Triploid Hybrids of 2x Lingonberry (Vaccinium vitis-idaea) by 2x Black Highbush Blueberry (V. fuscatum) and 2x Elliott's Blueberry (V. elliottii) as Evidence of a Genome Balance Requirement for Hybridization Success

Hybridizations were made between a 2x V. vitis-idaea (sect. Vitis-idaea, lingonberry) and 2x V. fuscatum (sect. Cyanococcus, Black Highbush Blueberry) as part of a project aimed at understanding the crossability and compatibility of these but specifically aimed at assessing the possibilities for improvement and utilization of lingonberry. The crosses succeeded at a low level, and six hybrids were produced and genetically verified. When tested for ploidy level, five of the six hybrids were found to be triploids and one was found to be a tetraploid. Hybrids were intermediate in morphology and only fertile at very low levels, largely due to their triploid nature. Several of these hybrids produced progeny when used as females and pollinated with 6x V. virgatum-derived males, indicating viable unreduced 2n ovules. Similar crosses were made between lingonberry and 2x V. elliottii (sect. Cyanococcus, Elliott's Blueberry). These crosses produced two genetically verified hybrids, which were also determined to be triploids. These hybrids were effectively sterile. The production of triploids from 2x x 2x crosses indicates that there is a natural selection for a reproductive genome balance of two V. vitis-idaea:one Cyanococcus. The success of secondary hybridizations with hexaploid materials suggests that the triploid hybrids may be used to advance the utilization and recombination of lingonberry germplasm.