Martin J. Barbetti

1 Introduction Rapeseed (canola, Brassica napus) is the second-largest oilseed crop worldwide after soybeans (STATISTA 2025). Australia alone produced 6.8 million tonnes in 2022, including 3 million tonnes from Western Australia (Australian Bureau of Statistics 2023). Weeds are a significant global threat to crop yields and quality; for example, in Australia and the United States of America, annual expenditure on weed management surpasses $US30 billion (Abouziena and Haggag 2016).

1 Introduction Legumes (family Fabaceae) play an important role in global food security, crop diversification and ecosystem sustainability (Stagnari et al. 2017). They also provide many other ecosystem services like atmospheric nitrogen (N) fixation and allow colonisation of arbuscular mycorrhizal fungi, which boost nutrient uptake and water supply in host plants (Ditzler et al. 2021).

Abstract Root diseases are a major global threat to sustainable agricultural production. Complexes of interacting soilborne fungal, oomycete and nematode pathogens are involved in causing these diseases that are generally termed root disease complexes. These soilborne pathogen complexes typically have resilient long-term survival mechanisms, the ability to cross-infect multiple crop genera and species, and a wide range of spatial dispersal modes.