ABSTRACT
The present study was undertaken to assess the effectiveness and efficiency of gamma rays, EMS and their combined treatments in chickpea. Seeds of two varieties of chickpea (Cicer arietinum L.) were treated with gamma rays (150 Gy, 200G y, 300G y and 400G y), EMS (0.1, 0.2, 0.3 and 0.4%) and their combinations (200 Gy+0.2% EMS, 300 Gy+0.2% EMS, 200 Gy+0.3% EMS and 300 Gy+0.3% EMS). The biological damage was calculated in M1 generation based on seed lethality (L), seedling injury (I), pollen sterility (S) and meiotic aberrations (M). The M2 population was carefully screened for various chlorophyll mutations. Mutagenic effectiveness and efficiency was calculated based on biological damage in M1 and chlorophyll mutations in M2. Mutagenic effectiveness increased with the increase in dose/treatment. Combination treatments in general proved to be more effective followed by individual treatments of EMS and gamma rays. Mutagenic efficiency varied depending upon the criteria selected for its estimation and the degree of efficiency of various mutagens also showed variation. Intermediate treatments in general were found more efficient in causing less biological damage and inducing maximum amount of mutations. The order of efficiency, however, was gamma rays+EMS>EMS>gamma rays. Among the two varieties, var. Pusa-372 proved to be more sensitive to mutagenic treatment than the var. Pusa-212.
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DOI: 10.3923/ajps.2009.318.321
URL: https://scialert.net/abstract/?doi=ajps.2009.318.321
INTRODUCTION
The generation of genetic variability by induced mutagenesis provides a base for strengthening plant improvement programs. Various classes of physical and chemical mutagens differ in their efficiency in inducing mutations and in the spectrum of mutations induced. Combination of different mutagens, if their mutagen induction process is independent and capable of interaction, should increase the mutation frequency and alter the mutation spectrum. While, ionization radiations still remain the most suitable agents for inducing genetic variability (Tah, 2006; Sangsiri et al., 2005; Joseph et al., 2004; Irfaq and Nawab, 2003; Bhatia et al., 2001; Brunner, 1995) a number of chemicals have been found to be equally and even many times more effective and efficient mutagens (Ganapathy et al., 2008; Dhanavel et al., 2008; Basu et al., 2008; Rekha and Langer, 2007; Solanki, 2005; Kharkwal, 1998a; Thakur and Sethi, 1995).
The traditional varieties of chickpea have low potentiality and restricted variability with respect to economic characters. Broadening the genetic base for crop improvement can be quickly achieved through induced mutagenesis. The parameters of M1 generation help in comparing the effectiveness and efficiency of mutagens, besides identifying the plants with maximum genetic damage that are likely to carry the high frequency of micro mutations in M2 and M3 generations. For any mutation-breeding program, selection of effective and efficient mutagen is very essential to recover high frequency of desirable mutations (Solanki and Sharma, 1994). Hence, the basic information on mutagenic sensitivity, efficiency of mutagens, methods of handling the material and treatment methods required to maximize mutation induction is essential for success in any mutation-breeding program. The present study was undertaken to understand the response of chickpea genotypes to physical and chemical mutagens with a view to identify mutagenic treatments inducing maximum frequency of mutations in M2 generation.
MATERIALS AND METHODS
The materials used for this comparative study of effectiveness and efficiency comprised of two varieties of chickpea (Cicer arietinum L.) viz. Pusa-212 and Pusa-372. Dry seeds (10-12% moisture content) of both the varieties were irradiated from a 60Co source at NBRI lucknow with a dose of 150, 200, 300 and 400 Gy. Another set of presoaked seeds in distilled water (12h) was treated with EMS at different concentrations (0.1, 0.2, 0.3 and 0.4%) prepared in sodium phosphate buffer with 7.0 pH for 6 h with constant intermittent shaking. A portion of seeds irradiated at 200 and 300 Gy gamma ray doses were also treated with 0.2% and 0.3% EMS independently for 6 h. A total of 13 treatment combinations (including control) were evaluated separately for each variety in RBD with three replications during the rabi season of 2001-2002 at the Agriculture Field Station, Aligarh Muslim University, Aligarh (India). Each treatment consisted of 300 seeds with 100 seeds in each plot of 3x3 m size. The seed to seed and row to row distance was maintained at 15 and 20 cm, respectively. Data on various biological parameters such as seed lethality (L), seedling injury (I), pollen sterility (S) and meiotic aberrations (M) were recorded in M1 generation (Wani and Anis, 2002). Each M1 plant was harvested separately and M2 generation was raised from a composite sample made by bulking 30 seeds from each M1 harvested plant of a treatment over all the replications. The M2 population was also evaluated in RBD with three replications, each replication plot consisting of 500 seeds, with a total of 1500 seeds in each treatment as well as in control in both the varieties. The M2 population was carefully screened for various chlorophyll mutations (Wani and Anis, 2004). The mutagenic effectiveness and efficiency was calculated on the basis of formula suggested by Konzak et al. (1965).
Mutagenic effectiveness:
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Mutagenic efficiency:
RESULTS AND DISCUSSION
Perusal of the results (Table 1, 2) revealed that the effectiveness of various mutagens and the response of varieties to different mutagens were varying. In case of gamma rays, the effectiveness increased with an increase in dose from 150 to 400 Gy in the var. Pusa-212, whereas it decreased beyond the dose of 300 Gy in the var. Pusa-372. Among EMS treatments, effectiveness initially increased with an increase in concentration but decreased at higher treatments (0.4% EMS) in both the varieties. Among combination treatments, 200 Gy+0.3% EMS was most effective in both the varieties. In general, EMS proved to be more effective in causing mutations as compared to gamma rays and the combination treatments. The gamma rays were least effective in this regard. Among the two varieties, the response to mutagenic effectiveness was more in the var. pusa-372 than in the var. Pusa-212.
