Genetic and Environmental Aspects of Fruiting in Schizophyllum Commune Fr.

SUMMARY

An extensive study of fruiting in a large, world-wide sample of Schisophyllum has revealed genetic background as the most critical factor in determining the occurrence and time of fruiting and the form of the fruiting bodies.

In a sample of 116 homokaryotic mycelia cross-mated in all combinations, fruiting occurred in 80% of the resulting 6546 dikaryons. The occurrence and time of fruiting, however, were not random: good fruiting and poor fruiting were conspicuously correlated with specific component strains. Detailed analysis of a smaller sample of 80 strains permitted a quantitative determination of fruiting competence and the classification of individual strains in respect to the character.

Fruiting competence is inherited as a quantitative character; in dikaryotic mycelia, poor fruiting potential is masked by high fruiting competence.

Five fruiting abnormalities, each genetically determined, have been analyzed and may be characterized as follows:

a.	Cauliflower, a severely malformed, gill-less fruiting body; a quantitatively inherited character that is completely suppressed in matings with wild-type strains.
b.	Medusoid, a profuse, irregular outgrowth of cylindrical projections (presumptive stipes?) that may open at their ends to produce small, normal fruits; a quantitatively inherited character that is only partially masked in matings with wild-type strains.
c.	Bug's ear, a reduction of the fruiting body to a small (<1 mm), ear-shaped fold, bearing hymenium on its lower, concave surface; a single-locus, dominant character.
d.	Coralloid, a compact, convoluted, darkened fruiting body, sometimes expressed as a simple, microscopic, cup-shaped structure lined with hymenium (micro-coralloid); a single-locus, dominant character, always associated with a mycelial aberration and the production of indigo; either a pleotropic locus or three extremely closely linked loci; location known as to linkage group.
e.	Haploid (homokaryotic) fruiting, variously expressed in different strains from only slightly stunted, gilled fruits to amorphous knots of compressed hyphae; sporulation sparse, spores mostly non-viable; a quantitatively inherited character distinct from dikaryotic fruiting competence.

The effects of light, nutrient, and other environmental factors have been again confirmed, but no restoration to normal fruiting in genetically inadequate stocks has been achieved through alterations of external factors.