Genetic characteristics and ploidy trigger the high inducibility of double haploid (DH) inducer in Brassica napus

Abstract

Background: Our recently reported doubled haploid (DH) induction lines e.g., Y3380 and Y3560 are allo-octoploid (AAAACCCC, 2n = 8× ≈ 76), which can induce the maternal parent to produce DH individuals. Whether this induction process is related to the production of aneuploid gametes form male parent and genetic characteristics of the male parent has not been reported yet.

Results: Somatic chromosome counts of DH inducer parents, female wax-less parent (W1A) and their F₁ hybrid individuals revealed the reliability of flow cytometry analysis. Y3560 has normal chromosome behavior in metaphase I and anaphase I, but chromosome division was not synchronized in the tetrad period. Individual phenotypic identification and flow cytometric fluorescence measurement of F₁ individual and parents revealed that DH individuals can be distinguished on the basis of waxiness trait. The results of phenotypic identification and flow cytometry can identify the homozygotes or heterozygotes of F₁ generation individuals. The data of SNP genotyping coupled with phenotypic waxiness trait revealed that the genetic distance between W1A and F₁ homozygotes were smaller as compared to their heterozygotes. It was found that compared with allo-octoploids, aneuploidy from allo-octoploid segregation did not significantly increase the DH induction rate, but reduced male infiltration rate and heterozygous site rate of induced F₁ generation. The ploidy, SNP genotyping and flow cytometry results cumulatively shows that DH induction is attributed to the key genes regulation from the parents of Y3560 and Y3380, which significantly increase the induction efficiency as compared to ploidy.

Conclusion: Based on our findings, we hypothesize that genetic characteristics and aneuploidy play an important role in the induction of DH individuals in Brassca napus, and the induction process has been explored. It provides an important insight for us to locate and clone the genes that regulate the inducibility in the later stage.

Keywords: Aneuploidy; Bassica napus L; Doubled haploid inducer; Flow cytometry; Homozygous sites rate; Phenotypic identification; Ploidy; SNP genotyping.