The phoma-like dilemma

Abstract

Species of <i>Didymellaceae</i> have a cosmopolitan distribution and are geographically widespread, occurring in diverse ecosystems. The family includes several important plant pathogenic fungi associated with fruit, leaf, stem and root diseases on a wide variety of hosts, as well as endophytic, saprobic and clinically relevant species. The <i>Didymellaceae</i> was recently revised based on morphological and phylogenetic analyses of ex-type strains subjected to DNA sequencing of partial gene data of the LSU, ITS, <i>rpb2</i> and <i>tub2</i> loci. Several poly- and paraphyletic genera, including <i>Ascochyta</i>, <i>Didymella</i> and <i>Phoma</i> were redefined, along with the introduction of new genera. In the present study, a global collection of 1 124 <i>Didymellaceae</i> strains from 92 countries, 121 plant families and 55 other substrates, including air, coral, human tissues, house dust, fungi, insects, soil, and water were examined via multi-locus phylogenetic analyses and detailed morphological comparisons, representing the broadest sampling of <i>Didymellaceae</i> to date. Among these, 97 isolates representing seven new genera, 40 new species and 21 new combinations were newly introduced in <i>Didymellaceae</i>. In addition, six epitypes and six neotypes were designated to stabilise the taxonomy and use of older names. A robust, multi-locus reference phylogenetic tree of <i>Didymellaceae</i> was generated. In addition, <i>rpb2</i> was revealed as the most effective locus for the identification of <i>Didymellaceae</i> at species level, and is proposed as a secondary DNA marker for the family.