Diagnosis and control of foot rot pathogens of wheat

Foot rot disease of wheat is caused by the pathogens <i>Fusarium culmorum, F. avenaceum</i> and <i>Microdochium nivale</i>. Symptoms of foot rot are a general browning of the stem base and leaf sheath. There is a discrepancy between the ability of fungicides to control these pathogens <i>in vivo</i> and <i>in vitro</i>, and no relationship between disease symptom severity and yield loss has been established in wheat. The identification of the causal agents of foot rot disease is not possible from examination of disease symptoms alone. <br></br><br></br>This work showed that the azole fungicides flusilazole and prochloraz inhibited the germination of conidia and mycelial growth of <i>F. culmorum</i>, <i>F. avenaceum</i> and <i>M. nivale in vitro</i> to a varying extent. However, no consistent control of these pathogens in wheat was observed in the field using the same fungicides. Further studies employing a semicontrolled outdoor experiment showed a relationship between density and timing of inoculum application, disease symptom severity and yield loss in wheat artificially inoculated with <i>F. culmorum</i> and <i>M. nivale</i>. <br></br><br></br>Molecular marker systems were used to address the problem of pathogen detection and identification. A Random Amplified Polymorphic DNA (RAPD) assay was developed to differentiate <i>F. culmorum</i>, <i>F. avenaceum</i> and two types of<i>M. nivale</i> (<i>M. nivale</i> var.<i>nivale</i> and <i>M. nivale</i> var.<i>majus in vitro</i>. Selected RAPD products were cloned and sequenced and species specific primers constructed from this sequence information. These primers were used in the polymerase chain reaction (peR) and were shown to detect the pathogens in host tissue. This technique was adapted by addition of a competitor fragment to the peR reaction resulting in a quantifiable competitive peR assay. Using this method the fungal biomass of each pathogen present in the host tissue could be estimated. The development of these techniques for the identification, detection and quantification of <i>F. culmorum</i>, <i>F. avenaceum</i>, <i>M. nivale</i> var.<i>nivale</i> and <i>M. nivale</i> var. <i>majus</i> in plant tissue will allow more extensive studies of the epidemiology of these species, the competition between species and the effect of fungicides on these pathogens can be carried out.

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

The Open University

Year dc:date.issued

1996

Author dc:creator

• Lees, Alison Kathryn

Language dc:language

en