The Fusarium solani species complex: ubiquitous pathogens of agricultural importance

Abstract

Members of the Fusarium solani species complex (FSSC) are capable of causing disease in many agriculturally important crops. The genomes of some of these fungi include supernumerary chromosomes that are dispensable and encode host-specific virulence factors. In addition to genomics, this review summarizes the known molecular mechanisms utilized by members of the FSSC in establishing disease.

Taxonomy: Kingdom Fungi; Phylum Ascomycota; Class Sordariomycetes; Order Hypocreales; Family Nectriaceae; Genus Fusarium.

Host range: Members of the FSSC collectively have a very broad host range, and have been subdivided previously into formae speciales. Recent phylogenetic analysis has revealed that formae speciales correspond to biologically and phylogenetically distinct species.

Disease symptoms: Typically, FSSC causes foot and/or root rot of the infected host plant, and the degree of necrosis correlates with the severity of the disease. Symptoms on above-ground portions of the plant can vary greatly depending on the specific FSSC pathogen and host plant, and the disease may manifest as wilting, stunting and chlorosis or lesions on the stem and/or leaves.

Control: Implementation of agricultural management practices, such as crop rotation and timing of planting, can reduce the risk of crop loss caused by FSSC. If available, the use of resistant varieties is another means to control disease in the field.

Useful websites: http://genome.jgi-psf.org/Necha2/Necha2.home.html.

Keywords: Fusarium solani; cell wall-degrading enzyme; conditionally dispensable; horizontal gene/chromosome transfer; phytoalexin tolerance; sudden death syndrome; supernumerary chromosome.

Figure 1

Profile and characteristics of chromosomes of the F usarium solani species complex (FSSC) 11 77‐13‐4 isolate genome. Chromosomes that contain a large number of ‘unique’ genes and in which >10% of the total number of genes were identified as potential pseudoparalogues are coloured green and red; red chromosomes have been confirmed experimentally to be dispensable. Approximate locations of genes involved in virulence are indicated.

Figure 2

The PDA1 and PEP clusters in F usarium solani species complex (FSSC) 11. The PEP cluster is ∼20 kb in size and resides on chromosome 14, a conditionally dispensable chromosome. PDA1 encodes a cytochrome P450 and PEP5 encodes a putative major facilitator superfamily (MFS) transporter. The functions of PEP1, PEP2 and cDNA3 are unknown. PDA, pisatin demethylase; PEP, pea pathogenicity.