Hybrid variegation in the genus Pelargonium

Area of Science:

• Plant genetics
• Cell biology
• Molecular genetics

Background:

• Pelargonium zonale exhibits hybrid variegation.
• Variegation involves the sorting of plastids within plant tissues.
• Periclinal chimeras are common in Pelargonium.

Purpose of the Study:

• To analyze the genetic and cytological basis of hybrid variegation in Pelargonium zonale.
• To investigate the sorting mechanism of plastids in variegated Pelargonium hybrids.
• To determine the role of nuclear-plastome interactions in variegation.

Main Methods:

• Genetical and cytological analysis of Pelargonium zonale crosses.
• Observation of plastid sorting in green-white variegated plants.
• Restriction endonuclease analysis of plastid DNA (cpDNA) using EcoRI and BamHI.
• Comparison of cpDNA cleavage patterns in green and white tissues.

Main Results:

• Six types of periclinal chimeras were identified in variegated Pelargonium.
• Distinct cpDNA cleavage patterns were observed for the parental plastomes.
• 'Roseum' cpDNA was found in green tissues, and 'Stadt Bern' cpDNA in white tissues.
• The sorting of parental plastids was detailed at the cpDNA level.

Conclusions:

• A disharmony exists between the F1-hybrid nucleus and the 'Stadt Bern' plastome.
• This nuclear-plastome incompatibility blocks normal differentiation of 'Stadt Bern' plastids.
• The study elucidates the genetic and molecular mechanisms underlying variegation in Pelargonium.