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Effect of gamma-radiation and sodium azide on quantitative characters in rice (Oryza sativa L.)

Abstracts

Seeds of rice cultivar IAC-1246 received single and combined treatments of 10 or 20 Krad gamma-rays and 0.5 mM sodium azide (SA). The experiments were carried out to assess the effect of treatments on the mean and variance in second generation plants of the following quantitative traits: number of days to flowering (NDF), culm length (CL) and tiller number (TN). In general, the mutagenic treatments increased variance, but did not change the mean for the characters NDF and CL in the M2 generation. There was no increase in the mean or variance of TN. The combined treatments of gamma-rays and SA resulted in larger variance in CL than for the treatments with gamma-rays alone, but not higher than obtained with SA alone. Combined treatments with gamma-rays and SA did not increase the variance of NDF and TN when compared with the corresponding single treatments.


Sementes do cultivar de arroz IAC-1246 receberam tratamento individual e combinado de 10 e 20 Krad de raios-gama e 0,5 de azida sódica (SA). O experimento foi realizado para avaliar o efeito dos tratamentos sobre a média e a variância de plantas M2 nos seguintes caracteres quantitativos: número de dias para a maturação (NDF), comprimento de colmo (CL) e número de perfílhos (TN). Em geral, os tratamentos mutagênicos incrementaram a variância, sem mudar a média para os caracteres NDF e CL na geração M2. Todavia, não foi encontrado nenhum incremento seja para a média ou para a variância no caráter TN. Para o caráter CL, os tratamentos combinados de raios-gama e SA mostraram maior variância que aquela observada no tratamento individual com raios-gama, não sendo superior que aquela correspondente ao tratamento individual com SA. Para os caracteres NDF e TN, os tratamentos combinados de raios-gama e SA não incrementaram a variância, quando comparados aos correspondentes tratamentos individuais.


Oryza sativa L.)

** Part of a thesis presented by R.M. to the Escola Superior de Agricultura "Luiz de Queiroz", Universidade de São Paulo, in partial fulfillment of the requirements for the Doctoral degree.

Ricardo Montalván and Akihiko Ando

Departamento de Genética, Escola Superior de Agricultura" Luiz de Queiroz", Universidade de São Paulo, Caixa Postal 83, 13400 Piracicaba, SP, Brasil. Send correspondence to R.M.

The present address of R.M. is Departamento de Agronomia, CCA, Universidade Estadual de Londrina, Campus Universitário, Caixa Postal 6001, 86051-970 Londrina, PR, Brasil.

ABSTRACT

Seeds of rice cultivar IAC-1246 received single and combined treatments of 10 or 20 Krad gamma-rays and 0.5 mM sodium azide (SA). The experiments were carried out to assess the effect of treatments on the mean and variance in second generation plants of the following quantitative traits: number of days to flowering (NDF), culm length (CL) and tiller number (TN). In general, the mutagenic treatments increased variance, but did not change the mean for the characters NDF and CL in the M

2 generation. There was no increase in the mean or variance of TN. The combined treatments of gamma-rays and SA resulted in larger variance in CL than for the treatments with gamma-rays alone, but not higher than obtained with SA alone. Combined treatments with gamma-rays and SA did not increase the variance of NDF and TN when compared with the corresponding single treatments.

INTRODUCTION

Breeding for quantitative characters is successful when there is genetic variability in the populations. According to Scossiroli (1970), in some cases genetic progress for yield, which is of a quantitative nature, is difficult because population variability has already been intensely exploited. Additionally, there is a narrow genetic base in the main crops, such as rice (Cuevas-Pérez

et al., 1992) and soybean (Hiromoto and Vello, 1986).

The use of physical and chemical mutagens, or a combination of both, has been an important tool for the increase of variability in agronomic traits. Ree (1970) treated rice with X-rays and thermal neutrons separately to obtain mutants with short culm and to improve other agronomic traits. The average culm length of the selected plants was significantly shorter than in the original variety. Also the variation in culm length and other desirable characters showed a wider range than in the original cultivar.

