Imbalanced nuclear ratios, post-germination mortality and phenotype—genotype relationships in allopatrically-derived heterokaryons of Heterobasidion annosum
Article first published online: 28 APR 2006
Volume 133, Issue 2, pages 303–319, June 1996
How to Cite
RAMSDALE, M. and RAYNER, A. D. M. (1996), Imbalanced nuclear ratios, post-germination mortality and phenotype—genotype relationships in allopatrically-derived heterokaryons of Heterobasidion annosum. New Phytologist, 133: 303–319. doi: 10.1111/j.1469-8137.1996.tb01898.x
- Issue published online: 28 APR 2006
- Article first published online: 28 APR 2006
- (Received 23 February 1995; accepted 19 October 1995)
- Episodic selection;
- genomic conflict;
- non-self recognition;
- nuclear–cytoplasmic relationships;
Twelve heterokaryotic strains of Heterobasidion annosum (Fr.) Bref. containing nuclei and mitochondria derived from British and North European populations were prepared by pairing homokaryotic strains and isolating hyphal tips from either side of interaction interfaces. Conidia derived from the heterokaryons had high germinability and were predominantly uninucleate. The nuclear genotypes recovered from these conidia were predominantly nonresident in origin, reflecting the marked asymmetry m nuclear ratios (as high as 9:1) in favour of invasive nuclei that developed in the mycelium. In spite of this asymmetry, the heterokaryons had similar phenotypes to the resident homokaryons that they were derived from.
Whereas the relative ability of sib-related nuclei to become established in a homokaryon was about equal in sympatric protoplasm, it could be very different in allopatric protoplasm. Post-germination mortality due to the cessation of development following transfer of germlings to fresh medium was on average similar for allopatric and sympatric conidia, but there was a marked trend for reduction in mortality as nuclear ratio asymmetry increased. Homokaryons derived via conidia from a common heterokaryon exhibited less somatic incompatibility when paired together than did the original, basidiospore-derived strains.
These findings indicate that phenotype–genotype relationships resulting from allopatric matings, such as could occur following geographical transposition, are liable to differ radically from those in sympatric matings and so have potentially profound effects on resident population structure.