The Study For Haploid Male Fertility Of In Vivo Induction In Maize (Zea May. L)

Large-scale applications of DH breeding require breeders to do systematic research on every step during the process. Haploid induction and identification are not a big problem right now, but haploid doubling techniques are still not efficient enough to meet the high throughput production for DH lines, spontaneous doubling is one of the most convenient ways in DH breeding, however, the rate is so high. Therefore it is necessary to study the genetic characteristics and related genes of haploid male fertility (HMF) in order to explore new ways to increase spontaneous doubling rate. The main results are as follows:(1) This study classified the characteristics of HMF into different levels according to different haploid diploidization with different index:anther ratio, pollen ratio, anther score and pollen score were used to describe HMF. Haploids derived from16elite inbred and composed23F1hybrids covering the five heterotic groups were investigated of HMF in different environment in two years. It was found that haploid male fertility was mainly controlled by genetic background; the heritability of all of the traits was more than60%except that pollen score was a little lower and affected by the environment.(2) Cluster analysis found that the haploids originated from inbred lines Yu8701and4F1had better HMF capabilities than other materials, the fertile ratio was more than80%and90%of the fertile haploids were with high level. Xu178-derived haploids and Qi319-derived haploids performed well in anther traits; K22-derived haploids and B73-derived haploids performed well in pollen traits. The haploids from the hybrids of Yu8701always performed well in HMF but no same results were found in the haploids from the hybrids of4F1, which meant that there were more positive HMF related genes in Yu8701. Transgressive inheritance was found in the progeny of two low-frequency HMF inbred lines Chang7-2and Zheng58, which indicated that the trait could be improved through selection.(3) Other genetic factors of HMF were also investigated and found that HMF was mainly controlled by gene in nuclear, not in the cytoplasm. Inducer lines did not affect HMF.(4) Ploidy investigation of the leaf in pollination using flow cytometry found only10%high level fertile haploids contained half of the proportion of diploid cells, vegetative organs of most fertile haploids remained in the state of haploid, indicating that the reproductive cells should be doubled earlier than the vegetative cells.(5) A mapping population consisting of186F23family lines derived from the cross between Zheng58and Chang7-2was used to map the maternal QTL of in vivo haploid induction. Two quantitative trait loci (QTLs), qmhirl and qmhir2, were detected on chromosomes1and3and could be explained14.70%and8.42%of the phenotypic variation, respectively. This Zhengdan958F2:3population was also used to locate the HMF related genes. A total of8HMF related genes were detected. The loci on chromosome8qHmf7were detected in two replications; the loci qHmf5on3.07were verified in other genetic background Yu8701×Zheng58and4F1×Zheng58with extreme value chi-square test methods. Each of the contribution of these two loci was about10%. The predicted candidate gene was found to have different functions.(6) Early doubled haploid (EH) in haploid populations was studied systematically. Phenotypic characteristics analysis found that EH0performed better than normal doubled haploid in diploidizaion with totally fertile. Agronomic traits of the EH plants consistent with the inbred lines. SSR marker and SNP detections found that genotype of EH0was the same with the donor parents, EH is a kind of special DH from haploid spontaneous doubling in embryo development. The ratio of EH is about3%in haploid population.