Mutation induction as a way of increasing genetic variability for quantitative traits has been studied in a wide variety of species. Miah and Bhatti (1968), while working with the second generation after seed mutagenic treatment (M2 population) of two irradiated rice cultivars, found that in general the averages for leaf length and number of grains/cm3 were almost the same as in the control populations. However, the variation of the irradiated population was larger than in the controls. Oka et al. (1958), Matsuo and Ozonawa (1960), Jana and Roy (1973), among others, also reported an increase in variation without an apparent mean change in polygenic traits in rice. Jana and Roy (1973) found a considerable variation increase of tiller number, panicle length and grain yield per plant in the M2 generation, compared with control plants.

Rawling et al. (1958) found significant genetic variability in yield, plant height, maturity and seed size in soybean plants, grown from seeds irradiated with thermal neutrons and X-rays. The estimated genetic variance for radiation treatments was on average five times greater than in the control.

Rubaihayo (1976) obtained mutants for resistance to dehiscence, reduced height and prematurity in irradiated soybeans. These mutants showed high productivity in the M2, M3 and M4 generations; one of them produced 40% more than the control.

An increase in genetic variance of quantitative characters has been induced by irradiating cowpeas (Araújo, 1987) lentils (Sharma and Sharma, 1984) and wheat (Kumar, 1977). However, Emery and Wynne (1976) could not find any evidence of yield improvement in the M2 to M6 generations in irradiated of peanuts.

Gamma-ray and ethyl methane sulfonate (EMS) treatments increase variation in heading date and straw length in the M2 families of barley (Aasveit, 1967). The highest variances in heading date were obtained with gamma-rays and combined treatments. Only small changes were observed in average straw length, and higher dosages of gamma-rays, and combined treatments, reduced variation when compared with lower dosages.

The present study was carried out in order to analyze the influence of single and combined treatments of gamma-rays and sodium azide on mean value and variance of some quantitative characters of rice in the M2 generation.

MATERIAL AND METHODS

Five hundred fertile dormant rice seeds of variety IAC-1246 were submitted to single and combined treatments of 10 or 20 Krad of gamma-rays and/or 0.5 mM sodium azide (SA). Irradiation at a dose rate of 139.3 Krad/h with a

60Co source was applied at the Nuclear Energy Center for Agriculture (CENA), Piracicaba, São Paulo. Chemical treatments were carried out by immersion of seeds in 250 ml of freshly prepared 0.5 and 1.0 mM solutions of SA (buffered at pH 3.0) for 8 h with continuous agitation at 25 ± 2

oC. Immediately after treatments, the seeds were thoroughly washed in tap water. In combined treatments, SA was applied immediately after irradiation.

The following treatments were used:

T1 = control pH7 (material treated only with pH 7.0 water)

T2 = 10 Krad gamma-rays

T3 = 20 Krad gamma-rays

T4 = control pH3 (material treated only with pH 3.0 water)

T5 = 0.5 mM sodium azide

T6 = 10 Krad gamma-rays and 0.5 mM sodium azide

T7 = 20 Krad gamma-rays and 0.5 mM sodium azide

Treated seeds were planted in pots in the greenhouse, and 30-day-old seedlings were transplanted individually to the field. Spacing was 15 cm between plants and 80 cm between rows. The M1 plants were harvested separately. Each treatment consisted of an average of 638 M1 panicles. All M2 seeds of the same treatment were mixed. One thousand and five hundred fertile M2 seeds were sampled at random and sown in plastic boxes containing fertile soil. Three repetitions of 343 M2 seedlings each (on average) per treatment were transplanted 30 days after sowing. A randomized complete block design was used. The experimental plot consisted of one 35 m row with 10 cm spacing between plants and 50 cm betweeen rows. One hundred and seventy plants were randomly sampled for assessment in each replication.

The following traits were observed in each M2 plant: culm length (CL): measured from the plant base to the last culm node one week before harvesting; number of days to flowering (NDF): number of days from seeding to the first opened flower; tiller number (TN): number of fertile tillers.

