Harnessing gamma radiation-induced mutagenesis for enhanced essential oil yield and morphological improvement in lemongrass (Cymbopogon flexuosus Nees ex Steud)

Introduction

India possesses a remarkable diversity of plant species, with a significant portion identified as medicinal plants. This has made India a global leader in traditional medicine, particularly Ayurveda, which utilizes herbal remedies for various ailments and is known as the "botanical garden of the world" and is the world's largest producer of medicinal herbs (Grover et al., 2002) [1] . Lemongrass, a valuable aromatic plant, is one of the nine mandated crops for development of appropriate production, protection and processing technologies (ICAR-DMAPR, 2024) [2] . Lemongrass, scientifically known as Cymbopogon spp., is a perennial grass with distinctive aromatic properties and it belongs to the family Poaceae, its three species are identified (Gupta, 1969) [3] viz; Cymbopogon flexuosus, Cymbopogon citratus and Cymbopogon pendulus. It is widely cultivated in India for its essential oil, which is rich in citral, a compound responsible for its lemon-like fragrance (Dutta et al., 2016) [4] . Its oil has been traditionally used for its medicinal properties, including antibacterial, antifungal, and anti-inflammatory effects (Shah et al., 2011) [5] . Conventional breeding methods, while effective for improving certain crops viz. cereals, pulses, oilseed etc. but face limitations when applied to medicinal and aromatic plants like lemongrass. These limitations include low genetic variability, self-incompatibility and the lengthy time required to achieve desired traits. This has prompted researchers to explore alternative approaches. Induced mutagenesis has the ability to improve both quantitative and qualitative qualities in crops in a shorter amount of time than traditional breeding (Lal et al., 2016) [6] . Plant genetic variation, particularly alkaloid content and essential oil quality, as well as the economic aspects of medicinal and aromatic plants, have been demonstrated to be improved via mutation breeding (Kolakar et al., 2018) [7] . It can lead to the development of lemongrass varieties with higher levels of essential oil, including its composition and aroma and certain morphological characteristics. Gamma irradiation utilizing 60 Co, a type of ionizing radiation, has been used effectively in mutation breeding and it is often classified as low light emission transfer (LET) radiation. It can induce genetic changes in plants, leading to a wide range of variations. Studies have shown that gamma radiation treatment can im prove both the oil quality and morphological traits of lemongrass. By keep all the points in view induced mutagenesis had accepted as a tool for improvement of the economic traits of medicinal and aromatic plant especially in vegetative propagated crops (Velmurugan et al., 2020) [8] .

Materials and methods

The present investigation was carried out at College of Horticulture, RVSKVV, Mandsaur in the Malwa plateau region of Madhya Pradesh during 2023-24. The slips of lemongrass were procured from "Herbal Garden" College of Horticulture Mandsaur, Madhya Pradesh in uniform size (15-20 cm long, 2-2.50 girth) and were obtained from wellestablished and healthy clumps. Lemongrass slips were treated with gamma irradiation in the gamma chamber on 18 July 2023 at Nuclear Research Laboratory, IARI, New Delhi. The source of gamma radiation was 60 Co isotope and the capacity gamma chamber was 5000 cc. Nine gamma radiation doses ranging from 1kR to 9kR were used in the study, along with three replications of each dose in CRD (Complete Randomized Design) and a radiation-free control. For comparison, untreated slips were used as a control and planted in the pots. All the desired traits were observed from date of planting to 120 days after planting with a fixed interval of 30 days. Following the data collected during the experiment, the ANOVA approach was used to statistically analyze the significance of various treatments at the 5% level of probability.

