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Plant Health Week – day 3

Having written about two very large and very important plant diseases, I want today to focus on a much less known fungal pathogen, Rhizoctonia solani.

Department of Plant Sciences

There is a personal aspect to it. In 1993 I joined the Department of Plant Sciences at the University of Cambridge as a post-doctoral researcher. I already had been working on human disease modelling, but this was the first time I encountered plant pathogens. Colleagues who were biologists and mycologists introduced me to a wonderful world of soil-borne fungi. I have been fascinated with the fungi ever since.

Rhizoctonia solani damping off on radish seedlings.

Rhizoctonia is a group of fungi causing various symptoms in plants, including sheath blight (the second-most devastating disease of rice after rice blast) and damping-off which affects seedlings. In the field, it can form densely infected patches causing large yield losses.

Rhizoctonia experiments

As a modeller, I was not allowed to do experiments (in case I do something stupid which will spoil the work), but I enjoyed seeing the experiments set up. We grew Rhizoctonia solani in trays filled with sand in which seedlings of brassicas (radish, cauliflower) were planted.

Rhizoctonia experiments

Another fungus, Trichoderma viride was introduced on poppy seeds, in an attempt to control the disease. A poppy seed had to be placed in an exact position and if dropped by mistake, they would ruin the experiment. It was amazing that the poppy seeds could not really be distinguished from grains of sand which made placing them tricky – but Rhizoctonia knew exactly where they were. A race between Rhizoctonia and Trichoderma ensued to see which one will get to “food” earlier.

Field experiments

We also did field experiments and I really enjoyed going out, meeting farmers and getting my boots dirty. Talking to people who actually grow the plants – propagators, farmers and farm managers – made me realise that mathematical and statistical modelling of plant pests and diseases must be connected to economics and behavioural sciences – a line of research that I have been pursuing since.