Reinforced evidence on partial compatibility between Pinus sylvestris and Pinus mugo and on maternal inheritance of chloroplast DNA in the Pinus mugo × Pinus sylvestris cross

Abstract The crossability relationship between Scots pine (Pinus sylvestris L.) and mountain dwarf pine (Pinus mugo Turra) was tested under field conditions using an artificial pollination approach. There was partial compatibility between the parental species, as evidenced by the amount of filled seeds in their reciprocal crossings and in control variants from self-pollination, controlled intraspecific outcrossing and open pollination of mother trees. The crossability degree in P. sylvestris × P. mugo was characterised by the index 0.15, and the reciprocal crossing by the index 0.18. Crossability of P. sylvestris and P. mugo with their putative hybrid individuals was much higher; the number of filled seeds was comparable with that of the control variants. The reciprocal crossings of P. sylvestris and P. mugo species were highlighted by the opposite inheritance of their chloroplast DNA (cpDNA). The paternal cpDNA inheritance in P. sylvestris × P. mugo and maternal cpDNA inheritance in P. mugo × P. sylvestris was repeatedly confirmed using the cpDNA trnV-trnH/HinfI marker as well as the newly developed partial cpDNA trnV-trnH/AseI marker. The nature of the latter is described in terms of the nucleotide sequence.