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Scutellospora heterogama -- preparing clean healthy spores for shipment
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Extracted population of spores. Fungal species with darkly pigmented and ornamented spores are amongst the most difficult to remove unwanted spores from an extracted population. The main reason is that there is not dramatic contrast between healthy spores and those in various stages of degradation or parasitism. Among large-spored species, Scutellospora heterogama is an excellent example of what can be expected. In the photo at left, almost 30% of the spores exhibit some departure from the typical healthy spore and must be removed, but the phenotypes don't just "pop out" with casual observation under a stereomicroscope. Part of the problem is that the surface spines covering the spore wall attract a coating of organic material that appears white under reflected light and this is ubiquitous for most spores. Therefore, the culling process requires diligent perusal under higher magnifications. | |
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| The problem with roots. Once spores are extracted, they should be immediately separated from any root fragments carried along in the sieving process. Otherwise, with less than 12 hr incubation, hyphae often begin to grow from root fragments and bind spores with debris. This is especially true for culture material that has been stored for 6 months or longer. In the photo above are aggregates from a combination of fungal saprophtes' hyphae and that of S. heterogama. | Spores with irregular contents. For darkly pigmented spores where discoloration is not as readily apparent, we rely on signs of disruption in cellular contents. Spores with any compartmentalization of lipids, patchiness, milky appearance, etc. (a range of phenotypes are exemplified in the photo above) are deemed unhealthy and removed. When otherwise healthy-appearing spores undergo changes to any of these phenotypes over 48 hr incubation, they also are removed. | Parasitized spores. The most common parasites of spores are saprophytic fungi and some actinomycetes. In addition to changes in spore contents (at left), signs of hyphae emanating from parasitized spores become apparent after 24-48 hr of incubation at 4oC. If hyphal growth is not immediately noticed and aggregates of spores develop, then ALL spores in these clumps should be removed. |
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Healthy
spores that have shown little change over at least 24 hr are considered
ready for shipment in sterile sand. Again, it is important to note that
with ornamented spores, such as those of S. heterogama, a uniform
coating of material on the external surface of spores is normal (see spores
at left). Notice that the spores in this photo have relatively uniform
lipid globules. Any deviation from this, even if spores otherwise appear
healthy, warrants removal. With darkly pigmented spores, it is better
to err on the side of caution. |
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