New Disease Reports (2013) 27, 22. [http://dx.doi.org/10.5197/j.2044-0588.2013.027.022]
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Rhizoctonia solani AG3-PT infecting maize stem bases and roots in the United Kingdom

A.W. McCormack 1,2, J.W. Woodhall 1*, M.A. Back 2 and J.C. Peters 1

*james.woodhall@fera.gsi.gov.uk

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Received: 13 Mar 2013; Published: 18 Jun 2013

Keywords: soil DNA, alternative host, potato

Rhizoctonia solani is an important pathogen of potatoes. The fungus is comprised of 13 anastomosis groups (AGs) of which AG3-PT (the potato subgroup) is most closely associated with potatoes (Tsror, 2010). Maize plants (cv. Ballade) and soil were sampled from a maize field in Shropshire in June 2012. Brown lesions were observed on the roots and stem bases of four plants. From one affected plant, pure Rhizoctonia solani cultures were obtained as described in Woodhall et al. (2007). These were identified as AG3-PT using real-time PCR (Woodhall et al., 2013).

A controlled environment experiment was undertaken to satisfy Koch’s postulates. The isolate was grown on potato dextrose agar at 20°C in 100 mm diameter petri dishes. After two weeks, six fully colonised plates were macerated using a scalpel and added to 1 kg of silver sand. Fifty grams of this mixture was mixed with 450 g of John Innes No. 2 and added to each pot. Three, one-week-old, maize seedlings (cv. Sweet Nugget) were transferred into the inoculated compost. Maize seedlings were also transferred to non-inoculated pots. Each treatment was replicated five times. Pots were placed in a controlled environment room (ambient humidity and 12h/12h light/dark photoperiod) at 8°C for two weeks, to simulate conditions at planting. After two weeks, the temperature was raised to 20°C. The plants were allowed to grow for a further three weeks, after which they were washed and assessed for disease. Stem base browning was observed in nine of the 15 plants inoculated. No browning was observed on any of the non-inoculated control plants. Twenty pieces of plant material with symptoms were plated on 2% tap water agar, from which AG3-PT (as confirmed by real-time PCR) was re-isolated from 50% of attempted isolations, thereby satisfying Koch’s postulates.

Quantification of AG3-PT (using real-time PCR) from soil samples taken from the site in Shropshire revealed a potential interaction between maize and AG3-PT. Soil was taken from nine 30 m2 plots over the field, one plot including the affected maize plants. DNA was extracted from 250 g of soil as described in Woodhall et al. (2012). In soil taken from the same plot as the affected maize plants, levels of AG3-PT DNA were determined to be 3501 pg DNA/g soil. In the other eight plots levels of AG3-PT were determined to be 40 pg DNA/g soil (range 0 to 183, SD = 74). Levels of AG3-PT in soil were therefore higher in the area of the affected maize plants.

To the authors’ knowledge, this is the first report of AG3-PT infecting maize in the UK. AG3-PT has only been found previously in the UK on potatoes (Woodhall et al., 2007) but has been found in several crop and weed hosts worldwide (Tsror, 2010). In pathogenicity tests, maize has been found to be susceptible to AG3 infection along with other cereal crops such as wheat and oats (Carling et al., 1986). In this study, soil levels of AG3-PT appear to increase within the vicinity of infected maize plants; therefore maize may provide a suitable alternative host for R. solani (AG3-PT) and potentially increase the risk of disease in subsequent potato crops.

Acknowledgements

Alex McCormack acknowledges support from the BSPP Undergraduate Vacation Bursary Scheme.


References

  1. Carling DE, Leiner RH, Kebler KM, 1986. Characterisation of Rhizoctonia solani and binucleate Rhizoctonia-like fungi collected from Alaskan soils with varied crop histories. Canadian Journal of Plant Pathology 8, 305-310. [http://dx.doi.org/10.1080/07060668609501804]
  2. Tsror LJ, 2010. Biology, epidemiology and management of Rhizoctonia solani on Potato. Journal of Phytopathology 158, 649-658. [http://dx.doi.org/10.1111/j.1439-0434.2010.01671.x]
  3. Woodhall JW, Adams IP, Peters JC, Harper G, Boonham N, 2013. A new quantitative real-time PCR assay for Rhizoctonia solani AG3-PT and the detection of AGs of Rhizoctonia solaniassociated with potato in soil and tuber samples in Great Britain. European Journal of Plant Pathology 136, 273-280. [http://dx.doi.org/10.1007/s10658-012-0161-8]
  4. Woodhall JW, Lees AK, Edwards SG, Jenkinson P, 2007. Characterization of Rhizoctonia solani from potato in Great Britain. Plant Pathology 56, 286-295. [http://dx.doi.org/10.1111/j.1365-3059.2006.01545.x]
  5. Woodhall JW, Webb KM, Giltrap PM, Adams IP, Peters JC, Budge GE, Boonham N, 2012. A new large scale soil DNA extraction procedure and real-time PCR assay for the detection of Sclerotium cepivorum in soil. European Journal of Plant Pathology 134, 467-473. [http://dx.doi.org/10.1007/s10658-012-0025-2]

To cite this report: McCormack AW, Woodhall JW, Back MA, Peters JC, 2013. Rhizoctonia solani AG3-PT infecting maize stem bases and roots in the United Kingdom. New Disease Reports 27, 22. [http://dx.doi.org/10.5197/j.2044-0588.2013.027.022]

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