Mean value, standard deviation, variance, and coefficient of variation (CV) of each trait were estimated. The relative coefficient of variation was estimated based on the variation coefficient of the mutagen-treated population (CVt) and the non-treated control sample (CVnt) (Morsi et al. 1977), which allows an estimation of the variation induced by the treatment. The "F" test (Rawling et al., 1958; Joshi and Frey, 1967) was used to determine the significance of the increase of genetic variance attributed to mutagen treatment, where

"F" = variance among plants from the treatment

variance among plants from the control

The difference between the residual variances of the mutagen treatments and that of the control sample, according to Ando and Vencovsky (1967), gives an estimation of the variance increase due to mutagenic treatment; thus this difference was also calculated:

Dt = sr2 - so2

where, Dt = variance increase due to the mutagenic treatment, sr2= mutagenic treatment residual variance, so2²= control residual variance.

RESULTS AND DISCUSSION

The analysis of variance of the M

2 generation for all traits did not show any significant difference among treatments by the F test (

Table I). The differences in the means between the control samples and the treatments were negligible, indicating that the means were not affected by the mutagenic treatments. Oka

et al. (1958) found no significant changes in average plant height and number of days to flowering in four generations derived from X-irradiated rice seeds. However, Jana and Roy (1973) found a significantly lower mean tiller number in rice treated with EMS. The low magnitude of coefficients of variation obtained for all traits in our experiment indicates that there was reasonable accuracy (

Table I).

Table I
- Variance, mean value and coefficient of variation (CV) of three quantitative traits analyzed in the M2 generation, originating from gamma-ray and sodium azide treatments of rice.

ns: Not significant.

The percentage change in the mean of the treatments in relation to the control was minimal, and the standard error of the means was small for the CL and NDF traits, but large for the TN trait (Table II). The amplitude of variation was significantly increased in some treatments when compared with the control. The combined treatment (20 Krad gamma-rays + 0.5 mM SA) gave the lowest amplitude of variation in the CL trait and the highest amplitude of variation in the NDF trait. The TN trait did not undergo any important change in amplitude of variation in all treatments, while the combined treatments tended to increase the amplitudes of CL and NDF, decreasing the minimum of CL and increasing the maximum in NDF.

Treatment (Gamma-rays (Krad) + SA (mM))Mean ± SE% of the control (pH 7.0)CV (%)CVt/CVntAmplitude of variationCulm lengthControl (pH 7) 0 + 080.58 ± 7.771009.741.0055-10010 + 081.59 ± 7.591019.220.9555-10320 + 082.30 ± 8.721029.801.0151-102Control (pH 3.0) 0 + 084.48 ± 7.321059.620.9943-1020 + 0.578.38 ± 9.579711.121.1447-10210 + 0.581.61 ± 8.7910110.921.1245-10620 + 0.579.66 ± 9.619911.661.2038-104Days to floweringControl (pH 7.0) 0 + 0101.02 ± 3.451002.911.0092-10010 + 0102.33 ± 4.301014.381.5093-12320 + 0101.94 ± 4.001013.881.3388-120Control (pH 3.0) 0 + 0101.35 ± 3.241003.411.1794-1260 + 0.5102.39 ± 4.281014.121.4293-13810 + 0.5100.49 ± 3.83994.021.3891-13120 + 0.5100.73 ± 4.571003.851.3291-141Tiller numberControl (pH 7.0) 0 + 06.28 ± 2.5910044.061.001-1810 + 06.51 ± 2.6610440.330.911-1520 + 06.59 ± 2.7210541.680.951-20Control (pH 3.0) 0 + 07.27 ± 2.9011638.210.871-180 + 0.56.72 ± 2.6010739.180.891-2010 + 0.56.73 ± 2.6510740.820.931-2020 + 0.56.43 ± 2.7010241.890.951-17

Table II - Mean and standard error (SE), coefficient of variation (CV), relative coefficient of variation (CVt/CVnt)* and amplitude of variation for three quantitative traits in the M2 generation of the rice cultivar IAC-1246, treated with gamma-rays and sodium azide (SA).

*CVt = coefficient of variation among plants from the mutagenic treatment.

CVnt = coefficient of variation among plants from the control treatment.

The coefficient of variation was increased when calculated based on information collected from individual plants (Table II), compared with the coefficient of variation that was calculated based on the averages (Table I). Even at high absolute values, the coefficient of variation of the CL and NDF was still of low magnitude, showing a reasonable approximation to the mean. However, the coefficient of variation in TN increased, with a corresponding high standard error for this trait.

