untitled

spore germination, and also containing a dye

(bromocresol purple). For application to stump surfaces,

the sachets were diluted with water, allowing the

spores to germinate, and the dye enabled foresters

to see that the stump surfaces had been treated.

More recently, the spores have been produced as dry

powder formulations by commercial companies.

This biocontrol system proved highly effective in pine

forests over much of Europe and North America. But

in Britain it had one significant limitation – P. gigantea

could be used only to protect pine stumpsand was

not effective in protecting Sitka spruce, which is the

most common plantation tree in Britain. Now it seems

that there is a simple explanation for this: the strains

of P. giganteaused to control the disease in Britain are

endemic strains, specialized to colonize pine stumps,

whereas the strains used in Scandinavia have a broader

host range and can protect spruce as well as pines.

In Finland a commercial preparation of P. gigantea,

marketed as Rotstop™, effectively controls H. annosum

on spruce. The UK Forestry Commission is currently

investigating the possibility of introducing such strains

into Britain.

Mycoparasites: fungi that parasitize other

fungi

The fungi that parasitize other fungi can be grouped

into two broad categories: necrotrophic mycoparasites,

which invade and destroy other fungal cells and then

feed on the dead cell contents, and biotrophic myco-

parasites, which can establish a specialized feeding

relationship, usually by producing haustoria to pene-

trate and absorb nutrients from living fungal hyphae.

These two types of mycoparasite are equivalent to the

necrotrophic and biotrophic parasites of plants, dis-

cussed in Chapter 14.

Biotrophic mycoparasites

There are several types of biotrophic mycoparasite

with different feeding mechanisms ( Jeffries & Young

1994), but the most common and distinctive group are

the haustorial biotrophs. These fungi penetrate living

host hyphae to produce a haustorium inside the host

wall but separated from the cell contents by a host cell

244 CHAPTER 12

Fig. 12.9Possible mode of action of Phlebiopsis giganteain controlling Heterobasidion annosumin recently felled pine
stumps. 1, P. giganteais inoculated onto freshly exposed stump surfaces and prevents colonization of the stumps from
airborne basidiospores of H. annosum(shown by the double lines). 2, When P. giganteahas colonized the dying stump
and root tissues it prevents the spread of H. annosumfrom existing foci of infection in the root zone. 3, P. gigantea
might also prevent H. annosumfrom growing up to the stump surface to sporulate.