Truffles via Agrobacterium rhizogenes - of course!

I have been musing on how one would go about getting truffle fruiting bodies to form on agar plates, in vitro, and came across a section in Ian Hall's latest book (Taming the Truffle: the history, lore, and science of the ultimate mushroom, co-authored with Gordon Brown and Alessandra Zambonelli) which describes a technique for doing just this.

It would be fair to say I've had a wee obsession with truffles ever since I read The Black Truffle (also by Ian Hall) in my university years. Truffle oils are definitely more in my budget than the real thing, so I can only imagine what they might taste like.  But as to growing them myself - then the whole delightful venture takes on an appearance mid-way between science and magic! The first truffiere set up in New Zealand was in my home town Gisborne, and produced truffles within 5 years of planting. This is really fast - many more truffieres have been planted around the country which are still waiting on their first treasure.

Growing truffles on agar plates is quite possibly a holy grail - ingeniously dispensing of the need to inoculate roots of living trees with the fungus, and all of the orchard set-up and ongoing management.  Instead, infected root is produced using transformed roots which are able to grow without an attached shoot. This kind of system has also been used for arbuscular mycorrhizal fungi, and is described by Varda Kagan-Zur (2006) and colleagues. Derooted rockrose (Cistus incanus) seedlings are inoculated with Agrobacterium rhizogenes, a bacterium that carries the Ri (root-inducing) plasmid which induces root galls on some trees. The roots then produce thin, delicate hairy roots 8-11 days after inoculation, and can be transferred individually to liquid culture medium containing antibiotics.

The inoculated roots are then grown on a solid culture medium containing lower concentrations of antibiotics and nitrates, and transferred to solid media capable of supporting the endomycorrhizal association.   A piece of agar containing actively growing perigord black truffle hyphae is placed in the middle of a bunch of hairy roots growing on solid medium and voila! after 3 months, mycorrhizae forms in the elongated roots, and about 2 months later, short, club-like root forms can be observed. These are then further encouraged to produce truffles, probably even in a commercial way.

Heck of a lot easier than asking a sow to give it up once she's sniffed one out too!!