Lynne Boddy

Effect of temperature and water potential on growth rate of wood-rotting basidiomycetes

Radial growth of twelve species of wood-rotting basidiomycetes was examined over a range of temperatures on malt agar: optimum growth rate occurred at between 20 and 30 °C. Variability in growth rate of several different isolates of five of the species was assessed at 10° and 20°. A significant difference in growth rates of different isolates was found in four species at 20° but only in one species at 10°. No significant difference was detected between the Q10 coefficients of different isolates of a species. The effect of water potential on growth rate was investigated for one isolate of each of the twelve species using four different solute systems and two types of agar media. Differences were detected between the solute systems and media although a general trend of decrease in growth rate with decrease in water potential was observed. The limit for growth was about −4.4 MPa (− 45 bars).

Mycelial interactions, morphogenesis and ecology of Phlebia radiata and P. rufa from oak

Attached or fallen branches of oak ( Quercus robur ) colonized by Phlebia radiata and P. rufa were collected from locations in South-West Britain, and the patterns of decay within the branches analysed. Isolates were cultured from decayed wood, fruit-body tissue and from single basidiospores. Isolates were paired on malt agar in various combinations and also against other species of decay fungi. Bipolar incompatibility was found in both species, although P. rufa behaved inconsistently, and intraspecific pairings between genetically different dikaryons were mutually antagonistic. Pairings between the two species always resulted in strong mutual antagonism, immediately after hyphal fusion, and no dikaryons with clamp connexions were formed between homokaryons. Both species tended to replace other decay fungi in culture, but P. radiata was generally the more successful. All of the above interactions appeared to depend on contact with septate mycelia. Colonies of both species on agar extended relatively rapidly from a wide peripheral zone of appresed, mostly coenocytic mycelium which generally lacked hyphal fusions. Behind this zone, which was wider in P. radiata than in P. rufa , hyphae with clamp connexions developed and aerial mycelium was formed. The aerial mycelium of P. rufa was generally rather localized and rapidly aggregated into small hymenial surfaces on homokaryotic and dikaryotic mycelia. P. radiata formed a much more diffuse, floccose aerial mycelium which formed hymenia only occasionally on old cultures. Homokaryotic and dikaryotic cultures of both species produced oidia, although P. rufa did so more abundantly and more consistently than P. radiata . The cultural differences between the two species were correlated with differences in their ecology: P. radiata is regarded as a secondary colonizer, but P. rufa is probably a pioneer colonizing weakened, but still-living wood.

Population structure, inter-mycelial interactions and infection biology of Stereum gausapatum

Isolates from wood, fruit body tissue and single basidiospores of Stereum gausapatum from several locations in South-West England showed several types of reaction when paired on 2% malt agar. ‘Compatible’ reactions resulted in the formation of a distinct secondary mycelium between monospore isolates. ‘Lytic’ reactions resulted in the development, between monospore isolates, of a crescent-shaped zone of appressed mycelium bounded by regions of liquid droplet exudation. In pairings between sibs, the distribution of these two reaction types showed a reciprocal relationship depending on which fruit body had been used for isolation. In non-sib pairings the compatible reaction predominated although, as in a few sib pairings, in many instances it appeared to follow an initial lytic reaction. A narrow pigmented zone of ‘mutual antagonism’ was usually formed between different wood or fruit body tissue isolates, or laboratory-produced secondary mycelia, and also between certain non-compatible/non-lytic combinations of monospore sibs. Some interactions between monospore sibs were ‘weak’, with little or no pigment production or other obvious effect. These observations suggest that S. gausapatum is heterothallic and that there is a link between the mechanisms underlying the lytic and compatible reactions. The implications in the infection biology of S. gausapatum and in relation to findings for other Stereum spp. are discussed.

Fungi inhabiting oak twigs before and at fall

Isolations of fungi were made from various categories of attached and fallen twigs of oak (Quercus robur). A similar range of species was isolated from non-living twigs of all types, the most characteristic being Tubakia dryina, Colpoma quercinum and Cryptosporiopsis quercina, but twigs abscissed at leaf fall were much more extensively colonized than those abscissed at other times of year. Basidiomycetes were obtained on several occasions from all categories of fallen twigs, but not from living attached twigs. Colpoma quercinum frequently produced numerous, somatically incompatible mycelia, separated by dark interaction zone lines in non-living twigs, both before and after abscission.

INTERNAL SPREAD OF FUNGI INOCULATED

The white-rotting basidiomycetes Exidia glandulosa, Peniophora quercina, Phellinus ferreus, Schizopora paradoxa, Stereum gausapatum and Vuilleminia comedenswere inoculated into attached living branches of oak (Quercus robur). Patterns of establishment and spread varied in relation to species, time of inoculation and location with respect to branch order and proximity of experimental girdles. Peniophora quercina, Stereum gausapatum and V. comedens readily formed localized decay columns within 6 months, but apparently failed to extend further subsequently. The other fungi either failed to establish, or spread only for limited distances, E. glandulosa preferentially colonizing bark. Longitudinal spread was often markedly facilitated within the vicinity of a girdle, although radial and tangential spread were restricted. In several instances, individuals of Peniophora quercina, Stereum gausapatum and V. comedens became established naturally within the branches. Such individuals were invariably somatically incompatible with those inoculated, and further contrasted with the latter in giving rise to columns of considerable longitudinal and radial extent.

Attraction of fungus gnats to zones of intraspecific antagonism on agar plates

The specific attraction of Mycetophilid fungus gnats to zones of intraspecific antagonism, between somatically incompatible colonies of wood-decaying Basidiomycotina and Ascomycotina, is described and discussed.