April 29, 2005
Source: British Society for Plant Pathology, New Disease Reports, Vol. 11 [edited]
<http://www.bspp.org.uk/ndr/july2005/2005-39.asp>

First report of Bipolaris sacchari causing wheat stem-base disease in Iran
M.J. Soleimani <agrms@basu.ac.ir> and S. Kazemi, Dept. of Plant Protection, College of Agriculture, Bu-Ali Sina University, Hamadan, Iran. Accepted for publication 26 Apr 2005.

During May and June of 2003, wheat plants in several fields in Hamada, Iran showed symptoms of root rot and crown necrosis.

Stem-base and root samples were submerged in 0.5 percent sodium hypochlorite for 3-5 min., rinsed with sterile distilled water, transferred to Petri dishes containing PDA, and incubated at 22-25 deg C for 1 week. _Bipolaris_ spp. was the most prevalent fungus isolated. Based on the host origin, conidia and conidiophore morphology, number of pseudosepta and hilum characteristics, the pathogen was identified as _Bipolaris sacchari_ (Sivanesan, 1987).

Inoculum for pathogenicity tests was produced by seeding 200 g of sterile wheat stubble in an Erlenmeyer flask with 4 mycelial plugs 5 mm in diameter from 5-day old fungal colonies grown on agar medium, and incubating at room temperature for 3 weeks. The inoculated wheat straw was incorporated into sterile soil (1 percent w/w), transferred to 5 pots (25-cm) and planted with 8 wheat seeds per pot. Control plants were grown in soil containing 1 percent sterile wheat straw. The treatments were replicated 5 times. Plants were grown in a greenhouse for 75 days at 24 deg C, then scored for disease (Singleton et al, 1992).

Symptoms were similar to those observed in the field and no disease was found in the control plants. The fungus was re-isolated from the infected parts. In a separate study using wheat cultivars 'Alvand' and 'Roushan', the pathogen caused a significant reduction on seed germination and plant height.

To our knowledge, this is the 1st detailed report of root and stem rot disease of wheat caused by _B. sacchari_ in Iran. Further field studies are needed on the ecology and pathogenicity of _B. sacchari_ to formulate steps for controlling root and stem rot of wheat.

References

Singleton LL, Mihail JD, Rush CM, 1992. Methods for Research on Soil-borne Phytopathogenic Fungi. St Paul, MN., USA: APS Press.

Sivanesan A, 1987. Graminicolus Species of Bipolaris, Curvularia, Drechslera, Exserohilum and their teleomorphs. Mycological Paper No 158, Wallingford, UK: CAB International.

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[There does appear to be much literature on _Bipolaris sacchari_. Bs infects sugarcane, causing eye spot disease. A related species, _B. sorokiniana_ (teleomorph _Cochliobolus sativus_) is the causal agent of common root rot, leaf spot disease, seedling blight, head blight, and black point of wheat and barley. That fungus is one of the most serious foliar disease constraints for both crops in warmer growing areas and causes significant yield losses. High temperature and high relative humidity favour the outbreak of the disease, in particular in South Asia's intensive irrigated wheat-rice production systems. In general, disease management would involve use of approved seed treatment, plowing down of crop residues, and several years of rotation to non-cereal crops. - Mod.DH]