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History of Accession Deposits

The figure below shows the change in cumulative number of living accessions in INVAM from two years after it was transferred to West Virginia University through 2013. The greatest number of deposits occurred during the first six years with the merger of a local West Virginia collection and the one from Florida as well as deposits from CIAT and other individuals seeking to have a storage location for their stocks. From 1996 onward, new accessions have been deposited at a relatively constant rate, consisting of an eclectic mix of inoculum types: (i) spores mailed in folded filter paper, (ii) “whole” inocula of single species, (iii) “whole” inocula of species mixtures, (iv) trap pot cultures (one or more generations removed from field soil), and (v) on rare occasion, mycorrhizal roots. The plateau, and even slight decline at times, in total number of accessions is the result of many deposits consisting of trap cultures from exotic areas (saltwater wetlands, tropical sites with high organic matter, and desert sites with naturally low inoculum potentials), and monospecific cultures that failed to establish or were unable to persist for more than 2-3 generations in our greenhouse environment. It is rare that we receive cultures with verified purity.

Deaccessioning of established cultures (propagated more than four generations) has been very low, accounting cumulatively for less than 8% of accessions deposited over the life span of the collection. When losses occurred, causes varied but the most common was susceptibility to microbial decay or degradation during prolonged storage (often larger-spored species). The most susceptible genus has been Gigaspora, partly because the spores germinate through the spore wall and the germ tube channel often is susceptible to parasite ingress. Near the end of 2013, cultures that were barely growing, were never requested, and were from geographic locations represented by other more sustainable strains were deaccessioned to open up storage space.

graph showing how many acessions each year