Controlling Fusarium Head Blight in oat

Oats (Avena sativa) is a versatile crop grown worldwide for animal feed and human consumption. Humanoat consumption has recently risen due to its various health benefits. However, oats are susceptible toFusarium head blight (FHB) caused by various Fusarium fungi. FHB reduces yield and leads to mycotoxinaccumulation. The most commonly reported mycotoxins in oat are trichothecenes deoxynivalenol (DON)and T-2/HT-2 toxins. Trichothecenes inhibit eukaryotic protein biosynthesis and cause acute and chronictoxicoses in human and animals. Effective control of FHB is important for ensuring safety and quality ofoats. This thesis examines various aspects of FHB in oats, relevant to the development of better FHBcontrol strategies.Accurate FHB symptom identification is crucial for breeding resistant oats, but the symptoms of FHB arecryptic, causing errors in scoring the disease during trials. This work presents an affordable method forassessing FHB symptoms in oats by de-hulling mature seeds. Symptoms of blackening and discolorationof the oat kernels significantly correlate with Fusarium DNA and mycotoxin accumulation and thus canbe used as quantitative disease indicators.To enhance pathogen resistance, identifying and characterizing plant resistance genes is key. In thiswork two oat genes coding for DON-detoxifying UDP-glucosyltransferases (UGTs) were identified andcharacterised. Transcripts of two oat UGTs were highly upregulated in response to DON treatment andF.graminearum infection. The genes conferred resistance to several trichothecenes when expressed inyeast. Both UGTs, recombinantly expressed in E.coli were confirmed for their ability to detoxify DON.These genes could potentially be used for developing genetic markers for FHB resistance in oat.Further in this thesis, biocontrol possibilities for FHB in oats are investigated. The fungal BCAClonostachys rosea's potential against FHB is examined. Treating oat spikelets with C. rosea reducedFusarium DNA and DON content in mature kernels. C.rosea enhanced both rate of DON detoxificationand expression of DON-detoxifying UGTs. Furthermore, there was significant upregulation of markers ofinduced resistance, including PR proteins and the WRKY23 transcription factor, indicating that thebiocontrol effect of C. rosea is attributed to the induction of plant defences.Additionally, oats' own endophytes were explored for FHB biocontrol. Fungal endophytes from oatspikelets were isolated and tested for reducing FHB in greenhouse trials. The most successful isolatePseudozyma flocculosa significantly reduced FHB symptoms, F. graminearum biomass, and DONaccumulation in oat. Treatment of oat with P. flocculosa induced expression of genes encoding for PRproteins, known to be involved in FHB resistance