| Core of maize crossbreeding is seed selection of elite inbred lines. Applying regular breeding method to generate homozygous and stable selfing lines needs bagging selfing of 5-8 generations after hybridization, while applying inducer line haploid induction technology can breed pure lines with two generations, which technology largely increases breeding efficiency. Haploid-based technology has been widely used in breeding of selfing line and becomes one of the effective technologies for commercialized breeding of maize though, there are a lot of problems existing in haploid breeding technology, such as trait of haploid inducer line, insufficient pollen quantity, low doubling rate and harmful effects of inducer line gene segments on DH line, etc. Research indicates that DNA segments of male parent inducing line infiltrating into haploid leads to pollutions of deleterious genes, which has significant influences on breeding and utilization of fine DH line. In this article, research on pollutions on DNA segments of male parent inducing line in haploid breeding is carried out in order to provide references for maize haploid breeding. The research results are as follows:(1) 82 maize inducer material groups bred in our laboratory were assorted using 40 pairs of core markers to carry out research on genetic diversity of inducer line groups. Among 40 core primers, 35 primers can augment clear strips with polymorphism in the inducer lines. Totally 152 alleles are augmented with 4.34 alleles per marker, range of variation of each allele is 2-7, mean value of PIC is 0.442 and range of variation of PIC mean value is 0.113-0.677. 82 inducer lines for test were classified into 4 groups based on cluster analysis to inducer lines for test with UPGMA method. In combination with inductivity analysis, average induction rate of the JS6-2-based first group is 11.8%; average induction rate of the JS3-11-based second group is 8.7%; JAAS3 inducer is the third group; and Stock6 is the forth group.(2) Research on infiltration of inducer line fragment into haploid was carried out using SRR marker with polymorphism between inducer and crossing parents. Among 227 maize haploid, 13 inducer line strips were detected in 11 haploids and 4.9% of the haploids carried inducer fragments. Among the 11 haploids, inducer line strips were detected in only 1 locus of 10 haploids, accounting for 2.38% of the detected loci, and inducer line strips were detected in 3 loci of No.35 haploid, accounting for 7.14% of the detected loci. Among 9534 detected loci, detection rate of inducer line strips was 0.136%, wherein 5 loci showed heterozygosis strips, 8 loci showed homozygous inducer line strips and markers of inducer line strips of 9 loci were found in 7 chromosomes. Further study discovered that 5 markers of No.35 haploid in chromosome bin105 showed heterozygosis strips. This result indicated that inducer line fragments(probably large fragments) could infiltrate into haploid with low frequency, which provided a new proof for the theory of haploid forming chromosome elimination.(3) Research on segregation of molecular marker of maize haploid group and DH group derived from B12×M5972 was carried out using SSR molecular marker. The results showed that regarding haploid group, no segregation distortion marks were detected in the observed SSR markers, and no segregation distortions to male parent or female parent were detected after testing observed values of all markers as a whole. As for DH group, among 60 detected markers, segregation distortions were detected in 4 markers, wherein 3 markers deviated to hybrid female parent B12 and 1 marker deviated to hybrid male parent M5972. When testing observed values of all markers as a whole, no segregation distortions of DH group to male parent or female parent were detected. The above results indicated that segregation distortions might appear during the doubling process of haploid which should be given full consideration when making genetic maps using DH group in the future.(4)Heterotic grouping of 76 DH lines taking B12×M5972 as materials is carried out using SSR molecular marker. Tested material B12 belongs to Non-Reid group and M5972 belongs to DOM group. 76 DH lines are classified using core primer into: DH line of partial male parent M5972, DH line of partial female parent B12 and the in-between DH line. Heterotic grouping of 76 DH lines and their parents and 8 inbred lines lines are carried out as well using core primer, and the results show that B12 and M5972 are not classified into Non-Reid group or DOM group. But when classifying 76 DH lines by adding labeling primer with polymorphism between parents B12 and M5972 based on 40 pairs of core primers, 76 DH lines are classified into partial male parent group and partial female parent group; when classifying 76 DH lines and their parents plus with 8 inbred lines at the same time, parents B12 and M5972 of DH lines are classified into Non-Reid group and DOM group. The results show that the method of combining 40 pairs of core primers with labeling primers with parent polymorphism to group DH lines is superior to the method of only using 40 pairs of core primers. |
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