Results and discussion

It was confirmed from Figure 1 that, there was no major difference in T 0 -control (2.00 & 5.33 days) and T 2 -2kR (2.00 & 6.33 days) for days to initiation and 50% sprouting, respectively, then the remaining treatments took significantly more days for the same traits. Improved sprouting at lower radiation doses was associated with increased auxin and gibberellin activity, as well as the suppression of the inhibitors. Misra et al. (1983) [9] , Awad et al. (1986) [10] , and Pranom et al. (1986) [11] found similarly minor earliness in sprouting with gamma radiation. Misra et al. (1983) [9] , Awad et al. (1986) [10] , and Pranom et al. (1986) [11] found the same comparatively minor earliness in sprouting with gamma radiation. Moreover, the survival was higher (73.33, 70.00 and 69.67 %) in T 2 -2kR with the advancement of growth stages; the survival percentage decreased over T 0 -control (70.00, 65.67 and 64.00 %) at 60, 90 and 120 days after planting, respectively. This could be because gamma radiation positively impacts lemongrass. However, Roongtanakial et al. (2012) [12] likewise showed a decrease in the survival percentage in vetiver grass as gamma radiation doses were raised. The antagonistic impact of gamma radiation on grass may be the cause of variations in survival percentage as radiation doses rise. According to Mutlu et al. (2015) [13] , higher gamma radiation doses have a well-known effect on lowering survival rates in Bermuda grass. Similar results have been found in other Poaceae species (Krishna et al., 1984; Zaka et al., 2002) [14,15] . Different doses of gamma radiation had a notable effect on morphological parameters across life-span stages. Figure 2 indicates that, the incorporation of the gamma radiation causes no major impact on plant height, and number of tillers as the maximum plant height (50.92, 60.59 and 73.40 cm), stem length (9.73, 51.09 and 64.20 cm), girth of stem (4.37, 4.51 and 5.41 mm), number of tillers (6.44, 7.22 and 7.97) number of internodes (2.33, 4.39 and 5.39) and length of internodes (3.46, 11.49 and 11.79 cm) were recorded in T 0 -control while, minimum plant height (23.45, 25.16, 25.33 and 34.28 cm) and stem length (4.11, 15.83 and 25.08 cm) and girth of stem (3.28, 3.50 and 4.32 mm) number of tillers (1.00, 2.17, 2.72 and 3.06) number of internodes (1.00, 1.89 and 2.89) and length of internodes (2.70, 8.38 and 8.68 cm) in T 9 -9kR and both were drastically decreased with the increment in gamma radiation doses at 60, 90, and 120 days after planting, respectively. The results showed similarities with the findings of Lal et al. (2000) [16] . According to Misra et al. (1983) [9] , mutagens disrupt the action of enzymes, which are essential for several plant metabolic processes that lead to improved plant development. According to Kainthura et al. (2015) [17] , a reduction in the amount of auxin in leaves as a result of the enzyme system being destroyed or the enzyme system being inhibited by various radiation dosages may lead to a reduction in the vegetative growth of crops. Different doses of gamma radiation significantly influenced all the leaf parameters and data are shown in ), fresh weight of leaf (0.19, 10.40, 22.40 and 32.52 g) and dry weight of leaf (0.06, 3.12, 6.72 and 9.76 g) were recorded in T 9 -9kR at 60, 90 and 120 days after planting, respectively. This variation may be related to the inherent genetic traits of the various cultivars and varying rates of photosynthesis (Pandey et al., 2012) [18] , as well as environmental influences (Safeena et al., 2019) [19] . Both cell elongation and uneven cell wall growth are responsible for the difference in leaf length with an increase in gamma dose. DNA damage, variances in cell division, and alterations in cell structure and metabolism are just a few of the many effects that gamma radiation can have on plant tissues. According to Reiter et al. (1993) [20] and Takahashi et al. (1995) [21] , the aforementioned effects can cause disturbances in typical growth and development processes. The various gamma radiation dosages had a considerable impact on all yield parameters. The notable variations in the lemongrass were observed from Table 1 due to the induction of gamma radiation on lemongrass slips. There was no change in original leaf pigment in T 1 -1kR to T 5 -5kR and similar to T 0 -control (green), but changed from green to yellowish green from treatment T 6 -6kR onwards, while, stem pigment was changed from yellowish green to purplish green and purple in different doses of gamma radiation. The change in pigmentation may be due the enhancement of the gamma radiation doses as they alter the morphology of pigmenting cells (Mutlu et al., 2015) [13] . Among all the consequences, we found that highest herbage (11100 kg ha -1 ), oil yield (44.10 kg ha -1 ) and oil percent (0.397 %) were in T 2 -2 kR though, the minimum herbage yield (6110 kg ha -1 ) and oil yield (11.60 kg ha -1 ) were taken by treatment T 9 -9kR while, oil percent (0.223 %) was taken by T 8 -8kR. Although radiation reduces growth characteristics, it can change oil quality and increase oil content (Lal et al., 1998) [22] . Chemical and physical mutagens can generate economic trait variability in a variety of crops (Lal et al., 2018) [23] . Low levels of gamma radiation have a major impact on the yield of different crops, according to research by Fowler et al. (1972) [24] . Vinutha et al. (2014) [25] also reported the fluctuation in essential oil yield with sUV-B treatment. Mentha piperita (Maffei et al., 2000) [

