Microsporogenesis and crossing behavior of a tetraploid, interspecific inter-EBN hybrid potato

The commercial potato Solanum tuberosum L. autotetraploid, has many wild relatives with the ploidy range of 2–6×, which are suitable sources of traits interesting in potato breeding. However, not all of these species can be readily crossed with cultivated potato due to pre- and post-zygotic barriers. Post-zygotic barrier on Solanum spp. is attributed to their difference in endosperm balance number (EBN). According to the EBN successful crosses need to have a 2:1 ratio of maternal to paternal EBN in hybrid endosperm. Thus, only parents with the same EBN can be crossed. The cultivated potato is 4EBN, while wild allotetraploid relatives such as S. stoloniferum are 2EBN. In this study, meiosis and crossability of an exceptional tetraploid 3EBN hybrid obtained from our previous research by crossing S. stoloniferum × S. tuberosum with 2 and 4EBN testers were studied. Although the exact chromosome pairing analysis was not possible, the formation of several polyvalents in each meiocyte suggests that recombination could occur between different genomes. Meiosis had many irregularities such as unequal segregation as well as having laggard chromosome and micronuclei. Crosses involving the interspecific hybrid, as the male parent with 2 and 4EBN testers were not successful, some of which were apparently due to the pollen–pistil incompatibility. Interestingly controlled self-pollination resulted in viable seeds. Crosses of the interspecific hybrid as pistillate parent in the absence of pre-zygotic barrier in most case were successful. Results of the study confirmed the segregation of EBN value in the gametes of hybrid. It was expected that backcross progeny of this hybrid would be a good source for selecting aneutetraploids.