Can Knowledge of Genetic Distances, Genome Sizes and Chromosome Numbers Support Breeding Programs in Hardy Geraniums?

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.

Prediction Model for Breeding Hardy Geraniums

“…This is probably due in part to the high number of replicates and good data coverage. Previous research also supports the importance of cJaccard in determining cross compatibility [26], and based on hybrids described in the literature, we hypothesized that good cross compatibility was correlated with a cJaccard of 0.5 and that the maximum value of cJaccard for hybridization is 0.87. According to our logistic regression model utilizing our hybridization data, cJaccard values of 0.5 and 0.87 correspond to a seed development crossing success of 39% or 4.6%, respectively.…”

“…Four different measures were used to characterize the parental difference between two parents (P1 and P2) in each cross: Chrom, DNA, Style, and cJaccard (cJaccard = 1 − Jaccard, which is the complement of Jaccard similarity and represents Jaccard distance) (Tables S2-S4). Chrom expresses the parental difference between the chromosome number in a cross [26]. DNA is the difference in genome size/chromosome number (pg/chromosome) [26].…”

“…Chrom expresses the parental difference between the chromosome number in a cross [26]. DNA is the difference in genome size/chromosome number (pg/chromosome) [26]. Style is the difference in style length (mm), which was measured using a ruler when the style was fully developed.…”

Karyology and Genome Size Analyses of Iranian Endemic Pimpinella (Apiaceae) Species

“…These relative differences could be used for breeding programs by facilitating chromosome identification in hybrid populations and derivatives in Pimpinella . Parent combinations with relative differences in the chromosome numbers/type due to chromosome pairing could result in a successful cross ( Hamidi et al, 2018 ; Akbarzadeh et al, 2021 ). Three species – S3 ( P. tragium ), S13 ( P. anisactis ), and S15 ( P. khorasanica ) – are very similar to each other from the viewpoint of anatomy, and we are not able to separate them with anatomical features.…”

Investigations on Nuclear DNA Content and DNA Synthesis in Plants and Fungi Using Flow Cytometry and Fluorescence Microscopy

“…In such breeding programs, knowledge of the genome sizes of potential parents can be helpful in predicting cross-compatibility. With the aim of supporting breeding programs of Geranium , Akbarzadeh et al [ 7 ] estimated genome size, chromosome number, and genetic relationship between 61 different Geranium species and commercial cultivars. They recommend the pairwise Jaccard similarity coefficient as a preliminary determinator for successful hybrid production in this genus.…”