Biological control of Rhizoctonia root rot on wheat in the field

Rhizoctonia root rot (RRR) caused by Rhizoctonia solani AG8 is a major root disease of cereals and other crops in dryland farming systems resulting in stunting of seedlings and reduced ability to access water and nutrients (1). RRR is difficult to control due to its wide host range and lack of resistant cultivars. New seed applied and in-furrow chemical treatments have recently been registered in Australia for RRR control on cereals and provide partial control (2).
RRR is known to be influenced by soil microbes and a program screening 2,310 microbes using an in planta pathosystem identified 43 strains with the ability to control RRR when applied to seeds (3). Further characterisation for survival on seed and storage, genetic stability, growth, fungicide compatibility, etc., identified 24 strains that appeared suitable for further development as seed inoculants. These strains were assessed in the field in a two-step process: firstly in 1 m replicated micro-plots to assess early season disease control on roots and then in larger 20m plots to assess disease control and yield.