TN had values inferior to 1, indicating a decrease of variance in relation to the control, but traits CL and NDF had values superior to 1 for relative coefficient of variation of the different treatments, indicating an increase of variance in these treatments.

The increase of variance in the treated population (Table III) is an important indication of the efficiency of mutagen treatment in inducing genetic variability. However, the measured variance for the M2 generation involves the genetic variance and the environmental variance, which limits the inference from these data. Aasveit (1967) observed that M2 families are not suitable for experiments on variability and that results obtained with more advanced generations are much more reliable.

Table III
- Phenotypic variance, residual variance, "F" test (Vt/Vnt)a and variance increase due to the mutagenic treatment (Dt)b, estimated for three quantitative characters in the M2 generation of the rice cultivar IAC-1246 treated with gamma-rays and sodium azide (SA).

a) Vt: variance among plants from the mutagenic treatment; Vnt: variance among control plants.

b) Dt = sr2 - so2; sr2 = variance increase due to the mutagenic treatment, so2 = control residual variance.

*: Significant at the 5 % level of probability.

ns: Not significant.

Based on these considerations, data from the M2 generation were not used to calculate genetic parameters. Instead, "F" tests as well as the variance treatment were used to determine the effects of the mutagen treatments (Table III). These data showed that the mutagenic treatments applied were efficient in the amplification of the variances of CL and NDF, but not TN.

Combined treatments effectively increased the variance in the traits CL and NDF, however it was not possible to discern exactly the superiority of the combined treatments over individual performance, because single treatments also were efficient. The variances of combined treatments (Table IV) were not different from those of single treatments for the NDF and TN traits. The variance of the combined treatment (10 Krad gamma-rays + 0.5 mM SA) was significantly higher for the trait CL than that of the 10 Krad gamma-ray treatment, but it was not different from the variance obtained in the 0.5 mM SA treatment. The other combined treatment (20 Krad gamma-rays + 0.5 mM SA) gave a considerably higher variance than with 20 Krad gamma-rays alone although it was not different from the treatment with 0.5 mM SA.

TraitsCombined treatmentSingle treatment10 Krad20 Krad0.5 mM SACulm length10 Krad + 0.5 mM SA1.25*—0.95ns20 Krad + 0.5 mM SA—1.28*1.07nsDays to flowering10 Krad + 0.5 mM SA0.81ns—0.88ns20 Krad + 0.5 mM SA—1.08ns0.95nsTiller number10 Krad + 0.5 mM SA1.06ns—1.07ns20 Krad + 0.5 mM SA—0.97ns1.06ns

Table IV - "F" test (Vtc/Vti) among phenotypic variances of single treatments (Vti) and combined treatments (Vtc) estimated for three quantitative traits in the M2 generation of the rice cultivar IAC-1246 treated with gamma-rays and/or sodium azide (SA).

*: Significant at the 5 % level of probability.

ns: Not significant.

In conclusion, a) gamma-ray and SA mutagenic treatments were efficient in increasing variability (variance) in the M2 generations of the CL and NDF traits, but not for TN; b) the SA treatment gave a greater variability for CL than the gamma-rays treatment, and c) the gamma-rays and SA combined treatment did not increase the NDF or the TN trait variability when compared with the corresponding individual treatments.

ACKNOWLEDGMENTS We wish to thank the Nuclear Energy Center for Agriculture (CENA), São Paulo University, Piracicaba, São Paulo, Brazil, for mutagen treatments, and the National Council of Scientific and Technological Development (CNPq), Ministry of Science and Technology, for financial support of the experiment. Publication supported by FAPESP. RESUMO Sementes do cultivar de arroz IAC-1246 receberam tratamento individual e combinado de 10 e 20 Krad de raios-gama e 0,5 de azida sódica (SA). O experimento foi realizado para avaliar o efeito dos tratamentos sobre a média e a variância de plantas M

2 nos seguintes caracteres quantitativos: número de dias para a maturação (NDF), comprimento de colmo (CL) e número de perfílhos (TN). Em geral, os tratamentos mutagênicos incrementaram a variância, sem mudar a média para os caracteres NDF e CL na geração M

