| Induced quantitative variation in wheat
R.K. CHOWDHURY Haryana Agricultural University, Regional Research station, Bawal, 123501 (Haryana) India. Experimental modification of genotype was unknown until the work of MULLER (1927) and STADLER (1928). Since then extensive work on artificial production of mutations, through various mutagenic agents, has been carried out in various crop plants. MIKE (1975) has given a list of crop cultivars bred through induced mutagenesis. The induced mutations have also rendered a significant contribution to the present day knowledge of genetic mechanism particularly in understanding the structure and function of genetic material. The primary aim of mutation breeding are to enlarge the mutation frequency and spectrum of mutations, increase the percentage of viable mutations and to gain some degree of control and precision over mutation process, ultimately leading to directed mutagenesis. This paper reports the preliminary results on the effect of gamma rays on different quantitative traits of wheat in M1 and M2 generations. Materials and Method Dry seeds of six well adapted varieties of wheat (Triticum aestivum L.) namely ; C 306, S 308, WH 147, WH 157, K 227 and HD 2009 were irradiated with gamma rays (Cobalt 60 source) using 10, 20, 30 and 40 KR doses. Counted seeds from each dose (100) and control (50) were sown in randomised block design at the research farm of Regional Research Station, Bawal during 1979-80. The M2 generation alongwith their controls were grown in family block design during 1980-81. The data were recorded from normal looking plants for plant height, tillers per plant, ear length, spikelets per ear and grain yield per plant in each dose and control in M1 and M2 generations. Results and Discussion GAUL (1964) described plant breeding as the controlled evolution. By mutations, plants can genetically be improved. However, future importance of mutation breeding depends on whether it succeeds in securing better control of the whole complicated process of "obtaining mutants" starting with mutation induction to selection. It is still a matter of debate whether radiation induced mutations of polygenes occur towards positive or negative direction. GREGORY (1968) emphasized that mutants with very small phenotypic effects occur with high frequency and will have an equal chance of being positive or negative in their phenotypic effect. OKA et al. (1958) found no change in rice for plant height and heading date. ROWLINGS et al. (1958) reported increase in seed weight of soybean after irradiation and no change in plant height and maturity. While GREGORY (1961) noticed that the yield of dry peanut pods decreased by irradiation. BROCK (1971) emphasized that the induced mutations are expected to increase the variance and shift the mean away from the direction of previous cycle. |
| --> Next |