Urediniospores of Puccinia sorghi: Pre- and post-cold storage requirements

_{The specific pre- and post-cold storage treatments needed to maintain the viability of urediniospores of rust fungi during storage are species dependent. Urediniospore collections are critical to assess pathogen evolution over time, but most importantly, to determine the efficacy of resistance genes in host plants. Puccinia sorghi, the causal agent of common rust of maize, can cause yield losses of up to 40% in susceptible varieties. The purpose of this study was to optimize the pre- and post-cold storage requirements of P. sorghi urediniospores. Here, we report that dried urediniospores had an 87% decrease in germination compared with undried spores. Urediniospores of P. sorghi were successfully stored at −80°C for 24 months and remained infectious, and did not require cold shock in liquid nitrogen pre-cold storage, nor a heat shock to revive them from dormancy. Urediniospores removed from storage in a freezer at −80°C germinated readily between 22°C and 55°C.}