The mutagenic efficiency seemed to vary depending on the criteria selected for its estimation and the degree of efficiency of various mutagens also showed variation (Table 1, 2). The efficiency calculated on the basis of seedling injury was generally higher followed by the efficiency based on meiotic aberrations as compared with that based on lethality and sterility in both the varieties of chickpea. Mutagenic efficiency increased with an increase in the dose of gamma rays in the var.
Table 1: | Mutagenic effectiveness and efficiency of gamma rays, EMS and their combination treatments in chickpea (Cicer arietinum L.) var.Pusa 212 |
Mf: Total chlorophyll mutation frequency in M2 generation. Dose: Gray (Gy) for gamma rays, timexconc. for EMS and Gyxtimexconc. for combined treatments |
Table 2: | Mutagenic effectiveness and efficiency of gamma rays, EMS and their combination treatments in chickpea (Cicer arietinum L.) var.Pusa 372 |
Mf: Total chlorophyll mutation frequency in M2 generation. Dose: Gray (Gy) for gamma rays, timexconc. for EMS and Gyxtimexconc. for combined treatments |
Table 3: | Mutation rate of different mutagens in relation to biological effects such as lethality, sterility, injury and chromosomal aberrations in chickpea (Cicer arietinum L.) |
MRL: Mutation rate base on lethality, MRS: Mutation rate based on sterility, MRI: Mutation rate based on injury, MRM: Mutation rate based on chromosomal aberrations |
Pusa-212 except in case of lethality, where it decreased at 400 Gy.
Contrarily, in the var. Pusa-372, mutagenic efficiency increased up to 300 Gy dose but decreased at highest dose (400 Gy) for all the criteria used. In case of EMS, 0.2 and 0.3% treatments were more efficient than the lower and higher treatments in both the varieties, with a few exceptions.
Combination treatments did not show any regular trend, however, 300 Gy+0.2% EMS proved to be most efficient based on lethality, sterility and seedling injury, whereas, 200 Gy+0.2% EMS was the most efficient treatment based on meiotic aberrations.
Mutation rate (Table 3) based on lethality, sterility and injury was highest among the combination treatments in both the varieties. The EMS in turn was more efficient than gamma rays. However, EMS turned out to be most efficient on the basis of meiotic aberrations in the var. Pusa-212 and was comparable to combination treatments in the var. pusa-372. Gamma rays appeared to be least efficient for all the criteria used.
The usefulness of a mutagen depends both on its effectiveness and efficiency, efficient mutagenesis being production of maximum desirable changes accompanied by the least possible undesirable changes. Mutagenic effectiveness is a measure of frequency of mutations induced by unit dose of mutagen, where as mutagenic efficiency is indicative of proportion of mutations as against undesirable biological effects such as gross chromosomal aberrations, lethality and sterility (Konzak et al.,1965). A common observation in the present study revealed that the degree of effectiveness and efficiency varied between different mutagens and also between the two varieties. Similar differences in mutagenic response have also been reported by many workers (Dhanavel et al., 2008; Bhat et al., 2007; Kharkwal, 1998a). In the present study, lower or intermediate dose treatments proved to be more effective and efficient. The decrease in effectiveness at higher dose treatments may be attributed to the failure in proportional increase of mutation frequency with the increase in dose/conc. of the mutagens. The higher efficiency at lower and intermediate doses of mutagens as observed in the present study might be due to the fact that the biological damage (injury, lethality, sterility etc.) increased with an increase in dose at a rate greater than the frequency of mutations (Konzak, 1965). Greater effectiveness and efficiency of lower or intermediate treatments of chemical mutagens alone or in combination with gamma rays has also been reported earlier (Dhanavel et al., 2008; Kharkwal, 1998a; Singh and Singh, 2007; Khan et al., 2005; Thakur and Sethi, 1995).
Besides, many workers as mentioned above have also observed variations in mutagenic efficiency based on different criteria used as observed in the present study. According to Konzak et al. (1965), the reason for greater efficiency of lower doses/treatments is due to the fact that the biological damage such as injury, lethality and sterility increases with the increase in mutagenic treatments at a faster rate than the mutations. In other words lower or intermediate doses/concentrations cause relatively less damage enabling the organism to express the induced mutations successfully. It could be well stated here that while physical mutagens have been exploited to a greater extent for inducing mutations in crop plants and majority of the varieties released through induced mutations belong to physical mutagens. However, some genotypes in crop plants respond more to chemical mutagens than physical ones and in such genotypes appropriate dose/concentration followed by efficient handling of the mutagenised population could yield better results in terms of economic traits like yield, adaptability, protein content etc.
An overview of the above discussion reveals that the two varieties of chickpea used in the present study have proved to be highly responsive to chemical mutagens alone as well as in combination with gamma rays. The intermediate doses of gamma rays (200 and 300 Gy), EMS (0.2 and 0.3%) and lower combination treatments (200 Gy+0.2% EMS, 300 Gy+0.2% EMS) are here recommended for exploiting variability and isolating promising mutants in chickpea in general and the present two varieties in particular.
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