Novel inter-series hybrids in Solanum, section Petota

Area of Science:

• Plant genetics
• Reproductive biology
• Crop science

Background:

• Sexual hybrids between distantly related Solanum species often fail due to endosperm failure, a post-zygotic reproductive barrier.
• The endosperm balance number (EBN) hypothesis explains this by requiring compatible EBNs between parents for viable seed formation.

Purpose of the Study:

• To investigate inter-crossability and endosperm development in hybrids of distantly related Solanum species.
• To explore strategies for overcoming post-zygotic reproductive barriers in Solanum section Petota.

Main Methods:

• Conducted inter-specific crosses involving Solanum pinnatisectum (1EBN) and various Solanum species with 2EBN and 4EBN.
• Utilized confocal microscopy to analyze hybrid endosperm development, cell-division timing, and tissue collapse.
• Employed post-pollination auxin application and in vitro embryo rescue to generate and verify novel hybrids using microsatellite markers and chromosome counting.

Main Results:

• Successfully generated novel sexual diploid (AAApi) and triploid (AAApiApi) inter-series hybrids between S. verrucosum and S. pinnatisectum using auxin treatment and embryo rescue.
• Auxin application did not prevent endosperm collapse in inter-ploidy crosses between S. pinnatisectum and S. tuberosum, resulting in no embryo formation.
• Confirmed endosperm failure as a significant post-zygotic barrier in various inter-specific Solanum crosses.

Conclusions:

• Strategies involving phytohormone application and embryo rescue can facilitate the generation of inter-series Solanum hybrids.
• Endosperm balance number (EBN) compatibility remains a critical factor in successful Solanum hybridization.
• Further research into overcoming reproductive barriers is essential for advancing Solanum breeding programs.