Using microwave radiation to destroy macroconidia of the cereal pathogen Fusarium pseudograminearum: a hot solution?

Abstract

Cereal production in Australia is impacted by stubble-borne diseases such as crown rot, caused by the fungus Fusarium pseudograminearum (Fp). The disease can be difficult to manage, as Fp can survive within crop residues as macroconidia or mycelium across multiple seasons. Microwave radiation may offer a rapid and chemical-free approach to destroying Fp inoculum within stubble. The energy required to kill Fp macroconidia using microwave radiation was therefore investigated in a microwave dose response experiment. Suspensions of macroconidia of Fp (2.6 x 104 macroconidia/mL) were microwaved in a conventional 1100 W microwave oven for 0, 4, 5, 6, 7, 8, 9 and 10 seconds. Viability after microwaving was assessed by counting colony forming units (CFU) following dilution plating on ¼ potato dextrose agar plus novobiocin. Conidial viability declined as the energy applied increased. Significant reductions in viability (>90% reduction in CFU) were achieved after 7 seconds of microwave treatment, or 131 Jg-1 of energy. Macroconidia were completely non-viable following microwave treatment times of 8 seconds or longer. The minimum mean energy and temperature requirements to achieve total death were therefore 172 Jg-1 of energy and 62.5˚C, respectively. Thus, microwave radiation can be used to destroy Fp macroconidia using a relatively small energy dosage. This method could be used for assessing the susceptibility of other plant pathogens to microwave radiation, and potentially adapted for treating inoculum in soil and stubble for crown rot management under field conditions.