New Disease Reports
New Disease Reports (2002) 6, 3.
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First report of Exserohilum pedicellatum on Zea mays in Australia

R.L. Gilbert

*ross.gilbert@agric.nsw.gov.au

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Accepted: 22 Aug 2002

During routine investigation of a cob-rot outbreak in the central west of New South Wales, diseased roots of mature sweetcorn (Zea mays L.) cv. 'Golden Millennium' were sampled. Symptomatic adventitious roots exhibited a dark brown root rot extending from the tip. Exserohilum pedicellatum (Henry) Leonard & Suggs, the anamorph of Setosphaeria pedicellata (Nelson) Leonard & Suggs was isolated from the diseased material (DAR75790). Morphology agreed with the description of Sivanesan (1987) and conidia measured 56-95 µm (av. 72.5 µm) long by 21-32 µm (av. 27µm) wide with a length:breadth (L/B) ratio of 2.76.

Sweetcorn seedlings cv. 'Golden Millennium' were inoculated at the 3-leaf stage with a conidial suspension of DAR75790. After incubation, E. pedicellatum was recovered from brown lesions on seminal and adventitious roots of inoculated plants. No above ground symptoms were evident and root symptoms were mild.

Hosts of E. pedicellatum are listed in Sivanesan (1987) as Echinochloa, Oryza, Paspalum, Setaria, Sorghum and Triticum, where it is associated with dark brown root lesions, and Zea, where it causes a root rot. Sivanesan (1987) listed the distribution of E. pedicellatum as Egypt, India, Pakistan, South Africa and the USA. No later published records exist for Australia. A review of current unpublished Australian checklists and herbarium databases list records on Oryza, Sorghum, Triticum and soil collected over a period from 1976 to 1985 but apparently without formal publication. No unpublished Australian records on Zea were revealed. Australian isolates from Triticum (DAR27966c) collected in 1976 and Sorghum (DAR29011a) collected in 1977, were examined by the author and confirmed as E. pedicellatum. Conidial dimensions of the Sorghum isolate were similar to DAR 75790 however the Triticum isolate had an average length of 91 µm and a L/B ratio of 3.38.

Although in Australia, E. pedicellatum has not been detected previously on Zea, in light of the herbarium records on other hosts, it has probably existed as a minor pathogen in this country for many years. This is the first published record of E. pedicellatum on Zea mays in Australia and on any host in this country.

Figure1+
Figure 1: Figure1. Conidia of Exserohilum pedicellatum DAR75790 from Zea mays cv. 'Golden Millennium'. Magnification x400.
Figure 1: Figure1. Conidia of Exserohilum pedicellatum DAR75790 from Zea mays cv. 'Golden Millennium'. Magnification x400.
Figure2+
Figure 2: Figure2. Zea mays cv. 'Golden Millennium'. Left - Inoculated with Exserohilum pedicellatum DAR75790. The fungus was recovered from the discoloured seminal and adventitious roots. Only isolates of Fusarium moniliforme Sheldon were recovered from lesions on the mesocotyl. Right - Noninoculated control plant.
Figure 2: Figure2. Zea mays cv. 'Golden Millennium'. Left - Inoculated with Exserohilum pedicellatum DAR75790. The fungus was recovered from the discoloured seminal and adventitious roots. Only isolates of Fusarium moniliforme Sheldon were recovered from lesions on the mesocotyl. Right - Noninoculated control plant.

References

  1. Sivanesan A, 1987. Graminicolous Species of Bipolaris, Curvularia, Drechslera, Exserohilum and their Teleomorphs. Mycological Papers No. 158, CAB International, Wallingford, UK.
This report was formally published in Plant Pathology

©2002 The Authors