Abstract
Most chrysanthemum cultivars are self-incompatible, so it is very difficult to create pure lines that are important in chrysanthemum breeding and theoretical studies. In our previous study, we obtained a self-compatible chrysanthemum cultivar and its self-pollinated seed set was 56.50%. It was interesting that the seed set of its ten progenies ranged from 0% to 37.23%. Examination of the factors causing the differences in the seed set will lead to an improved understanding of chrysanthemum self-incompatibility, and provide valuable information for creating pure lines. Pollen morphology, pollen germination percentage, pistil receptivity and embryo development were investigated using the in vitro culture method, the paraffin section technique, scanning electron microscopy and transmission electron microscopy. Moreover, RNA sequencing and bioinformatics were applied to analyzing the transcriptomic profiles of mature stigmas and anthers. It was found that the self-pollinated seed set of “Q10-33-1①”,”Q10-33-1③”,”Q10-33-1④” and “Q10-33-1⑩” were 37.23%, 26.77%, 7.97% and 0%, respectively. The differences in fertility among four progenies were mainly attributable to differences in pollen germination percentage and pistil receptivity. Failure of the seed set in “Q10-33-1⑩” was possibly due to self-incompatibility. In the transcriptomic files, 22 potential stigma S genes and 8 potential pollen S genes were found out.
Highlights
The cultivated chrysanthemum is generally allohexaploid and aneuploidy [1,2] with a highly heterozygous genotype, and its trait inheritance and genetic background are extremely complex [3,4] so it is very hard to create chrysanthemum pure lines
The results indicated that they were really “Q10-33-1”’s progenies, and that it would be beneficial to analyze differences in self-fertility because of similar genetic background
This study shows that the self-pollinated seed set of chrysanthemum is mainly affected by pollen germination percentage, the germination behavior of pollen grains on stigmas, pollen tube growth and embryo development
Summary
The cultivated chrysanthemum is generally allohexaploid and aneuploidy [1,2] with a highly heterozygous genotype, and its trait inheritance and genetic background are extremely complex [3,4] so it is very hard to create chrysanthemum pure lines. Chrysanthemum pure lines are very important for the utilization of heterosis and genome research. Self-fertilization is an important means to develop chrysanthemum pure lines. Pure lines can be created by the multigenerational selfing of self-compatible chrysanthemum cultivars. Most cultivated chrysanthemum is self-incompatible [1,5]. Understanding the mechanism of self-incompatibility (SI) is crucial for the development of chrysanthemum pure lines
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