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Fractal geometry of diffuse mycelia and rhizomorphs of Armillaria species

1995; Cambridge University Press; Volume: 99; Issue: 1 Linguagem: Inglês

10.1016/s0953-7562(09)80320-1

1469-8102

J. D. Mihail, Martin Obert, Johann N. Bruhn, S. J. Taylor,

Plant and animal studies

Fractal geometry was used to quantify the variation in branching patterns of sibling basidiospore-derived diffuse mycelia of Armillaria gallica and rhizomorph systems of A. gallica and A. ostoyae in laboratory culture. The fractal dimension (D) of 11 A. gallica diffuse mycelia ranged from 1·05 to 1·20 at 74 h after basidiospore germination, and from 1·43 to 1·57 at 116 h after germination. The coefficient of variation (CV) for the regression coefficients of D on time was 14·8%, whereas the CV for D of all 11 mycelia at the fourth measured time step was only 2·9%, indicating significant convergence towards a given branching pattern for a particular set of environmental conditions. The rhizomorph systems of diploid A. gallica thalli branched more profusely than those of diploid A. ostoyae. D values among replicate rhizomorph systems for strains representing three A. gallica genets were similar, whereas rhizomorph systems of eight of the 12 A. ostoyae thalli, also representing three genets, either failed to develop or did not branch sufficiently to permit calculation of D. D values of rhizomorph systems were generally temporally invariate for both species. The CV of D for replicate rhizomorph systems at the fourth measured time step was between 1·6% and 3·9% for A. gallica genets and 2·4% for the A. ostoyae genet; D was significantly lower for the A. ostoyae genet than for the three A. gallica genets. A. gallica is only weakly pathogenic and can colonize a taxonomically broad range of food bases saprotrophically. A. ostoyae is more pathogenic and colonizes a narrower range of substrata. The profuse rhizomorph branching pattern of A. gallica is consistent with a foraging strategy in which acceptable food bases may be encountered at any distance, and which favours broad and divisive distribution of potential inoculum. The sparse branching pattern of A. ostoyae rhizomorph systems is less divisive, consistent with the conservation of nutrients necessary to maintain rhizomorph inoculum potential more efficiently with increasing distance from a foodbase.