Botanica Pacifca. A journal of plant science and conservaton. 2018. 7(2): 47–51 DOI: 10.17581/bp.2018.07207 47 ©Botanical Garden-Insttute FEB RAS. 2018 ABSTRACT A new species, Diderma velutinum, is described and illustrated by LM and SEM mic- rographs. Two specimens of this species were found in moist chamber cultures on the pieces of the bark of living tree of Phellodendron amurense, which was collected in July 2016 and July 2017 in the Kedrovaya Pad State Nature Biosphere Reserve (the Russian Far East). The main distinguishing features of this species are triple peridium, large spherical columella and ochraceous colour of sporangia clustered in dense groups. The partial 18S rRNA gene sequences of D. velutinum differ con- siderably from all sequences of Diderma species available to the moment. Keywords: Amoebozoa, COI, DNA barcoding, EF1A, morphology, Physarales, SEM, taxonomy, 18S rRNA РЕЗЮМЕ Бортников Ф.М., Щепин О.Н., Гмоинский В.И., Приодко И.С., Новожилов Ю.К. Diderma velutinum, новй вид рода Diderma (Myxo mycetes) с болой колонкой и треслойнм перидием из России. Новй вид Diderma velutinum описан и проиллстрирован микроотогра- ими, поленнми с помо светового и сканирего лектронно- го микроскопов. Два образа того вида бли полен методом влажн камер на рагмента кор живого дерева барата амрского (Phellodendron amurense), собранн в иле 2016 и иле 2017 года в госдарственном при- родном биосерном заповеднике «Кедрова Пад» (Приморский Край). Основнми отлиителнми особенностми того вида влтс тре- слойнй перидий, бола сериеска колонка и ориста окраска спо- рангиев, собранн в плотне грпп. Нклеотидне последователности рагмента гена 18S рРНК нового вида показват знаителне отлии от имеис последователностей дрги видов рода Diderma. Клеве слова: Amoebozoa, COI, EF1A, Physarales, ДНК-баркодинг, морологи, СЭМ, таксономи, 18S рРНК Fedor M. Bortnikov 1 * e-mail: f.m.bortnikov@gmail.com Oleg N. Shchepin 2 e-mail: ledum_laconicum@mail.ru Vladimir I. Gmoshinskiy 1 e-mail: rubisco@list.ru Ilya S. Prikhodko 2 e-mail: hypnothotep@gmail.com Yuri K. Novozhilov 2 e-mail: yurinovozhilov@gmail.com 1 Lomonosov Moscow State University, Faculty of Biology, Mycology and Algology Dept., Moscow 119234 Russia 2 V.L. Komarov Botanical Institute RAS, Saint-Petersburg, Russia * corresponding author Manuscript received: 07.09.2018 Review completed: 25.10.2018 Accepted for publication: 30.10.2018 Published online: 31.10.2018 Fedor M. Bortnikov 1 *, Oleg N. Shchepin 2 , Vladimir I. Gmoshinskiy 1 , Ilya S. Prikhodko 2 & Yuri K. Novozhilov 2 Diderma velutinum, a new species of Diderma (Myxomycetes) with large columella and triple peridium from Russia Diderma is one of the three largest genera of myxomyce- tes and currently includes 82 species (Lado 2005–2018) of which 27 are recorded in Russia (unpublished data). During the study of biodiversity of myxomycetes in the Kedrovaya Pad State Nature Biosphere Reserve in 2016, in a moist chamber culture a collection of Diderma was found, which differed from all the described species of this genus. The second collection of this species was obtained in a moist chamber culture after additional sampling of substrates for moist chambers in July 2017 in the same locality. In this paper we describe this new species of Diderma, including the morphological analysis of sporocarps and spores using the light (LM) and the scanning electron microscopy (SEM), and provide partial sequences of 18S rRNA, COI and EF1A genes. MATERIAL AND METHODS Isolates and morphology The moist chamber cultures were used to obtain a new species. This new species was described and illustrated by the frst author at the Department of Mycology and Algo- logy of the Biological Faculty of the Lomonosov Moscow State University. The sampling of the substrates for moist chamber cul- tures was carried out in July 2016 and 2017 in the same loca- lity of the Kedrovaya Pad State Nature Biosphere Reserve. Small fragments of the bark of a living tree were cut out at about 1.5 m height, placed in paper bags and air-dried. In the laboratory, samples were evenly distributed over the bottom of Petri dishes above the flter paper and poured with distilled water. After a day, pH was measured with the pH-meter “Aquilon pH-420” and excess water was drained off. The cultures were incubated at room temperature (18– 22°C) under diffused light for three months and checked for the presence of sporocarps of myxomycetes every 7–14 days, more often in the frst 45 days. Sporocarps of the new species appeared within 50–70 days after the be- ginning of the moist chamber cultures. Plasmodium was seen only in the second setting of moist chamber cultures and after formation it quickly passed to sporangiogenesis. The macroscopic characteristics of air-dried sporocarps were studied with a Leica M80 stereomicroscope (with a