Understanding how Sclerotinia sclerotiorum initiates stem rot: factors affecting the germination of sclerotia

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Series Number

DAW00228, UM00051




Under laboratory conditions germination of sclerotia of Sclerotinia sclerotiorum was favoured by a night/day temperature of 10/20°C. None germinated at a higher night/day temperature of 16/29°C and exposure to this high temperature reduced the ability of sclerotia to subsequently germinate when they were moved to a 10/20°C night/day temperature. Understanding the temperatures that favour germination of sclerotia can assist with identifying the potential period in which ascospores may be produced in a given location. In an average year, and assuming sufficient moisture is available, this is likely to be May-October in cooler climates like Esperance, and June-September in warmer climates like Mingenew. Whether this period overlaps with the flowering window of canola crops will determine the risk of stem rot developing in a given season. Under a favourable night/day temperature of 10/20°C and ongoing moisture conditions, sclerotia germinated and many produced multiple apothecia (small mushroom like structures) at a time. Some sclerotia were able to produce additional apothecia subsequent to the ones produced when they first germinated and these survived from two to five weeks each over a three month period. This research shows that if favourable weather conditions persist, a steady production of ascospores can be released from one sclerote over several months. Some sclerotia were able to produce additional apothecia subsequent to the ones produced when they first germinated. Sclerotia that were ground to simulate the effects of seed destructor technology were still able to germinate under laboratory conditions. Apothecia produced from ground up sclerotia were smaller than those produced from intact sclerotia. Turning the sclerotia into a ‘flour’ (< 0.5mm), however, significantly reduced and delayed germination.


Agronomy and Crop Sciences | Biosecurity