Natural hybridization of Y ezo and S akhalin spruce in central H okkaido, revealed by DNA markers with contrasting modes of inheritance

Yezo spruce ( P icea jezoensis var. jezoensis ) and Sakhalin spruce ( P icea glehnii ) occur across H okkaido and co‐occur in some forest habitats. This leads to the potential for natural hybridization between these two species, which has been shown to occur at low frequencies. The purpose of this study was to identify these hybrids and their possible mating patterns, using various P inaceae DNA markers with different modes of inheritance. The markers used were maternally inherited mitochondrial DNA (mt DNA ), paternally inherited chloroplast DNA (cp DNA ) and biparentally inherited nuclear microsatellites (n SSRs ). Seven putative natural hybrids, four artificially‐crossed F 1 hybrids, four parent plants from each species, and two artificially‐backcrossed hybrids of putative natural hybrids and their parents were analyzed using the diagnostic DNA markers developed in this study. We found Y ezo spruce and S akhalin spruce to be distinct ( J and G types, respectively), and the modes of inheritance held true for the two species, as was previously reported to be the case in P inaceae. Four of the seven putative natural hybrids harbored J ‐type cp DNA , G ‐type mt DNA and J / G ‐type n SSRs , indicating that natural F 1 hybrids are likely to arise from a G (female) × J (male) crossing. One natural hybrid harbored G ‐type cp DNA , J ‐type mt DNA and J / G ‐type n SSRs , which implies that hybrids produced by J (female) × G (male) crossings occur at low frequencies. The two remaining hybrids harbored J ‐type cp DNA and mt DNA with either J / G or J / J ‐type n SSRs , suggesting that they may be F 2 hybrids resulting from backcrossing between an F 1 hybrid and a Y ezo spruce.