An expanded concept of <i>Ceratocystis manginecans</i> and five new species in the Latin American clade of <i>Ceratocystis</i>

The genus <i>Ceratocystis</i> contains a number of emerging plant pathogens, mostly members of the Latin American Clade (LAC), in which there are several unresolved taxonomic controversies. Among the most important are Brazilian pathogens in the <i>C. fimbriata</i> complex, <i>C. manginecans</i> and <i>C. eucalypticola</i>. Representatives of <i>C. manginecans</i> and <i>C. eucalypticola</i> from India and China, respectively, were shown to be fully interfertile in laboratory matings, and hybrids between the putative species were identified on <i>Punica</i> in India. An Indian tester strain was sexually compatible with representatives of what has been considered <i>C. fimbriata</i> on numerous hosts across Brazil. In this revision of the LAC, the name <i>C. fimbriata</i> is restricted to the widely dispersed <i>Ipomoea</i> strain, and <i>C. manginecans</i> is recognized as a Brazilian species that is important on <i>Mangifera, Eucalyptus</i>, and many other crops. <i>C. mangivora</i> and <i>C. mangicola</i> are also considered synonyms of <i>C. manginecans</i>. Based on phylogenetics and mating studies, two other Brazilian species are recognized: <i>C. atlantica</i>, sp. nov., and <i>C. alfenasii</i>, sp. nov., each with wide host ranges. Three new Caribbean species are recognized based on phylogenetics and earlier inoculation studies: <i>C. costaricensis</i>, sp. nov., on <i>Coffea, C. cubensis</i>, sp. nov., on <i>Spathodea</i>, and <i>C. xanthosomatis</i>, sp. nov., on the vegetatively propagated aroids <i>Xanthosoma</i> and <i>Syngonium</i>. Some of the other <i>Ceratocystis</i> species were based primarily on unique internal transcribed spacer (ITS) rDNA sequences, but the unreliability of rDNA sequences was demonstrated when intraspecific crossing of isolates with differing ITS sequences generated single-ascospore progeny with intragenomic variation in ITS sequences and others with new ITS sequences. Species recognition in <i>Ceratocystis</i> should use phenotype, including intersterility tests, to help identify which lineages are species. Although some species remain under-studied, we recognize 16 species in the LAC, all believed to be native to Latin America, the Caribbean region, or eastern USA.

长喙壳属（Ceratocystis）包含多个新兴植物病原菌类群，其中多数隶属于拉丁美洲演化支（Latin American Clade, LAC），该演化支内尚存多项未决的分类学争议。其中最为关键的类群包括巴西境内隶属于纤细长喙壳（C. fimbriata）复合群、芒果长喙壳（C. manginecans）以及桉长喙壳（C. eucalypticola）的病原菌。分别来自印度与中国的芒果长喙壳与桉长喙壳菌株经实验室交配实验证实可完全性亲和，且在印度的石榴属（Punica）植物上已鉴定出这两个推定物种间的杂交子代。一份印度的测试菌株与巴西境内多种寄主上的纤细长喙壳类群均具有性亲和性。在本次拉丁美洲演化支的分类修订中，纤细长喙壳这一名称被限定于广泛分布的牵牛属（Ipomoea）菌株，而芒果长喙壳被认定为巴西本土物种，其寄主范围涵盖芒果属（Mangifera）、桉属（Eucalyptus）及诸多其他作物。食芒果长喙壳（C. mangivora）与芒果栖长喙壳（C. mangicola）均被视为芒果长喙壳的同物异名。基于系统发育学与交配研究结果，本次修订还确认了另外两个巴西本土物种：新种大西洋长喙壳（C. atlantica, sp. nov.）与阿尔芬斯长喙壳（C. alfenasii, sp. nov.），二者均具有宽泛的寄主范围。依据系统发育学数据与此前的接种实验研究，本次修订还认定了3个加勒比海地区新物种：寄生于咖啡属（Coffea）的哥斯达黎加长喙壳（C. costaricensis, sp. nov.）、寄生于火焰木属（Spathodea）的古巴长喙壳（C. cubensis, sp. nov.），以及寄生于无性繁殖天南星科植物黄肉芋属（Xanthosoma）和合果芋属（Syngonium）的黄肉芋长喙壳（C. xanthosomatis, sp. nov.）。部分其他长喙壳属物种的界定主要基于独特的内部转录间隔区（internal transcribed spacer, ITS）核糖体DNA（rDNA）序列，但已有研究证实rDNA序列的可靠性不足：当对ITS序列存在差异的菌株进行种内交配时，其单子囊孢子子代的基因组内存在ITS序列变异，部分子代甚至产生了全新的ITS序列。长喙壳属的物种界定应结合表型特征（包括互交不育测试），以辅助确定哪些演化支可被认定为独立物种。尽管部分物种的研究仍不够充分，但本次修订共认定拉丁美洲演化支内的16个物种，所有物种均被认为起源于拉丁美洲、加勒比海地区或美国东部。