Fine Mapping Haploid Induction Rate Gene Qhir1and Marker Assisted Selection Of Qhir1in Haploid Breeding In Maize

Doubled haploid (DH) technology is one of the key technologies in modern maize breeding. It is important for DH technology that inducers with high Haploid induction rate (HIR) and efficient haploid identification system. Phenotype selection was the major method to develop inducers with low efficient, new method for developing inducers should be improved. And it is necessary to develop the high oil inducers with the rapid development of automatic haploid identification. So the objective of this study was to fine-map qhirl locus and to study the method of marker-assisted selection for inducers, finally to improve the efficiency of DH technology.This paper is mainly on (1) fine-map qhirl locus,(2) develop haploid inducer lines using MAS of the qhirl locus,(3) analysis on the methods of haploid identification of OC based on high oil inducers.The major results were as follows:1) We screened a mapping population of14,375F2plants produced from a cross between haploid inducer UH400and non-inducer line1680to identify14recombinants. And we were able to narrow down the qhirl locus to a243kb region flanked by markers X291and X263based on B73sequence. We found that the qhirl locus also increase the embyro abortion rate, decrease the number of diploid crossing kernels, and a strong selective disadvantage as indicated by significant segregation distortion against inducer genotype.2)The two population of cross GY923×CAU5and cross B73×CAU2were constructed to analysis the effect of marker assisted selection for haploid induction rate. We constructed an F2population, two backcross populations that were backcrossed to the inducer CAU5and the high oil inbred line GY923respectively, and subjected continuous selfing. In each cycle, three different parameters including kernel OC, marker genotype at qhirl and HIR were used for pedigree selection; A marker-assisted selection of qhirl locus method was adopted during the breeding process that backcross to the B73two generations and selfed three generations were included. Finally three high oil inducer lines were developed, with an OC of approximately8.86%, an HIR of approximately8.54%, superior agronomic performance, and CAUB73was developed with an HIR of approximately15.38%, and the range was4.68%-30.55%based on12testers. Our results confirm the notion that HIR selection combined with MAS for qhirl is an effective approach for haploid inducer breeding3) Seven inbred lines and ten hybrids were induced by two high oil inducers CHOI1and CHOI3. The results showed that the xenia effect of CHOI1was0.43, the xenia effect of inbred line was from0.30-0.56, and the xenia effect of hybrids was from0.31-0.52; and the xenia effect of CHOI1was0.40, the xenia effect of inbred line was from0.27-0.57and the xenia effect of hybrids was from0.32-0.54. The difference in the mean OC of haploid and diploid for CHOI3was2.16%on average, the range was1.51%-2.66%, and the difference in the mean OC of haploid and diploid for CHOI3was1.96%on average, the range was1.38%-2.46%. It suggested the CHOI3has a better haploid identify efficiency than CHO3. When source was induced by CHOI1, and μ+1.645σ OC of haploid from the source induced as crucial points, the results showed that the haploid missing rate was below10%and the haploid accuracy rate was beyond90%.