Abstract
Breeding programs in ornamentals can be facilitated by integrating knowledge of phylogenetic relatedness of potential parents along with other genomic information. Using AFLP, genetic distances were determined for 59 Geranium genotypes, comprising 55 commercial cultivars of the three subgenera of a total collection of 61 Geranium genotypes. A subgroup of 45 genotypes, including intragroup and intergroup hybrids, were selected and further characterized for genome sizes and chromosome numbers. The variation in genome size ranged from 1.51 ± 0.01 pg/2C to 12.94 ± 0.07 pg/2C. The chromosome numbers ranged from 26 to 108–110 with some hybrids showing an aberrant number of chromosomes based on their parents’ constitution. All chromosome numbers of Geranium are an even number, which presumes that unreduced gametes occur in some cross combinations. Overall, parental difference in genome size and chromosome number were not limiting for cross compatibility. Good crossing compatibility was correlated to a Jaccard similarity coefficient as parameter for parental relatedness of about 0.5. Additionally, parent combinations with high differences in the DNA/chromosome value could not result in a successful cross. We expect that our results will enable breeding programs to overcome crossing barriers and support further breeding initiatives.
Highlights
The Geraniaceae comprises the genera Geranium (430 species), Pelargonium (280 species), Erodium (80 species) and Monsonia (40 species) resulting in a total number of more than 700 species [1,2,3]
Based on a Principal Coordinate Analysis (PCoA) with two factors explaining 17.6% and 13.8% of the variation, a division in the subgenera of the Geranium genus is given (Figure 1): Geranium and Erodioidea subgenera are more closely related compared to the subgenus Robertium
We can conclude that knowledge about the genetic distance, genome size or chromosome number can support breeding efforts in Geranium
Summary
The Geraniaceae comprises the genera Geranium (430 species), Pelargonium (280 species), Erodium (80 species) and Monsonia (40 species) resulting in a total number of more than 700 species [1,2,3]. Erodium and Geranium are phylogenetically closest related [4]. Geranium or cranesbill is a genus divided into three subgenera: Erodioidea with 22 species in four sections, Robertium with 30 species in eight sections, and Geranium with 380 species in at least ten sections [5]. This division into sections is still in flux [6]. A cosmopolitan genus, is adapted to well-watered soils and cool temperate regions [7]. The majority of the species originate in the temperate northern part of Eurasia
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