The ethylene 2 receptor gene as a robust molecular marker for intergeneric somatic hybrids between Petunia and Calibrachoa

A 600 bp fragment of the ethylene-receptor gene 2 (ETR2) was sequenced in Petunia and Calibrachoa genotypes and in putative intergeneric somatic hybrids. In total, 16 genus-specific single base pair polymorphisms (SNPs) were detected. These were used to construct, genus specific restriction maps and a Cleaved Amplified Polymorphic Sequence marker with specific 400 bp fragments for Petunia and 550 bp for Calibrachoa. This diagnostic and robust marker is suitable to distinguish Petunia and Calibrachoa and is a valuable tool for the identification of intergeneric somatic hybrids which are currently developed in model breeding programmes. Based on sequence data for the ETR2 fragment, phylogenetic analyses were conducted. Neighbour-Joining trees reveal distinct subgroups of ETR2 of each genus, therefore supporting recent results of molecular phylogenetic studies on Petunia and Calibrachoa. Sequences of putative hybrids are represented in both subgroups, confirming their hybrid status.