Assessment of radiosensitivity and enhancing key steviol glycosides in Stevia rebaudiana Bertoni through gamma radiation

Abstract

Purpose

Stevia rebaudiana Bertoni is a perennial herb, widely used as a natural sweetener around the globe. The key compounds responsible for its sweetness includes stevioside and rebaudioside-A. In order to improve these steviol glycosides, the present study was initiated to study the effect of induced mutagenesis on growth parameters, steviol glycosides and nuclear DNA content in Stevia rebaudiana Bertoni using ten doses of gamma-rays (5-100 kR).

Materials and methods

Healthy seeds of ‘Madhuguna’ variety of Stevia rebaudiana Bertoni developed and maintained at stevia breeding farm, Agrotechnology division, CSIR-Institute of Himalayan Bioresource Technology, Palampur (HP), India were irradiated with ten doses of gamma rays (600 seeds each/dose) ranging from 5 kR to 100 kR (i.e., 5, 10, 15, 20, 30, 40, 50, 60, 80 and 100 kR) using Co⁶⁰ gamma irradiation chamber at CCS Haryana Agricultural University, Hisar, (Haryana), India.

Results

Significant variations were recorded for all the seedling traits studied while major impact was noticed on the seedling after reaching the cotyledonary stage and doses above 40 kR showed absolute mortality of the seedlings. Based on probit analysis, the optimum LD₅₀ dose lies in the range of 20-23 kR. Glycosidic profiling of 296 mutants using high-performance liquid chromatography showed decreased total steviol glycoside content with increased radiation dose. Doses 5 kR and 10 kR, were found to be effective in increasing the overall glycosidic content. A total of 72 promising mutants were also screened for increased rebaudioside-A stevioside ratio. Comparison of nuclear DNA content using flow cytometry revealed a similar decrease in the total nuclear DNA content with increase in dosage of gamma rays. The average genome size at 5, 10, 15, 20 and 30 kR treatments were 2.72, 2.69, 2.68, 2.70 and 2.66 pg as compared to 2.72 pg in control.

Conclusions

Mild dose of gamma rays (5 and 10 kR) in stevia were found to be effective in improving the mean steviol glycoside content and may be used in future stevia mutation programmes.

Keywords:

• Gamma rays
• probit
• steviol glycoside
• stevioside
• rebaudioside-A
• flow cytometry

Acknowledgements

The authors are grateful to the Director, CSIR-IHBT, Palampur, for providing necessary facilities and financial support through MLP 0128 for this study. The authors are also thankful to CCS Haryana Agricultural University, Hisar, (Haryana), India for providing gamma irradiation facility. The CSIR-IHBT communication number of this article is ‘5589’.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The author(s) reported there is no funding associated with the work featured in this article.

Notes on contributors

Ashok Kumar

Ashok Kumar is Principal Scientist in the Agrotechnology Division, Council of Scientific and Industrial Research - Institute of Himalayan Bioresource Technology, Palampur (H. P.), India.

Satbeer Singh

Satbeer Singh is Scientist in the Agrotechnology Division, Council of Scientific and Industrial Research - Institute of Himalayan Bioresource Technology, Palampur (H. P.), India.

Amit Rana

Amit Rana is working as Senior Project Associate in the Agrotechnology Division, Council of Scientific and Industrial Research - Institute of Himalayan Bioresource Technology, Palampur (H. P.), India.

Pawan Kumar

Pawan Kumar is Assistant Scientist in the Genetics and Plant Breeding Department, Chaudhary Charan Singh Haryana Agricultural University, Hisar (Haryana), India

Shashi Bhushan

Shashi Bhushan is Senior Principal Scientist in the Biotechnology Division, Council of Scientific and Industrial Research - Institute of Himalayan Bioresource Technology, Palampur (H. P.), India.

Vijay Lata Pathania

Vijay Lata Pathania is Senior Technical Officer in the Chemical Technology Division, Council of Scientific and Industrial Research - Institute of Himalayan Bioresource Technology, Palampur (H. P.), India.

Dinesh Kumar

Dinesh Kumar is Principal Scientist in the Chemical Technology Division, Council of Scientific and Industrial Research - Institute of Himalayan Bioresource Technology, Palampur (H. P.), India.

Sanatsujat Singh

Sanatsujat Singh is Senior Principal Scientist in the Agrotechnology Division, Council of Scientific and Industrial Research - Institute of Himalayan Bioresource Technology, Palampur (H. P.), India.

Rajesh Kumar Arya

Rajesh Kumar Arya is Assistant Scientist in the Genetics and Plant Breeding Department, Chaudhary Charan Singh Haryana Agricultural University, Hisar (Haryana), India