GENETIC-VARIATION IN ANTIFUNGAL ACTIVITY BY SIBLING ISOLATES OF THE ECTOMYCORRHIZAL FUNGUS PISOLITHUS-ARHIZUS

Liquid culture media in which homokaryons of Pisolithus arhizus from Australia and South Africa, and synthesized heterokaryons from South Africa had grown, were assayed for inhibition of the germination of conidia of the seedling pathogen, Truncatella hartigii. Ten homokaryons from an Australian strain displayed a wide-range of variability, with one isolate inhibiting germination completely, and four out of 22 South African homokaryons tested inhibiting germination completely. Only one isolate of the homokaryons from South Africa inhibited germination completely when the culture filtrate was diluted 3:1. A wide range of variability was recorded for 41 synthesized South African heterokaryons; seven of these inhibited conidial germination completely. To determine whether the variability was correlated with mycelial weight accumulation during culture, three different germination inhibition groups were compared, two groups of heterokaryons, one weak and one strong, and one group of wild-type dikaryons. There was no correlation detected between germination inhibition activity and biomass. The variability in antifungal activity suggests the possibility of selecting a cross of P. arhizus effective for root protection.