Genetics of Collybia velutipes, VI:Linkage study with a spontaneous physiological mutant
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概要
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The linkage among genes controlling growth, colouration and mating system, was studied. The mating system of Collybia velutipes is dependent on two pairs of incompatibility factors, A and B. In the present study, the independent inheritance of these factors was confirmed (Table 2).The author has obtained a spontaneous mutant monokaryon by isolating single basidiospores derived from the fruit-body NL-55P. A wild-type monokaryon grows rapidly with abundant aerial mycelium and is yellow or yellowish-white; whereas the mutant is slow-growing with scant aerial mycelium and is pure white without any trace of colour (Fig. 1). The combination, wild-type haplont×mutant monokaryon, yielded a dikaryotic hybrid mycelium which grew more rapidly with abundant aerial mycelium than the wild-type parent and was coloured (Fig. 1 and Takemaru, 1957a). It is clear that, in the hybrid dikaryon, fast growth, colouring, and luxuriant aerial mycelium of wild-type monokaryon are dominant over slow growth (fa), colourless (c), and reduced aerial mycelium (ae) of mutant monokaryon, respectively.As shown in Table 3, each of these mutant genes, c, fa, and ae, segregates in 1:1 ratio with respective wild-type genes. Table 4 indicates that no linkage exists between the mutant genes and incompatibility factors.The three mutant genes belong to the same linkage group, being arranged in order of c-fa-ae. The map distance between c and fa is 75/328=22.9 units, and that between fa and ae 46/328=14.0 units. Coefficient of coincidence is 0.76 (Table 5).Wakayama (1932) has reported that the haploid number of chromosomes for C. velutipes is four, suggesting the existence of four linkage groups in the fungus. In the present study, three of the four linkage groups were detected (Fig. 2).
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