MORPHOLOGICAL-CHARACTERISTICS OF INCOMPATIBILITY REACTIONS AND EVIDENCE FOR NUCLEAR MIGRATION IN ARMILLARIA-MELLEA

A new technique was developed to distinguish the four incompatibility interactions in Armillaria mellea sensu stricto. The technique involves confronting two single-basidiospore isolates on oak wood extract agar and then transplanting a strip from the colonies including the interaction zone onto squeezed orange juice agar. A compatible (A not-equal B not-equal) interaction results in a change of the colony morphology along the entire agar strip. Morphological characteristics of compatible interactions are highly variable. They may be expressed as appressed or crustose secondary mycelium. In a common B (A not-equal B=) interaction, such a change occurs only in the interaction zone. The ends of the agar strip remain white and fluffy. Both the common A (A=B not-equal) and common AB (A=B=) interactions remain fluffy and unchanged. The genotype can be deduced after identifying the A not-equal B not-equal and A not-equal B= interactions. In addition. pairing mycelium produced by the confrontations with known monosporous tester isolates showed that nuclear migration occurs in A=B not-equal and A not-equal B not-equal interactions but does not occur in A not-equal B= interactions.