Host resistance: the key to effectively manage Sclerotinia stem rot (Sclerotinia sclerotiorum) in canola (Brassica napus)
Muhammad Azam Khan: School of Agriculture and Environment Faculty of Science The University of Western Australia
<div>Recent decades have seen increased areas sown to canola (<em>Brassica napus</em>) and associated changes in fungal disease incidence and/or severity of canola disease epidemics across Australia. One of the most devastating diseases of canola is caused by the fungal pathogen, <em>Sclerotinia sclerotiorum</em>. To manage this pathogen cost-effectively for the long term, it is essential to locate, develop and deploy new and effective host resistances in order to protect and ensure economic canola yields. However, while some high level resistance has been located in historic cultivars no longer available and also across a range of diverse Brassicaceae species, currently there are no commercial canola cultivars in Australia targeting resistance to Sclerotinia stem rot. To address this, cohorts of canola genotypes consisting of parents with known resistance to Sclerotinia stem rot and their succeeding generations are being evaluated for resistance against <em>S. sclerotiorum</em>. Phenotypic variation occurred among segregating populations at seedling and adult stages, ranging from highly resistant to susceptible types. Close relationships between phenotypic expressions of host resistance within and between segregating populations were identified under both controlled and field environments. Phenotypic selection in F<sub>2 </sub>and F<sub>3</sub> coupled with QTL mapping in F<sub>2 </sub>genotypes is being utilized to define the basis of genetic control of resistance against this pathogen in canola. These outcomes will be of critical value to plant breeders in developing new cultivars with improved resistance against this major disease of canola both within Australia and worldwide.</div>
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