One fungus, one name promotes progressive plant pathology

Abstract

The robust and reliable identification of fungi underpins virtually every element of plant pathology, from disease diagnosis to studies of biology, management/control, quarantine and, even more recently, comparative genomics. Most plant diseases are caused by fungi, typically pleomorphic organisms, for which the taxonomy and, in particular, a dual nomenclature system have frustrated and confused practitioners of plant pathology. The emergence of DNA sequencing has revealed cryptic taxa and revolutionized our understanding of relationships in the fungi. The impacts on plant pathology at every level are already immense and will continue to grow rapidly as new DNA sequencing technologies continue to emerge. DNA sequence comparisons, used to resolve a dual nomenclature problem for the first time only 19 years ago, have made it possible to approach a natural classification for the fungi and to abandon the confusing dual nomenclature system. The journey to a one fungus, one name taxonomic reality has been long and arduous, but its time has come. This will inevitably have a positive impact on plant pathology, plant pathologists and future students of this hugely important discipline on which the world depends for food security and plant health in general. This contemporary review highlights the problems of a dual nomenclature, especially its impact on plant pathogenic fungi, and charts the road to a one fungus, one name system that is rapidly drawing near.

Figure 1

Symptoms of diseases caused by fungi belonging to the groups illustrated in the phylogenetic trees (Fig. 2) and where a single genus name (alternatives in parentheses) will simplify many aspects of dealing with them. (A) Diaporthe rhusicola (Phomopsis) leaf spot on Rhus pendulina. (B) Leaf disease caused by Teratosphaeria (Kirramyces) cryptica on Eucalyptus sp. (C) Ramularia lamii (Mycosphaerella) leaf spot on Leonotus leonurus. (D) Black pod rot on peanut caused by Calonectria illicicola (Cylindrocladium). (E) Streaked discoloration of Platanus wood caused by Ceratocystis platani (Thielaviopsis). (F) Neofusicoccum protearum (Botryosphaeria) canker on Protea sp.

Figure 2

Phylogenetic trees for selected species of the plant pathogenic genera (following strict priority): (A) Calonectria; (B) Diaporthe; (C) Neofusicoccum; (D) Teratosphaeria; (E) Ceratocystis; (F) Grossmania. Trees were constructed using neighbour‐joining analysis with HKY85 as substitution model in PAUP version 4.0b10. Teleomorph names in the trees are shown in blue and anamorph names in green. Basionyms are presented in either blue or green in parentheses, and GenBank accession numbers are in black in parentheses. The single name highlighted in the right‐hand column for each species presents the name that will probably be used for the fungi following the ‘one fungus, one name’ approach. Bootstrap support values are based on 1000 replicates and the scale bar indicates the number of substitutions per site. ITS, internal transcribed spacer.

Figure 2

Phylogenetic trees for selected species of the plant pathogenic genera (following strict priority): (A) Calonectria; (B) Diaporthe; (C) Neofusicoccum; (D) Teratosphaeria; (E) Ceratocystis; (F) Grossmania. Trees were constructed using neighbour‐joining analysis with HKY85 as substitution model in PAUP version 4.0b10. Teleomorph names in the trees are shown in blue and anamorph names in green. Basionyms are presented in either blue or green in parentheses, and GenBank accession numbers are in black in parentheses. The single name highlighted in the right‐hand column for each species presents the name that will probably be used for the fungi following the ‘one fungus, one name’ approach. Bootstrap support values are based on 1000 replicates and the scale bar indicates the number of substitutions per site. ITS, internal transcribed spacer.