Identification of symbiotic arbuscular mycorrhizal fungi in Korean Ginseng roots by 18S rDNA sequence

Abstract

This study was carried out to perform the identification of arbuscular mycorrhizal fungi colonized in Korean Ginseng roots. Samples were soils and roots from various Ginseng cultivation sites of Chungcheong province in Korea. Those approaches include thorough investigation of morphological characteristics of spores harvested from Ginseng root associated soil and molecular biological identification of AM fungi in Ginseng roots. Based on the morphology of spores isolated from the soils, five distinguishable spore morpho-types AM fungi were found; Glomus mosseae, Glomus intraradices, Gigaspora margarita, Acaulospora longular and Gigaspora gigantea. Among these, Glomus mosseae, Glomus intraradices and Acaulospora longular were the most commonly encountered species. Glomus and Acaulospora were dominant with frequencies of 55% and 25%, respectively. AM fungi colonization rates were progressed with the increase of cultivation period, relatively low infection rate in two year-old root, heavily infected in three year-old root, cube shape of intensive hyphal coil and distributed toward longitudinally in four year-old root, and eventually clear internal arbuscular hypae and vescicle were observed in the five year-old roots. By sequence analysis of the small subunit of the nuclear ribosomal DNA (18S rDNA), it was disclosed that Ginseng roots were associated with AM fungi as follows; 4 Glomus and 1 Acaulospora genera, Glomus sinuosum (AJ133706), Glomus fasciculatum (Y17640), Glomus intraradices (AY635831), Glomus mossae (AJ699064) and Acaulospora spp. (AY394664). There were observed only one AM fungus, Glomus sinuosum, in one year-old Ginseng root, but three AM fungi, Glomus fasciculatum, Glomus intraradices and Glomus sinuosum in two year-old root. Three year-old root was associated with two AM fungi, Glomus sinuosum and one new AM fungus, Acaulospora spp. (AY394664). There were found three AM fungi, Glomus sinuosum, Glomus fasciculatum and Glomus intraradices, in five year-old root.