapping（ICIM）method,and genomic selection was performed using the Ridge regression best linear unbiased prediction（RR-BLUP）model.The main findings were as follows:（1）The correlation analysis showed highly significant positive correlations among three traits,haploid tassel branching number,tassel primary branch number and tassel secondary branch number,and highly significant positive correlations among four traits,anther ratio,pollen score,pollen ratio and pollen score.The heritability of eight traits detected was greater than 0.80,which could indicate that the traits were strongly influenced by genetic factors.（2）A total of six QTL regulating haploid tassel length were detected in the three environments and combined environment,among which q TL4-1、q TL4-2 and q TL4-3 both were minor QTL.（3）A total of eight QTL for tassel primary branch number were localized in three environments and the combined environment,among which q TPBN1-2,q TPBN4-2,q TPBN4-1 and q TPBN5-1 both were minor QTL.Seven QTL for tassel secondary branch number of haploid were localized in three environments and combined environment,with PVE ranging from 5.28%to 7.58%,indicating that tassel secondary branch number of haploid was controlled by micro-effective polygenes simultaneously.Nine QTL for tassel branch number of haploid were detected in the three environments and combined environment,among which q TBN4-1 and q TBN4-2 were minor QTL.Tassel primary branch number,tassel secondary branch number,and tassel branch number,were found in the interval of chromosome 1 bin1.03-bin1.04,chromosome 3bin3.03,chromosome 4 bin4.05,and chromosome 5 bin5.02,with one-causal polymorphic loci.（4）Six haploid anther ratio QTL were localized in the three environments and combined environment.q AR4-1 with PVE of 11.99%in the HTB2 environment and 5.97%in the combined environment,indicating that the environment had a greater influence on the anther ratio phenotype controlled by this locus.The pollen score was localized to three QTL loci in the three environments and the combined environment,and the q AS5-1 and q AS5-2 both were minor QTL..（5）The pollen ratio in three environments and combined environment was localized to seven QTL.q AR4-1 had a PVE of 10.23%under HTB2 and 5.75%in the combined environment,indicating that this locus was more influenced by the environment in controlling pollen ratio.The pollen score was localized to four QTL under the three environments and combined environment,and there was no minor QTL locus,indicating that it was controlled by micro-effective polygenes.The anther and pollen traits were found in chromosome 2 bin 2.08,chromosome 3 bin 3.09,chromosome 4 bin 4.08 and chromosome 5 bin 5.05,with one-causal polymorphic loci.（6）The genomic selection results showed that the prediction accuracy of different reference population sizes was measured,and the relatively high prediction accuracy was achieved when the reference population accounted for 60%of the total.The prediction accuracy of different number of SNP markers was analyzed,and all of them showed relatively high prediction accuracy when the number of SNP markers was 500.