Yield loss study of stemphylium blight on lentil

Stemphylium blight caused by the fungal pathogen Stemphylium botryosum is a lentil disease that has become more prominent in Saskatchewan in recent years. The disease is not well studied under our growing conditions, and information is sketchy on optimal conditions for serious outbreaks of stemphylium blight, yield loss and appropriate disease management strategies. Some research has been conducted, but field trials have suffered from suboptimal experimental conditions as they were reliant on natural infection, timing of which was highly location- and year-specific. As a consequence, the critical growth stage of lentil at which infection by the pathogen negatively affects seed yield and quality remains unknown, but its determination is urgently required to decide whether and when intervention with fungicides is warranted. Similarly, screening for stemphylium blight resistance in lentil germplasm, although identified as a main breeding objective, has been hampered by the lack of a reliable field screening method.

The objectives of this 5-year project are to develop a protocol for the mass production of spores (conidia) of Stemphylium botryosum for the purpose of controlled inoculations; to conduct replicated field experiments to determine yield loss through stemphylium blight, using the tunnel system evaluated in the pilot study and the spore inoculum developed under (1); and to evaluate and optimize the use of tunnels and spore inoculation for resistance screening of lentil germplasm to stemphylium blight. This project will benefit the Saskatchewan agricultural industry in two ways: Firstly, the development of a protocol for spore production will allow us to conduct yield loss studies in lentil under field conditions. Through these experiments we will be able to determine whether and at what stage infestations of lentil with stemphylium blight causes economic loss. Based on the results, we will be able to develop recommendations for lentil producers on the management requirements of stemphylium blight. These recommendations are expected to reduce cost to lentil producers by eliminating unnecessary fungicide applications targeted at stemphylium blight or optimizing applications. Secondly, evaluation of the field screening method will facilitate the development of lentil germplasm with higher levels of resistance as it will allow us to establish a stemphylium blight disease nursery in the field to routinely screen lentil breeding material for higher resistance to the pathogen.