ORIGINAL ARTICLE Diaporthe from walnut tree (Juglans regia) in China, with insight of the Diaporthe eres complex XinLei Fan 1 & Qin Yang 1 & Jadson D. P. Bezerra 2 & Lourdes V. Alvarez 3 & ChengMing Tian 1 Received: 27 June 2017 /Revised: 10 March 2018 /Accepted: 14 March 2018 # German Mycological Society and Springer-Verlag GmbH Germany, part of Springer Nature 2018 Abstract Species of Diaporthe are important plant pathogenic fungi that commonly occur on a wide range of hosts. They are relatively difficult to identify due to their extreme similarity in morphology and confusing multigene phylogeny, especially in the Diaporthe eres complex. In the present study, isolates were collected from diseased branches of Juglans regia in China. Most strains were clustered into the D. eres species complex based on the combined internal transcribed spacer (ITS) region, partial calmodulin (CAL), histone H3 (HIS), translation elongation factor 1-alpha (TEF1-α) and beta-tubulin (TUB) genes. To focus on this complex, CAL, TEF1-α and TUB were selected in further phylogenetic analyses that showed a better topology compared with combined five-gene phylogeny. Results revealed that all strains which clustered in the Diaporthe eres complex from Juglans regia in China were Diaporthe eres. Results suggested a revised species criterion in the Diaporthe eres complex. The current study uncovered a new species here described as Diaporthe. tibetensis. Keywords Diaporthales . Molecular phylogeny . New species . Species complex . Taxonomy Introduction Members of Diaporthe Nitschke (syn. Phomopsis (Sacc.) Bubák) are plant pathogens, endophytes or saprobes on a wide range of hosts and are responsible for diseases, some of these causing damage in plants of economic importance (Gomes et al. 2013; Chepkirui and Stadler 2017; Guarnaccia et al. 2018). The sexual morph of Diaporthe is characterised by ascomata immersed in the substrate, often erumpent through a stroma with more or less elongated perithecial necks; asci are unitunicate, clavate to cylindrical, eight-spored; ascospores are hyaline, biseriate to uniseriate in the ascus, fusoid, ellipsoid to cylindrical, straight, inequilateral or curved, septate and sometimes with appendages (Wehmeyer 1933; Udayanga et al. 2011; Gomes et al. 2013). The asexual morph is characterised by ostiolate conidiomata pycnidial, with cylindrical phialides producing up to two types of co- nidia; alpha conidia are hyaline, aseptate, fusiform and usually biguttulate, but sometimes aguttulate or having more than two guttules; beta conidia are hyaline, aseptate, filiform, straight or more frequently curved (Wehmeyer 1933; Udayanga et al. 2011; Gomes et al. 2013). More than 1033 epithets for Diaporthe and 976 for Phomopsis were listed in Index Fungorum (January 2018) (http://www.indexfungorum.org/). However, a majority of them may be synonyms due to the unclear linkage of sexual and asexual morphs and the historical species recognition criteria based on morphology, culture characteristics and host affiliation (Wehmeyer 1933; Uecker 1988; Rehner and Uecker 1994; Santos and Phillips 2009). It is widely known that a single Diaporthe species often occurs on taxonomically unrelated hosts, and more than one species can co-occur on the same host plant (Santos and Phillips 2009; Gomes et al. 2013 ). Taylor et al. ( 2000 ) proposed Genealogical Concordance Phylogenetic Species Recognition (GCPSR), Section Editor: Roland Kirschner * ChengMing Tian chengmt@bjfu.edu.cn 1 The Key Laboratory for Silviculture and Conservation of Ministry of Education, Beijing Forestry University, Beijing 100083, China 2 Departamento de Micologia Prof. Chaves Batista, Universidade Federal de Pernambuco, Av. Prof. Moraes Rego, s/n, Centro de Biociências, Cidade Universitária, CEP, Recife, PE 50670-901, Brazil 3 Department of Biology, College of Science, Polytechnic University of the Philippines, Sta. Mesa, Manila, Philippines Mycological Progress https://doi.org/10.1007/s11557-018-1395-4