Fusarium culmorum: causal agent of foot and root rot and head blight on wheat

Fusarium culmorum is a ubiquitous soil-borne fungus able to
cause foot and root rot and Fusarium head blight on different
small-grain cereals, in particular wheat and barley. It causes significant
yield and quality losses and results in contamination of
the grain with mycotoxins.This review summarizes recent research
activities related to F. culmorum, including studies into its population
diversity, mycotoxin biosynthesis, mechanisms of pathogenesis
and resistance, the development of diagnostic tools and
preliminary genome sequence surveys.We also propose potential
research areas that may expand our basic understanding of the
wheat–F. culmorum interaction and assist in the management of
the disease caused by this pathogen.
Taxonomy: Fusarium culmorum (W.G. Smith) Sacc. Kingdom
Fungi; Phylum Ascomycota; Subphylum Pezizomycotina; Class Sordariomycetes;
Subclass Hypocreomycetidae; Order Hypocreales;
Family Nectriaceae; Genus Fusarium.
Disease symptoms: Foot and root rot (also known as Fusarium
crown rot): seedling blight with death of the plant before or after
emergence; brown discoloration on roots and coleoptiles of the
infected seedlings; brown discoloration on subcrown internodes
and on the first two/three internodes of the main stem; tiller
abortion; formation of whiteheads with shrivelled white grains;
Fusarium head blight: prematurely bleached spikelets or blighting
of the entire head, which remains empty or contains shrunken
dark kernels.
Identification and detection: Morphological identification is
based on the shape of the macroconidia formed on sporodochia
on carnation leaf agar. The conidiophores are branched monophialides,
short and wide. The macroconidia are relatively short and
stout with an apical cell blunt or slightly papillate; the basal cell is
foot-shaped or just notched. Macroconidia are thick-walled and
curved, usually 3–5 septate, and mostly measuring 30–50 ¥ 5.0–
7.5 mm. Microconidia are absent. Oval to globose chlamydospores
are formed, intercalary in the hyphae, solitary, in chains or in
clumps; they are also formed from macroconidia.The colony grows
very rapidly (1.6–2.2 cm/day) on potato dextrose agar (PDA) at the
optimum temperature of 25 °C. The mycelium on PDA is floccose,
whitish, light yellow or red. The pigment on the reverse plate on
PDA varies from greyish-rose, carmine red or burgundy. A wide
array of polymerase chain reaction (PCR) and real-time PCR tools,
as well as complementary methods, which are summarised in the
first two tables, have been developed for the detection and/or
quantification of F. culmorum in culture and in naturally infected
plant tissue.
Host range: Fusarium culmorum has a wide range of host
plants, mainly cereals, such as wheat, barley, oats, rye, corn,
sorghum and various grasses. In addition, it has been isolated from
sugar beet, flax, carnation, bean, pea, asparagus, red clover, hop,
leeks, Norway spruce, strawberry and potato tuber. Fusarium culmorum
has also been associated with dermatitis on marram grass
planters in the Netherlands, although its role as a causal agent of
skin lesions appears questionable. It is also isolated as a symbiont
able to confer resistance to abiotic stress, and has been proposed
as a potential biocontrol agent to control the aquatic weed
Hydrilla spp.
Useful websites: http://isolate.fusariumdb.org/; http://
sppadbase.ipp.cnr.it/; http://www.broad.mit.edu/annotation/
genome/fusarium_group/MultiHome.html; http://www.fgsc.
net/Fusarium/fushome.htm; http://plantpath.psu.edu/facilities/
fusarium-research-center; http://www.phi-base.org/; http://www.
uniprot.org/; http://www.cabi.org/; http://www.indexfungorum.
org/