Effect of gamma rays and EMS on plant height and plant spread in annual chrysanthemum

Introduction

Annual chrysanthemum (Chrysanthemum coronarium L.) is one among important commercially cultivated flower crops grown in India. It is a winter season annual, native to Mediterranean region distributed throughout Europe, Northern Africa and Asia and propagated by seeds producing daisy like, golden yellow to white flowers. It is different from florist chrysanthemum in many aspects. The crop is relatively short durated and less photosensitive thus capable of coming up throughout the year. It is hardier, vigorous and grows taller. Its flowers are in various shades of yellow white, having single or double forms. Mutation breeding is one of the established methods by which one can induce variability in vegetatively propagated crops and it also offers advantage over conventional breeding for the improvement of one or more traits within a short span of time. Mutation derived varieties have had a significant impact on the array and choiced of genetic resources available in modern agriculture. Spontaneous mutation or bud sports have played an important role in the evolution of many garden chrysanthemums. In addition to spontaneous mutation, another type of mutation that have a high potential for bringing about the further genetic improvement, is induced mutation through physical and chemical mutagens. The introduction of induced mutation has also attracted considerable attention in chrysanthemums due to the fact that any mutation in dominant genes is easily expressed in the first generation and thus the selection of mutations of directly perceptible characters like flower colour, shape, size etc. is generally very easy and directly be put in commercial use. EMS is a chemical mutagen of the alkylating group and has been widely used in plants because it causes high frequency of gene mutations and low frequency of chromosome aberrations. This mutagen has been used to treat seeds and recently to treat in vitro explants of many species. In India the crop has been naturalized and locally called 'Bijli' in Nagpur (Meshram et al. 2008) [11] , 'Baboona' in Haryana (Mishra et al. 2002) [12] 'Guldhak' in Punjab, 'Market' in Delhi and 'Gendi' in Uttar Pradesh. The major flower growing states in India are Tamil Nadu, Andhra Pradesh, Karnataka (Banglore, Dharwad, Belgaum, Hosur), Maharashtra (Ahmadnagar and Pune), West Bengal, Uttar Pradesh, Haryana, Gujarat and Delhi. The important flowers having more demand are Flowers are sold in market loose as well as cut flowers. Among the flowers used for domestic market, annual chrysanthemum is considered as one of the important commercial loose flower. There is a great scope of increasing area under this crop. Increasing flower yield with quality flowers, extending the duration of flower production are the prime importance in the cultivation of annual chrysanthemum. This can be achieved by proper dose of nutrients.

Materials and Methods

The investigation entitled, "Mutation studies in annual chrysanthemum" was carried out at the field of college garden, Horticulture Section, College of Agriculture, Nagpur during rabi season of the year 2021-22 and 2022-23. The best quality seeds of annual chrysanthemum variety "PDKV Bijli Super" were obtained from, Horticulture Section, College of Agriculture, Nagpur (M.S). The 100 seeds were sown on nursery beds. The seeds of annual chrysanthemum variety PDKV Bijli Super was irradiated with four doses of gamma rays (100 Gy, 200 Gy, 300 Gy and 400 Gy) at chemistry lab of Rashtra Sant Tukdoji Maharaj Nagpur university. The seeds of annual chrysanthemum variety PDKV Bijli Super were selected for treatment. The seeds were treated with different Ethyl methane sulphonate (EMS) concentrations immersed in Ethyl methane sulphonate (EMS) solution for 2 hours. In control, the seeds were immersed in distilled water for 2 hours. After the treatments, the seeds were dipped in STS (sodium thiosulphate) solution (0.3%) for 15 minutes to remove the stresses of the solution on seed. Uniform and healthy seedlings were selected for transplanting. The gamma rays treated seedlings transplanted on 7 th November, 2021. The chemical treated seedlings and untreated seedlings (control) were planted. These seedlings were planted at 45 X 30 cm distance on the experimental field in Randomized Block Design (RBD) of three replications with eight treatments. All the standard cultural practices were followed, except pinching and disbudding operations. The plants that had showed variation were isolated from the population of the M 1 generation and of these variants were transplanted as per induced mutagenic treatments and nontreated control separately on 15 November 2022 as progeny rows to raise the M 2 population. Collect seeds from each variant separately, ensuring proper storage conditions to maintain seed viability. Document the seed collection process, including the quantity and quality of seeds obtained from each variant. Establish a systematic timeline for data collection and observations. Regularly record data points such as plant height, leaf morphology, flowering time, and any other relevant traits to track the development of the M 2 population.

Results and Discussion

The data furnished in Table 1. and graphically illustrated in Fig. 1. had shown the significant influence of the gamma radiation and EMS treatments on the plant height. During M 1 generation at 30 days after transplanting, plant height was decreased due to gamma rays and EMS treated seeds of annual chrysanthemum over control T 1 (26.98cm). Among the induced mutagen maximum plant height (25.47cm) was recorded in the treatment at (0.1%) EMS treatment T 6 which was at par with the treatment T 7 (24.98cm) and treatment T 2 (24.84cm) respectively and minimum (14.17cm) in gamma rays T 5 (400 Gy). At 60 days after transplanting, plant height was decreased due to gamma rays and EMS treated seeds of annual chrysanthemum over control T 1 (59.27cm). Among the induced mutagen maximum plant height (58.16cm) was recorded in the treatment at (0.1%) EMS treatment T 6 which was at par with the treatment T 7 (57.68cm) and treatment T 2 (57.55cm) respectively and minimum (34.21cm) in gamma rays T 5 (400 Gy). At 90 days after transplanting, plant height was decreased due to gamma rays and EMS treated population of chrysanthemum over control T 1 (98.84cm). Among the induced mutagen maximum plant height (96.40cm) was recorded in the treatment at (0.1%) EMS treatment T 6 which was at par with the treatment T 7 (94.03cm) and treatment T 2 (93.79cm) respectively and minimum (71.02cm) in gamma rays T 5 (400 Gy).

