Aiming to screen mutant genes on nine chromosomes of homoeologous groups, I, V and VII in common wheat (Triticum aestivum L.), selfed seeds of their monosomics and a normal disomic line of cv. Chinese Spring were treated with 0.3 and 0.4% ethyl methanesulphonate(EMS). Higher survival was observed in mono-1A, 1B and 1D than in other monosomics and the normal line in the M
1 generation, indicating some increase of tolerance to EMS by the hemizygous state of either the 1A, 1B, or 1D chromosome. A few M
2 Iines were bred true for weak chlorosis and necrosis(mono-1A, 1B, 1D, 5A, 5B, 7A, 7D), seedling lethality (mon0-1B, 1D), striped leaf color (mono-1B), dwarfing (mono-1A, 1B, 1D, 5D), or for compactoid (mono-5A) and sphaerococcoid characters (mono-7B, 7D). According to the scheme shown in Fig.1, most of these mutations were assumed to have occurred on a chromosome that was monosomic in the M
1 generation. Unique consequences of the mutagen treatment of monosomics, compared to that of disomics, in the M
1 and M
2 generations are pointed out.
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