2. Todavia, não foi encontrado nenhum incremento seja para a média ou para a variância no caráter TN. Para o caráter CL, os tratamentos combinados de raios-gama e SA mostraram maior variância que aquela observada no tratamento individual com raios-gama, não sendo superior que aquela correspondente ao tratamento individual com SA. Para os caracteres NDF e TN, os tratamentos combinados de raios-gama e SA não incrementaram a variância, quando comparados aos correspondentes tratamentos individuais. REFERENCES

Aasveit, K. (1967). Effects of combinations of mutagens on mutation frequency in barley. In: IAEA/FAO.

Mutat. Plant Breed. II: IAEA, pp. 5-14.

Ando, A. and Vencovsky, R. (1967). The effect of gamma- irradiation on a polygenically inherited character in Nicotiana tabacum L. in relation to selection after treatment of aged seeds. Mutat. Res. 4: 605-614.

Araújo, J.P.P. (1987). Análise genética da variação induzida por radiação gama em caracteres quantitativos de caupi (Vigna unguiculata (L.) Walp.). PhD thesis, Superior College of Agriculture "Luiz de Queiroz", São Paulo University, Piracicaba, SP.

Cuevas-Pérez, F.E., Guimarães, E.P., Berrío, L.E. and González, D.I. (1992). Genetic base of irrigated rice in Latin America and the Caribbean, 1971 to 1989. Crop Sci. 32: 1054-1059.

Emery, D.A. and Wynne, J.C. (1976). Systematic selection for increased fruit yield in populations derived from hybridization only, F1, irradiation, and hybridization following parental irradiation in peanuts (Arachis hypogea L.). Environ. Exp. Bot. 16: 1-8.

Hiromoto, D.M. and Vello, N.A. (1986). The genetic base of Brazilian soybean (Glycine max (L.) Merrill) cultivars. Rev. Bras. Genet. 9: 295-306.

Jana, M.K. and Roy, K. (1973). Induced quantitative mutation in rice. Radiat. Bot. 13: 245-257.

Joshi, S.N. and Frey, K.D. (1967). Genetic variability in oats from recurrent and alternate treatment with physical and chemical mutagens. Radiat. Bot. 7: 513-520.

Kumar, D. (1977). Studies on 60Co gamma-ray induced variability in common wheat cultivar K 68. Egypt. J. Genet. Cytol. 6: 229-243.

Matsuo, T. and Ozonawa, Y. (1960). Studies on mutations induced by radiation and chemicals. Jpn. J. Breed. 10: 223-227.

Miah, A.J. and Bhatti, I.M. (1968). Evolution of new rice varieties by induced mutations to increase yield and resistance to diseases and to improve seed quality. In: IAEA/FAO. Rice Breeding with Induced Mutations (IAEA, ed.). Vienna, pp. 75-96.

Morsi, L.R., Abo-Elenein, R.A. and Mahmoud, I.M. (1977). Studies on the induction of new genetic variability for quantitative traits by gamma-rays and N-nitroso-N- methyl-urethane in barley. Egypt. J. Genet. Cytol. 6: 244-258.

Oka, H.I., Havashi, J. and Shiojiri, I. (1958). Induced mutation on polygenes for quantitative characters in rice. J. Hered. 49: 11-14.

Rawling J.O., Hanway, D.D.G. and Gardner, C.O. (1958). Variation in quantitative characters of soybean after seed irradiation. Agr. J. 50: 524-528.

Ree, J.H. (1970). Induced mutations of rice for short-culm selections in M

2 generation. In: IAEA/FAO.

Rice Breeding with Induced Mutations II (IAEA, ed.). Vienna, pp. 57-67.

Rubaihayo, P.R. (1976). Utilization of gamma-rays for soybean improvement. Egypt. J. Genet. Cytol. 5: 136-140.

Scossiroli, R.E. (1970). Mutations in characters with continuous variation. In: FAO/IAEA. Manual on Mutation Breeding (IAEA, ed.). Technical Report Series, Vienna, 117-123.