M2 generation

The result presented in Table 2 and graphically represented in Fig. 2 had shown significant differences among the progenies of different gamma rays and EMS treatments in respect of plant height on annual chrysanthemum.

As compared to the control treatment T 1 , the mean height of plant was found to be significantly decreased due to the radiation treatment and it was ranged between (68.03cm) to (94.01cm) recorded. The control treatment T 1 had recorded (95.87cm) plant height. Among the induced mutagen maximum plant height (94.01cm) was recorded in the treatment at (EMS @ 0.1%) treatment T 6 at 50% flowering, which was at par with the treatment T 7 (90.18cm) and treatment T 2 (89.82cm) respectively and minimum plant height was (68.03cm) recorded in gamma rays T 5 (400 Gy).

The variance was increased in all the radiation treatments as compared to the control treatment and the maximum variance (115.24) was noticed in the treatment (400 Gy) T 5

and the minimum variance (35.60) was seen in T 1 i.e. control. While in EMS treatment the maximum variance (97.55) was seen in (EMS @ 0.3%) T 8 and minimum (38.19) in (EMS @ 0.1%) T 6 . Whereas, the coefficient of variation was increased in all the radiation treatments than the control treatment. The maximum coefficient of variation (15.05%) was registered in the treatment T 5 (400 Gy) and in the EMS treatment maximum coefficient of variation (11.88%) was noticed in (EMS @ 0.3%) T 8 and minimum (6 . 54%) in (EMS @ 0.1%) T 6 . Similarly, the standard deviation was increased in all the radiation treatments as compared to the control treatment. Significant results were observed with maximum plant height in M 1 generation followed by M 2 generation, irrespective of different doses of gamma rays and EMS. Thus, from the result it is apparent that, in general the gamma rays and EMS treatments had reduced the height of plant as compared to the non-treated plants in both the generations. As the dose of gamma rays and EMS increased, there was a decrease in the height of chrysanthemum plants.

Similarly, the plant height was maximum in M 1 generation as compared to M 2 generation. The decrease in plant height after exposure of the seeds to the EMS and gamma rays has been due to disturbances of chromosomal aberrations and auxin synthesis. The results obtained are in conformity with the findings of Kapadiya et al. (2014) [9] and Vaidya et al.

(2016) [10] in chrysanthemum. Inactivation of auxin and decrease in auxin content with an increase in the radiation dose might be responsible for the reduction of plant height. Moreover, the reduction of plant height was also depends on the nature and extent of chromosomal damage (Banerji and Datta, 2002) [2] .

The data furnished in Table 3 and graphically illustrated in Fig. 3 had shown the significant influence of the gamma radiation and EMS treatments on plant spread which was clearly indicated that plant spread was decreased due to gamma rays and EMS treated population of annual chrysanthemum over control T 1 (68.41 cm) during M 1 generation. Among the induced mutagen maximum plant spread (61.65 cm) was recorded at (0.1% EMS) T 6 . Which was at par with the treatment T 7 (56.33 cm) and treatment T 2 (54.22 cm) respectively and minimum plant spread (34.85 cm) in gamma rays (400 Gy) T 5 .

M2 generation

The result presented in Table 4 and graphically represented in Fig. 4 had shown significant differences among the progenies of different gamma rays and EMS treatments in respect of plant spread of annual chrysanthemum. As compared to the control treatment (T 1 ), the mean plant spread was found to be significantly decreased due to the gamma radiation and EMS treatment and it was ranged between (22.33 cm) to (60.89 cm)

The control treatment (T 1 ) had recorded (66.80 cm) plant spread. Among the induced mutagen maximum plant spread (60.89 cm) was recorded in the treatment at (0.1% EMS) treatment (T 6 ) which was at par with the treatment T 7 (54.96 cm) and treatment T 2 (54.41 cm) respectively and minimum plant spread was (22.33 cm) in gamma rays (400 Gy) (T 5 ).

The variance was increased in all the radiation treatments as compared to the control treatment and the maximum variance (98.09) was noticed in the treatment 400 Gy (T 5 ) and the minimum variance (13.89) was seen in (T 1 ) i.e. control. While in EMS treatment the maximum variance (78.75) was seen in (0.3% EMS) T 8 and minimum (14.07) in (0.1% EMS) T 6 . Whereas, the coefficient of variation was increased in all the radiation treatments than the control treatment.

The maximum coefficient of variation (34.78%) was registered in the treatment 400 Gy (T 5 ) and in the EMS treatment maximum coefficient of variation (19.01%) was noticed in (0.3% EMS) T 8 and minimum (6.16) in (EMS @ 0.1%) T 6. Similarly, the standard deviation was increased in all the radiation treatments as compared to the control treatment.

From the presented data, it is evident that, the treatments of gamma rays (100 Gy, 200 Gy, 300 Gy and 400 Gy) and EMS (0.1%, 0.2% and 0.3%) had significantly reduced the plant spread over the control. Due to increase in the dose of gamma rays and EMS, there was a corresponding reduction in plant spread. The reduced in plant spread may be ascribed due to the less number of branches with the gamma irradiated plants and EMS treated plants. However, Gunckel and Sparrow (1961) [7] explained that, the reduction in plant spread could be due to physiological, morphological and cytological disturbances caused by radiation and EMS. Similar results in chrysanthemum are documented by Gupta et al. (2003) [8] , Sharma et al. (2003) [8] and Dilta et al.

(2006) [5] who reported the significant reduction in the spread of the gamma rays treated plants and the reduction of plant spread was increased with an increase in the dose of gamma rays.

References

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