Long-Term Survival of Glomus claroideum Propagules from Soil Pot Cultures under Simulated Conditions

This study was initiated to determine the effect of storage conditions on Glomus claroideum. Pure cultures of this AM fungus containing approximately 80 spores/g were stored in Dothan soil under four temperature-moisture regimens: room temperature 24 C at field capacity (FC) and at 50% FC and refrigeration (4 C) at FC and at 50% FC. Soil samples were taken at 0, 2, and 4 wk, monthly thereafter until 48 wk, and then at 72, 104, 156 and 272 wk and assessed for spore numbers by sucrose gradient centrifugation. Spore viability was also assessed by most probable number and by vital staining with 2-(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyl-2H-tetrazolium chloride (INT). Spore losses were less when cultures were stored at 4 C than at 24 C. The half-life of G. claroideum spores was approximately 2 yr at 24 C and 3.5 yr at 4 C. Spore numbers of G. claroideum stored for 272 wk at 24 C and both moisture levels decreased from 80 to 12 spores/g while those stored at 4 C decreased to approximately 30 spores/g. Most probable numbers of total G. claroideum propagules stored at 4 C were significantly higher than cultures stored at 24 C. Temperature was more critical than soil moisture for survival. Even after 272 wk at 4 C, there were sufficient viable propagules of G. claroideum (300/g) to be used as an inoculum for studies with AM fungi. Viability staining demonstrated that the percentage of viable spores decreased with time of storage. These results demonstrate that the best method of AM fungi culture storage in Dothan soil is at 4 C and moisture conditions less than or equal to field capacity.