Abstract
ABSTRACTDogroses, Rosa sect. Caninae (x=7, 2n=28, 35 or 42) grow wild in the Scandinavian countries. Hips from this section have a particular aroma and are used in Sweden for making a traditional dessert dish, rose hip soup. Commercial production has recently been initiated with field-grown selections from the Balsgård rose hip breeding program. The species are often used as rootstocks for ornamental roses and some of them could also be a potential source of resistance for e.g. blackspot. All species within the section have a unique meiosis with 7 bivalents regardless of ploidy level. Viable pollen cells contain 7 chromosomes and egg cells 21, 28 or 35 chromosomes. In a study of a pair of reciprocal crosses between R. dumalis X R. rubiginosa (both 2n=35), molecular RAPD markers showed that all 78 progeny plants inherited almost all of the seed-parent specific marker. In contrast, only half of the pollen-specific markers were transmitted to any of the progenies. Most of the pollen-specific markers were found in 75–90% of the progenies, but there was also one marker that was only found in 50% of the progenies and three markers that only appeared in 2–4 plants. The study also showed that the species were genetically very similar. Nine progeny plants have never received any of the pollen-specific markers and these plants were subjected to an extended study with additional molecular markers. Reproductive characters as pollen viability, amount and weight of seeds and fruit weight variables were studied on all the progeny plants. Pollen viability was approx 25% in the parent plants whereas the hybrid progenies had a pollen viablity of 0–10%. Of the nine progeny plants which lacked pollen-specific RAPD markers even in this extended study, seven had a pollen viability close to that found in their seed-parents. This suggests that facultative apomixis occurs in this section, but it is difficult to quantify its contribution to the already low genetic variability.
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