Submitted to: Studies in Mycology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/30/2010
Publication Date: 3/22/2011
Citation: Hirooka, Y., Rossman, A.Y., Chaverri, P. 2011. Morphological and phylogenetic analyses of the Nectria cinnabarina species complex. Studies in Mycology. 68:35-56. Interpretive Summary: Fungi are a group of organisms that cause billions of dollars damage each year to agricultural and forest resources in the United States. One fungus causes a serious disease known as coral spot of apples and other hardwood trees. This fungus occurs throughout the world on a broad range of plants. For years scientists have suspected that this fungus was actually more than one species. In this research many isolates of this fungus were studied from different plants and regions. The microscopic structures of these fungi were observed and the isolates analyzed genetically. It was discovered that what was considered one species is actually four different species. This research provides descriptions and illustrations of the four species along with a key for identification. This paper will be used by forest and plant pathologists to identify the fungi that occur on fruit and other woody tree crops.
Technical Abstract: The genus Nectria is typified by Nectria cinnabarina, a wood-inhabiting fungus common in temperate regions of the northern hemisphere. To determine the diversity of N. cinnabarina, specimens and cultures from Asia, Europe and North America were obtained and examined. Their phylogeny was determined using sequences of multiple loci, specifically act, ITS, LSU, rpb1, tef1 and tub. Based on these observations four species are recognized within the N. cinnabarina species complex. Each species is described and illustrated based on molecular sequence analyses, specimen morphology, and cultural characteristics. An epitype specimen is designated for Nectria cinnabarina sensu stricto and this species is recircumscribed as having 2-septate ascospores and long stipitate sporodochia. Nectria dematiosa, previously considered a synonym of N. cinnabarina, has up to 2-septate ascospores and astipitate sporodochia or no anamorph on natural substrate. A third species, Nectria nigrescens, has up to 3-septate ascospores and short to long, stipitate sporodochia. One newly described species, Nectria asiatica with its distribution restricted to Asia, has up to 1-septate ascospores and short, stipitate sporodochia. Young conidia and mature conidia developing on SNA were observed for each species. Mature conidia of N. asiatica, N. cinnabarina, and N. nigrescens but not N. dematiosa bud when the mature conidia are crowded. On PDA the optimal temperature for growth for N. dematiosa is 20 °C, while for the other three species it is 25 °C. Based on our phylogenetic analyses, three subclades are evident within N. dematiosa. Although subtle cultural and geographical differences exist, these subclades are not recognized as distinct species because the number of samples is small and the few specimens are insufficient to determine if morphological differences exist in nature.