Molecular techniques for studying <i>Fusarium</i> ear blight of wheat

This work has compared polymerase chain reaction (PCR) assays and traditional visual disease assessment to evaluate the severity of <i>Fusarium</i> ear blight (FEB) ofwheat under field and glasshouse conditions. In a field trial, PCR analysis highlighted the problem of diagnosis of FEB of wheat based on visual disease assessment where natural inoculum was present. PCR-based analysis detected <i>F. poae</i> predominantly in the glumes and <i>Microdochium nivale</i> sub-species were predominantly found in the rachis component of ears. <i>M. nivale</i> var. <i>majus</i> was more frequently observed than var. nivale (64 and 36 %, respectively). <br></br><br></br> Quantitative PCR analysis and conventional visual disease assessment were used to evaluate fungicide efficacy against FEB of wheat caused by <i>F. culmorum</i> and <i>F. poae</i> in three glasshouse trials (1994/5-1996/7). Prochloraz and tebuconazole significantly decreased both visual symptoms of FEB and fungal DNA content of <i>F. culmorum</i> and <i>F. poae</i> ear blight of wheat. Overall, both fungicides appeared equally effective, although the efficacy ofthese fungicides was consistently greater as measured by PCR analysis rather than by visual disease assessment. Inoculation with <i>F. culmorum</i> significantly reduced yield (1000 grain weight) whereas inoculation with F. poae had no significant effect on yield. <br></br><br></br> <i>Fusarium culmorum</i> was successfully transformed with the GUS reporter gene. GUS activity levels of transformants varied, but transformation did not affect pathogenicity on wheat seedlings. A GUS transformant was used to study the effectiveness of two fungicides against <i>F. culmorum</i> foot rot of wheat. <br></br><br></br> Primers to the Tri5 gene were used to develop a PCR-based assay for the specific detection of potential trichothecene-producing <i>Fusarium</i> species. These primers were also used to develop an RT-PCR-based assay for the detection and semiquantification of <i>F. culmorum Tri5</i> gene expression 'relative to p-tubulin gene expression' in RNA extracts from <i>F. culmorum</i>. This assay was used to show that time and fungicides can affect <i>Tri5</i> gene expression in liquid culture.

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

The Open University

Year dc:date.issued

1998

Author dc:creator

• Doohan, Fiona Maria

Language dc:language

en