High temperature during storage favours infection potential of resting spores of Polymyxa graminis of Indian origin

The infection potential of sporosori of Polymyxa graminis involved in the transmission of the Indian peanut clump virus (IPCV) was assessed by culturing bait plants exposed to various concentrations of sporosorus suspensions and then determination of the numbers of plants that became infected. Storage of air-dried inoculum at temperatures above 30°C resulted in an increase in the infection potential compared to that of sporosori stored at 15°C or 20°C. In contrast, when the sporosori were stored at -20°C or freeze-dried, their infection potential was low. These results confirm the adaptation of P. graminis isolates associated with IPCV transmission to the tropical environment. The implication of storage temperature for the epidemiology of Indian peanut clump virus and for the assessment of the infection potential of the vector in the soil is discussed.