Species of Diaporthe are considered important plant pathogens, saprobes, and endophytes on a wide range of plant hosts. Several species are well-known on citrus, either as agents of pre- or post-harvest infections, such as dieback, melanose and stem-end rot on fruit. In this study we explored the occurrence, diversity and pathogenicity of Diaporthe species associated with Citrus and allied genera in European orchards, nurseries, and gardens. Surveys were carried out during 2015 and 2016 in Greece, Italy, Malta, Portugal, and Spain. A total of 79 Diaporthe strains were isolated from symptomatic twigs, branches and trunks. A multi-locus phylogeny was established based on five genomic loci (ITS, tef1, cal, his3 and tub2), and the morphological characters of the isolates determined. Preliminary pathogenicity tests were performed on lemon, lime, and orange plants with representative isolates. The most commonly isolated species were D. foeniculina and D. baccae, while only four isolates of D. novem were collected. Two new Diaporthe species, described here as D. limonicola and D. melitensis spp. nov. were found associated with a new devastating dieback disease of lemon plants. Furthermore, one cluster of sterile Diaporthe isolates was renamed as D. infertilis. Pathogenicity tests revealed most of the Citrus species as susceptible to D. baccae, D. foeniculina, and D. novem. Moreover, D. limonicola and D. melitensis caused serious cankers affecting all the Citrus species tested. This study is the first report of D. baccae and D. novem on citrus in Europe, and the first detection of a new Diaporthe canker disease of citrus in Europe. However, no isolates of D. citri were found. The study improves our understanding of the species associated with several disease symptoms on citrus plants, and provides useful information for effective disease management.

中文翻译：

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欧洲的新兴柑橘病是由Diaporthe物种引起的。

Diaporthe的种类被认为是各种植物宿主上的重要植物病原体，腐生菌和内生菌。柑橘上有几种物种是众所周知的，既可以作为收获前或收获后感染的媒介，例如死皮，黑色素和果实上的茎端腐烂。在这项研究中，我们探讨了在欧洲果园，苗圃和花园中与柑橘和相关属有关的Diaporthe物种的发生，多样性和致病性。调查于2015年至2016年期间在希腊，意大利，马耳他，葡萄牙和西班牙进行。从有症状的树枝，树枝和树干中分离出总共79个Diaporthe菌株。基于五个基因组位点（ITS，tef1，cal，his3和tub2）建立了多基因座系统发育，并确定了分离株的形态特征。初步致病性测试是针对柠檬，酸橙，和橙色植物，具有代表性。最常见的分离物种是D. foeniculina和D. baccae，而仅收集了四个D. novem分离株。两种新的Diaporthe物种，在此描述为D. limonicola和D. melitensis spp。十一月 被发现与柠檬植物的一种新的毁灭性死亡有关。此外，一簇无菌的Diaporthe分离株被重命名为D. infertilis。致病性测试表明，大多数柑橘属种均易受巴卡狄氏菌，foeniculina和D. novem的侵害。此外，D。limonicola和D. melitensis导致严重的溃疡病，影响了所有测试的柑橘品种。这项研究是欧洲D. baccae和D. novem关于柑橘的首次报道，也是欧洲首次发现新的Diaporthe溃疡性柑橘病。然而，没有发现柠檬酸梭菌的分离物。