Development of SCAR markers distinguishing pure seedlings of the endangered species Morus boninensis from M. boninensis × M. acidosa hybrids for conservation in Bonin (Ogasawara) Islands

Abstract

To support the recovery of Morusboninensis Koidz. (Moraceae), a criticallyendangered species distributed in the BoninIslands of Japan, we need to distinguishbetween pure M. boninensis and hybrid(M. boninensis × M. acidosa Griff.)seedlings within populations derived from M. boninensis mother trees. Therefore, wedeveloped three co-dominant SCAR (SequenceCharacterized Amplified Region) markers todistinguish between M. boninensis, M. acidosa and their hybrids. All threemarkers could clearly identify the species andthe hybrids, although we observed one case of aputative null allele or a backcross at onelocus (Mos0251-1). Hence, we suggest that pureand hybrid seedlings could be unambiguouslyidentified by the simultaneous use of the threemarkers. When we investigated a seedlingpopulation produced by a single mother treegrowing in the Iguma-bay population ofHaha-jima Island, the proportion of embryosformed by pollination from M. acidosapollen was about 13%. All hybrid seedlingsidentified according to the molecular markersshowed incisions in their leaves, amorphological character that has never beenobserved in pure M. boninensisindividuals. Our results suggest that M.boninensis can potentially be multiply byexcluding hybrids from the seedling pools,using incisions on the leaves as morphologicalmarkers to identify them.