Assessment of infection by Fusarium Pseudograminearum in wheat seedling tissues using quantitative PCR and a visual discoloration scale

Knight, Noel L. and Sutherland, Mark W. and Martin, Anke and Herde, Damian J. (2012) Assessment of infection by Fusarium Pseudograminearum in wheat seedling tissues using quantitative PCR and a visual discoloration scale. Plant Disease, 96 (11). pp. 1661-1669. ISSN 0191-2917


Assessment among cereal genotypes of relative seedling resistance to the crown rot pathogen Fusarium pseudograminearum has been primarily based on visual discoloration of the leaf sheaths. This study is the first to investigate the relationship between the widely used visual rating of seedling leaf sheath discoloration and the degree of colonization of these tissues by the pathogen, based on quantitative polymerase chain reaction (qPCR) of fungal DNA using primers specific for the translation elongation factor α sequence. Fourteen-day-old seedlings of four hard white spring wheat genotypes which differ in their degree of resistance to the pathogen, based on the expression of visible symptoms, were inoculated using a droplet method and assessed weekly from 7 to 35 days after inoculation (dai) for both discoloration and fungal DNA content per unit of tissue weight. Both visual assessment of disease symptoms and qPCR of fungal biomass indicated significant differences between the partially resistant and susceptible wheat genotypes from 14 dai. Visual discoloration of leaf sheath tissues was strongly correlated with fungal biomass estimated
by qPCR in all four genotypes; however, this correlation became
weaker with increasing time after inoculation. Significant correlations between these parameters were indicated at 14, 21, and 28 dai whereas,by 35 dai, the correlation was not significant. Evaluation of plants at 14 dai provided a rapid test which gave clear discrimination between lines for both parameters and was the time point of closest correlation between fungal colonization and disease symptoms. Symptom expression at all times following inoculation was accompanied by tissue infection, and at no time was symptomless infection observed under this screening environment. These qPCR results confirm that visual assessments of disease symptoms reflect the extent of tissue colonization by the pathogen in recently colonized tissues and confirm the validity of visual assessments for disease rating in high-throughput screening of breeding materials.

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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Permanent restricted access to published version due to publisher copyright policy.
Faculty / Department / School: Historic - Faculty of Sciences - No Department
Date Deposited: 21 Dec 2012 11:49
Last Modified: 18 Aug 2014 23:24
Uncontrolled Keywords: Fusarium pseudograminearum; crown rot; leaf sheath discoloration
Fields of Research : 07 Agricultural and Veterinary Sciences > 0703 Crop and Pasture Production > 070308 Crop and Pasture Protection (Pests, Diseases and Weeds)
Socio-Economic Objective: D Environment > 96 Environment > 9604 Control of Pests, Diseases and Exotic Species > 960413 Control of Plant Pests, Diseases and Exotic Species in Farmland, Arable Cropland and Permanent Cropland Environments
Identification Number or DOI: 10.1094/PDIS-12-11-1050-RE

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