, Ocimum basilicum (Jhonson et al., 1999, Nitz and Schnitzler, 2004) [27] , and Mentha spicata (Karousou et al., 1998) [28] all demonstrated an increase in oil yield with short daily sUV-B treatment.

Conclusion

The properties of aromatic crops and their yield of essential oils were significantly impacted by the influence of gamma radiation-induced mutation. However, the current study concluded that, of all the gamma radiation doses applied, the yield attributes were found to be higher than control with T 2 -2 kR dose of gamma radiation. Accordingly, T 2 -2 kR is the optimum dose of gamma radiation for lemongrass, and minor changes were also noted in the pigmentation of the leaves and stem. However, we found that the LD 50 dose for every characteristic of lemongrass under study was greater than 6 kR.

Acknowledgement

AcknowledgementsAuthors regards to express their gratitude to Dean, College of Horticulture, Mandsaur and Director Instruction, Rajmata Vijayaraje Scindia Agriculture University, Gwalior, for their support during the course of experiment.

References

1. Grover JK, Yadav S, Vats V. Medicinal plants of India with antidiabetic potential. J. Ethnopharmacol. 2002;81(1):81-100.
2. ICAR-DMAPR. ICAR-Directorate of Medicinal and Aromatic Plants Research. Available at: https://dmapr.icar.gov.in. 2024.
3. Gupta BK. Studies in the genus Cymbopogon. I. Chromosome studies in Indian Cymbopogon. Proc. Indian Acad. Sci. 1969;70:241-247.
4. Dutta S, Munda S, Lal M, Bhattacharyya PR. A short review on chemical composition, therapeutic use and enzyme inhibition activities of Cymbopogon species. Indian J. Sci. Technol. 2016;9(38):1-9.
5. Shah G, Shri R, Panchal V, Sharma N, Singh B, Mann AS. Scientific basis for the therapeutic use of Cymbopogon citratus (Stapf). J. Adv. Pharm. Technol. Res. 2011;2(1):3-8.
6. Lal M, Dutta S, Bhattacharyya PR. Development of a new superior variety (Jor Lab C-5) of Java citronella with characteristics of stable and high oil yield. Ann. Biol. 2016;32(1):22-23.
7. Kolakar SS, Nadukeri S, Jakkeral SA, Lakshmana D, Hanumanthappa M, Gangaprasad S. Role of mutation breeding in improvement of medicinal and aromatic crops. J. Pharmacogn. Phytochem. 2018;7(3S):425-429.
8. Velmurugan M, Anand M, Sivakumar V, Rajamani K, Pugalendhi L. Induced mutagenesis in medicinal and aromatic plants. In: Advances in Horticulture. 2020:43-60.
9. Misra RL, Bajpai PN. Mutational studies in gladioli (Gladiolus grandiflorus L.). Effect of physical and chemical mutagens on sprouting and survival of corms. Haryana J. Hortic. Sci. 1983;12:1-6.
10. Awad ARE, Elbahr K. Growth regulators and gamma irradiation treatments affecting the sprouting and endogenous hormones in gladiolus. Acta Hortic. 1986;177(2):612.
11. Pranom P, Sangtham K, Orwan M. Production of gladiolus: Effect of gamma irradiation on certain characteristics of gladiolus var. Spic and Span and Norwich Canary. Res. Rep. Kasetsart Univ. 1986;85:1-5.
12. Roongtanakiat N, Jompuk P, Rattanawongwiboon T, