Natural Variation Among Monokaryons of Collybia velutipes

The rates of growth of samples of monokaryotic mycelia from the asexual (oidial) and sexual (basidiospore) progenies of seven wild dikaryons of Collybia velutipes were determined. Analyses of the growth-rates of the asexual progenies revealed the presence of variation within a set of mycelia with the same mating-type and hence presumably derived from the same monokaryotic clone. Furthermore, it was possible to select for high and low rate of growth within one monokaryotic clone. This variation is therefore probably cytoplasmic in origin. Analyses of the growth-rates of the sexual progenies showed considerable segregation. The segregation patterns and estimates of the numbers of effective factors suggest a polygenic control. In the case of two of the wild dikaryotic isolates, the segregation of single genes having large effects upon growth-rate was also demonstrated.