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Effect of sodium azide and N-nitroso-N-methylurea
on M1 and M2 generations of hexaploid Triticale (x Triticosecale)1)
V.T. SAPRA, J.L. HUGHES and G.C. SHARMA Alabama A and M University, Normal, Alabama, U.S.A. In recent years chemical mutagens have been used extensively in cereal grains to create genetic variability for desirable traits and as a source of new germ plasm material (BROCK 1971, KONZAK 1973). Genetic variability has been shown to increase considerably with increasing concentrations of mutagens (VAGERA 1969 and 1971; KONZAK et al. 1964). The limited variability in existing triticales offers an excellent opportunity to generate new genotypes in a relatively short time by mutation breeding. To date, only very few studies have been reported on the use of chemical mutagens in this new cereal crop. The objective of this study was to examine the effect of varying concentrations of sodium azide (NaN3) and N-nitroso-N-methylurea (MNH) on seedling establihsment and other plant characteristics of hexaploid triticale in the M1 and M2 generations. Materials and Methods Seeds of hexaploid triticale cultivar 6TA 131 were presoaked in water for two hours at 30C. The mutagen solutions were freshly prepared in 0.05M phosphate buffer at pH 3.0 for NaN3 and at pH 7.0 for MNH. Seeds were soaked in three concentrations of NaN3 (1.0, 1.5, 2.0 g/l) and MNH (0.20mM. 0.25mM, 0.30mM) for 4 hours at 30C. After treatment, they were rinsed in distilled water for two hours and air dried for three days (procedure suggested by C.F. KONZAK, Personal Communication). One hundred seeds were space-planted in a four-meter single-row-plot with four replications in a randomized complete block design for both M1 and M2 generations in October of 1972 and 1973, respectively. Seedling establishment was recorded four weeks after each planting date. Plant height, length of first internode below peduncle, length of spike, seed set and 1000 kernel weight were determined on ten randomly-selected plants per plot in both M1 and M2 generations. Results and Discussion In the M1 generation, increases in concentration of sodium azide reduced the seedling establishment from 60% in control to below 20%, but no differences due to treatments were found in the M2 generation. Concentrations of MNH did not affect stand establishment in either generation (Fig. 1). VAGERA (1969) reported strong depression of germination at similar concentrations, particularly at 0.3mM concentration of MNH in einkorn wheat seeds. Sodium azide treatments caused about 35cm reduction of plant height in M1 generation when compared with the control but no significant differences were observed between concentrations (Fig. 1). However, M2 plants were as tall as the control, indicating that the height depression in M1 plants was probably a reduced vigor caused by mutagen treatment instead of being a genetically expressed change observed in later generations. Mean plant height was not affected by MNH treatment in either M1 or M2 generation. |
| 1) The work reported is upported by the U.S. Department of Agriculture, Cooperative State Research Service Grant Nos. CSRS 416-15-07 and CSRS 316-15-27. |
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