|Radiation induced mutations in bread wheat (Triticum
aestivum L. em THELL.) var. Hira
YASHVIR, Asha LATA and P. K. GUPTA
Cytogenetics Laboratory, Division of Plant Sciences. Meerut University, Meerut, India
In the last two decades, it has regularly been emphasized that in wheat it would be increasingly difficult to obtain further increase in yield through conventional breeding methods, utilizing existing germplasm. It is also difficult to locate additional natural sources for several useful characters, and if these useful attributes are found in alien species, their incorporation into wheat through cytogenetic techniques is very laborious. Under such circumstances, additional genetic variability will have to be created through induced mutations.
The research work on induced mutagenesis in wheat has received renewed attention due to the success achieved in this crop in recent years. At least eleven wheat varieties, utilizing induced mutations have so far been released (IAEA report 1972). Variability in floral morphology for outbreeding devices will be of some significance in hybrid wheat production, if artificially induced. Keeping these views in mind, radiation induced mutations in wheat var. Hira were studied in some detail in M3 generation and are being reported in this communication.
The seed of wheat var. Hira was obtained from Genetics Division, I.A.R.I., New Delhi, and was irradiated in the winter of 1970-1971 with four different doses of gamma rays (10Kr, 20Kr, 30Kr and 40Kr). The M2 generation was raised as single plant progenies in 1971-1972. The M3 generation was similarly raised, but only from the suspected mutant lines of M2 generation. In M3 generation, 336 lines, which could be traced back to 42 plants of the M1 generation, were analysed. Since whole population derived from M1 plants could not be studied, it was not possible to work out the mutation frequencies and only qualitative study of the different kinds of mutations could be undertaken. The following mutants were recorded.
1. Mutants for plant height:
Considerable variatin in plant height was observed. The plant height varied from 70-90 cms in control. In treated lines, the taller ones ranged from 90-120 cms and the dwarf ones ranged from 35-70 cms. There were other lines which segregated for tallness or dwarfness. The variation in plant height could be due to variation in the number and/or size of internodes.
2. Erect leaf mutants:
The leaves in the control were drooping, while in the treated popullation, 146 lines out of 336 lines analysed, showed erect leaves without any segregation. There were other 50 lines which showed segregation for this character. It may be concluded that several genes must be controlling this character. However, the length and width of erect leaves were reduced. This morophological character is important because such erect leaves would receive maximum light without causing any shade to the leaves situated below. These leaves were sometimes found in combination with mutants for plant height.