Dr. McPartland is an expert on Cannabis [marijuana and hemp] diseases, including Fusarium
oxysporum.  His is the primary author of a forthcoming book to be published by Oxford University Press called Hemp Diseases and Pests:  Management with an Emphasis on Biological Control.


"Below is cut-and-paste from my Botany Department seminar, the part of the lecture that concerned FoxyC mutability.  Feel free to use the material ..."

Fusarium wilt slide (slides coming later): The fungus causing this wilt disease is Fusarium
oxysporum.  We decided it made a poor candidate as a mycoherbicide, for several reasons:  the fungus is probably not host-specific to Cannabis, it grows well at human body temperature, and it produces mycotoxins. Furthermore, it is a soil organism, a facultative parasite, so it can survive in soil saprophytically for up to 40 years, waiting for a host.
Persistence in the environment is not a good thing, as we know from DDT. Persistence in a biocontrol gives it the opportunity to mutate and switch hosts.

Fusarium genetic variation slide (slides coming later): Fusarium oxysporum can mutate easily
because 5 percent of its genome consists of transposons.  Transposons are chunks of DNA which spontaneously move from one chromosome to another. Transposons generate chromosome polymorphism, via reciprocal translocations, inversions, and deletions.  Fusarium oxysporum contains more known transposons than any other fungal species. Thus far, eight families of transponsons have been found  Foret1, Fot1, Fot2, palm, impala, Hop, Skippy, Joyrider.

Anastamosis slide (slides coming later): Mutations arising in Fusarium oxysporum can be
transmitted horizontally, to neighboring fungi. This microphotograph illustrates anastamosis, between two strains of Fusarium oxysporum.  When the fungi fuse their cells together, transposons can spread from one fungus to another.

Now, lets add genetic engineering to this scenario. In 1998 the US Congress appropriated $23 million dollars to develop mycoherbicides against drug plants, and unfortunately, they chose this species, Fusarium oxysporum.  Congress also approved the use of genetic engineering to
enhance virulence.  Fusarium oxysporum has already been genetically engineered to express antibiotic resistance. The resistance gene came from a bacterium.  Suppose the bacterial gene was engineered into a transposon. Five percent chance, right? 

Histoplasma slide (slides coming later): The transgenic Fusarium is capable of anastamosing with
other species of soil fungi.  Suppose it fused with Histoplasma capsulatum. The Fusarium could transmit its transposon to this humanpathogen, which then mutates into a virulent, transgenic horror.