New karyotypes of an interspecific hybrid of Torenia fournieri and Torenia baillonii and its progenies

Although Torenia fournieri (2n=2x=18) and Torenia baillonii (2n=2x=16) have different chromosome numbers, almost all of the parental chromosomes form bivalents by interspecific pairing during meiosis in interspecific hybrids. Here, we produced another hybrid between the two species and its six BC1F1 progenies (F1 hybrid × T. baillonii). These plants had previously unreported chromosome compositions: the total chromosome number was 34, as expected for allotetraploids, but some T. fournieri chromosomes were gained and some T. baillonii chromosomes were lost. Plants with these new karyotypes grew well and showed different morphologies. This study indicates that two parental genomes in interspecific hybrids share several interchangeable homoeologous chromosomes.