| Summary: | Self-incompatibility (SI) is a widespread genetic mechanism which prevent self-fertilization in angiosperms. The genus Petunia of the Solanaceae serve as a model for SI research due to its short life cycle and accessible floral morphology. In Petunia, SI is mediated by S-RNase dependent degradation of self-pollen RNA within the style, arresting pollen tube growth. Breakdown of SI confers self-compatibility (SC), with implications for breeding and yield optimization.
This study investigates the genetic basis of SI breakdown in hybrids of P. inflata × P. hybrida. For the first time, it provides a concise analysis of the novel PiSd-allele and its association with SC across five generations. Genotypic and phenotypic analyses, including genomic PCR, identification of S-alleles by sequencing, and controlled self-pollinations were performed on lines carrying PhS3 and PiSd alleles.
The novel PiSd allele correlates with SI breakdown, suggesting functional alteration in associated SLF genes, which remain uncharacterized. The segregation ratios confirm the linkage between the PiSd and SI breakdown. Future molecular dissection of PiSd-linked SLF genes will firstly provide an understanding of the mechanism of SI breakdown and ultimately is warranted to inform targeted breeding strategies in Petunia and beyond.
The second stage of this research is focused on SI mechanism in Schlumbergera truncata. S. truncata is among the most widely cultivated cactus species notable for its diverse array of colourful flowers and various flower forms. SI in S. truncata is under GSI control. This study tests whether the GSI mechanism in S. truncata is of the S-RNase system and explores whether it is homologous to that in the rosids and the asterids, as it likely seems by the phylogenetic relationships of angiosperms. This was achieved by analysing the genetic and phenotypic characteristics of different lines, determining the presence and functionality of S-alleles within the study lines.
This study successfully identified three S-alleles in the S. truncata F1 progeny lines. All three are present in the five alleles identified previously. These S alleles identification combined with the data of the classic diallele self and cross-pollination and the formed incompatibility/compatibility groups strongly suggest the likelihood of a S-RNase mechanism under the control of a single locus occurring in the S. truncata population.
These findings in S. truncata combined contribute to a deeper understanding that the S-RNase mechanism is more widely functional and polymorphic among angiosperms, which adds to the insights of their evolutionary relationships. A question for future study is whether this mechanism is functional through self-recognition or non-self-recognition pathways.
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