F. pseudograminearum O’Donnell et. T. Aoki sp. nov.
Gibberella zeae (Schwein.) Petch [teleomorph]
F. graminearum Schwabe, Group II [anamorph]
G. avenacea R.J. Cook [teleomorph]
F. avenaceum (Fr.:Fr.) Sacc. [anamorph]
F. culmorum (W.G. Smith) Sacc.
- Symptoms: The crown rot fungus will cause whiteheads through necrosis of the crown and lower stem, causing premature senescence. These whiteheads can have no grain, pinched grain, or normal grain, depending upon the development of crown rot in relation to crop maturity (picture below).Under humid conditions, the fungus can cause pink pigmentation in the crown and lower leaf sheath. Browning of the lower stem is another fairly common symptom, but becomes less obvious in wet seasons.
- Development: The fungus persists as hyphae in stem residues either on the soil surface or mixed into the soil. Fusarium infects wheat through the crown or lower leaf sheaths in no-tillage systems, but when infested residues are present in the soil, the fungi infects through the sub-crown internode or crown. It is believed that the fungi infect through hyphal growth directly in contact with the plant tissue. Following the infection, the fungi colonize the lower stem region to the 3rd or 4th node. Infection is favored by warm, moist soil conditions, and colonization of the plan is favored by warm, dry conditions where the plants are under moisture stress.
- Hosts/Distribution: Fusarium can occur in all winter cereals, and a wide range of pasture grasses and grass weeds. Crown rot has been reported in Australia, USA, South Africa, New Zealand, Italy, Morocco, Syria and Turkey. F. pseudograminarium is most prevalent in areas where spring wheat is grown in winter under mild temperatures, and then ripens under hot, dry conditions. F. culmorum is favored under similar conditions, but appears more common in cooler conditions. Most current varieties of wheat are susceptible to the fungi, though partial resistance will occur.
- Importance: Crown rot is a wide-spread fungus which causes considerable yield losses, with losses exceeding 80% in individual crops, especially in systems where tillage has been reduced and cereals are grown in close rotation.
References:
- Professor Lester Burgess- Head, Fusarium Research, University of Sydney, Australia.
- Dr. Hugh Wallwork- Senior Plant Pathologist, South Australian Research Development Institute, Adelaide, Australia.
- Dr. Alison R. Bentley- former PhD student on Fusarium Crown Rot from the University of Sydney, Australia. Now working for NIAB, United Kingdom.