Bistability and hysteresis of the 'Secteur' differentiation are controlled by a two-gene locus in Nectria haematococca

Table 1 Mutagenesis efficiency and spectrum of mutants

Mutagen^a	Total number of irradiated thalli	Total number of fast-growing sectors	Types of mutants^b
			nas	s*	s
UV₁	12	15	15	-	-
UV₂	26	53	53 (13)	-	-
UV₃	21	40	39 (6)	1 (s*₁₁)	-
UV₄	28	50	49 (16)	1 (s*₂₇)	-
UV₅	44	75	74	1 (s*₄)	-
UV₆	21	17	17	-	-
NG₁	28	25	22	2	1(s₁)
NG₂	22	38	37	1 (s*₁₈)	-
NG₃	26	42	37	5	-
Total	228	354	343	11	1
		1.5 per dish	97	3

^aUV, 254 nm UV irradiation; NG, N-methyl-N'-nitro-N-nitrosoguanidine. ^b nas mutants differentiate neither Anneaux nor Secteurs at 26°C but some may do so at other temperatures. Their number are indicated in brackets; s* mutants differentiate Anneaux but not Secteurs, though they have the σ determinant throughout the mycelium; s, cultures differentiate Anneaux but not Secteurs, and never contain the σ determinant.

ISSN: 1741-7007