Soil-borne disease in poor persistence of pastures: Identification of causal agents

The role of soil-borne disease in the poor persistence of pastures in northern Aotearoa/New Zealand - Identification of causal agents

Globally, soil-borne plant diseases negatively impact the productivity and persistence of agricultural systems and pastures in Aotearoa/New Zealand (AoNZ) are no exception. In recent decades, there have been repeated observations of poor persistence of sown pastures in northern AoNZ(1). Economic modelling suggests that soil disease of the dominant pasture plants in this country, Lolium perenne (perennial ryegrass) and Trifolium repens (white clover), is responsible for a $909 ha-1 year-1 reduction in Waikato pasture-based farm profitability(2). Research into possible causative agents of soil disease in pastures was primarily conducted in the 1980s to early 2000s(3) when pasture management and climate were much different to the present day. Common plant pathogenic fungi including Fusarium spp., Pythium spp., and Rhizoctonia solani are regularly detected in the roots of pasture plant species(2,3). Up-to-date research is now needed to understand the distribution and abundance of causative agents of disease in modern pasture systems. Ongoing advances in molecular biology allow us to further our understanding of this area.

My PhD project will identify and understand the distribution of fungal soil-borne pathogens in pasture soils of northern AoNZ. Putative pathogenic fungi have been isolated and are being screened using in-vitro and in planta pathogenicity tests. I will develop molecular diagnostics (qPCR/ddPCR) to screen historical soil samples for confirmed pathogenic isolates. Additionally, I will search available soil microbiome datasets for the presence and abundance of these pathogens. Combined, this information can be used to develop cultural, biological, and chemical methods to mitigate against the impact of soil-borne disease in pastures, helping to improve their persistence in modern farming systems under a changing climate.

1. Beukes et al., (2021). Resilient Pastures: Grassland Research and Practice Series. 17:297-306.

2. Dignam et al., (2022). Journal of Sustainable Agriculture and Environment. 1:16-29.

3. Wakelin et al., (2016). Australasian Plant Pathology. 45:289-296.