Sharma, S.K. and Sharma, B. (1984). Pattern of induced macro and micro-mutations with gamma-rays in lentil. Environ. Exp. Bot. 24: 343-351.

(Received November 18, 1996)

  • Aasveit, K. (1967). Effects of combinations of mutagens on mutation frequency in barley. In: IAEA/FAO. Mutat. Plant Breed. II: IAEA, pp. 5-14.
  • Ando, A. and Vencovsky, R. (1967). The effect of gamma- irradiation on a polygenically inherited character in Nicotiana tabacum L. in relation to selection after treatment of aged seeds. Mutat. Res. 4: 605-614.
  • Araújo, J.P.P. (1987). Análise genética da variaçăo induzida por radiaçăo gama em caracteres quantitativos de caupi (Vigna unguiculata (L.) Walp.). PhD thesis, Superior College of Agriculture "Luiz de Queiroz", Săo Paulo University, Piracicaba, SP.
  • Cuevas-Pérez, F.E., Guimarăes, E.P., Berrío, L.E. and González, D.I. (1992). Genetic base of irrigated rice in Latin America and the Caribbean, 1971 to 1989. Crop Sci. 32: 1054-1059.
  • Emery, D.A. and Wynne, J.C. (1976). Systematic selection for increased fruit yield in populations derived from hybridization only, F1, irradiation, and hybridization following parental irradiation in peanuts (Arachis hypogea L.). Environ. Exp. Bot. 16: 1-8.
  • Hiromoto, D.M. and Vello, N.A. (1986). The genetic base of Brazilian soybean (Glycine max (L.) Merrill) cultivars. Rev. Bras. Genet. 9: 295-306.
  • Jana, M.K. and Roy, K. (1973). Induced quantitative mutation in rice. Radiat. Bot. 13: 245-257.
  • Joshi, S.N. and Frey, K.D. (1967). Genetic variability in oats from recurrent and alternate treatment with physical and chemical mutagens. Radiat. Bot. 7: 513-520.
  • Kumar, D. (1977). Studies on 60Co gamma-ray induced variability in common wheat cultivar K 68. Egypt. J. Genet. Cytol. 6: 229-243.
  • Matsuo, T. and Ozonawa, Y. (1960). Studies on mutations induced by radiation and chemicals. Jpn. J. Breed. 10: 223-227.
  • Miah, A.J. and Bhatti, I.M. (1968). Evolution of new rice varieties by induced mutations to increase yield and resistance to diseases and to improve seed quality. In: IAEA/FAO. Rice Breeding with Induced Mutations (IAEA, ed.). Vienna, pp. 75-96.
  • Morsi, L.R., Abo-Elenein, R.A. and Mahmoud, I.M. (1977). Studies on the induction of new genetic variability for quantitative traits by gamma-rays and N-nitroso-N- methyl-urethane in barley. Egypt. J. Genet. Cytol. 6: 244-258.
  • Oka, H.I., Havashi, J. and Shiojiri, I. (1958). Induced mutation on polygenes for quantitative characters in rice. J. Hered. 49: 11-14.
  • Rawling J.O., Hanway, D.D.G. and Gardner, C.O. (1958). Variation in quantitative characters of soybean after seed irradiation. Agr. J. 50: 524-528.
  • Rubaihayo, P.R. (1976). Utilization of gamma-rays for soybean improvement. Egypt. J. Genet. Cytol. 5: 136-140.
  • Scossiroli, R.E. (1970). Mutations in characters with continuous variation. In: FAO/IAEA. Manual on Mutation Breeding (IAEA, ed.). Technical Report Series, Vienna, 117-123.
  • Sharma, S.K. and Sharma, B. (1984). Pattern of induced macro and micro-mutations with gamma-rays in lentil. Environ. Exp. Bot. 24: 343-351.
  • *
    Part of a thesis presented by R.M. to the Escola Superior de Agricultura "Luiz de Queiroz", Universidade de São Paulo, in partial fulfillment of the requirements for the Doctoral degree.
  • Publication Dates

    • Publication in this collection
      06 Jan 1999
    • Date of issue
      Mar 1998

    History

    • Received
      18 Nov 1996
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