Cross-incompatibility between two sympatric polyploid Solanum species

Area of Science:

• Plant reproductive biology
• Genetics
• Evolutionary biology

Background:

• Closely related sympatric species S. gourlayi (4x) and S. oplocense (6x) exhibit potential for interspecific interactions.
• Understanding reproductive isolation mechanisms is crucial for plant speciation and gene flow studies.

Purpose of the Study:

• To investigate the cross-compatibility and identify barriers to hybridization between S. gourlayi and S. oplocense.
• To elucidate the genetic basis of observed cross-incompatibility (CI) and self-incompatibility.

Main Methods:

• Reciprocal crosses were performed between S. gourlayi (4x) and S. oplocense (6x).
• Pollen-pistil interactions were analyzed using fluorescent microscopy to detect incompatibility sites.
• Self-compatibility of parental species and F1 hybrids was assessed.

Main Results:

• Hybridization between S. gourlayi and S. oplocense proved difficult due to pollen-pistil incompatibility.
• Incompatibility reactions occurred at distinct sites (stigma, style, ovary) depending on the direction of the cross.
• F1 hybrids were self-incompatible, while parental species were self-compatible.

Conclusions:

• A dominant gene-based cross-incompatibility (CI) system, involving pistil and pollen genes, likely explains the observed reproductive barriers.
• This CI system facilitates gene exchange between sympatric populations while maintaining species integrity.
• The findings provide insights into mechanisms of reproductive isolation in polyploid plant species.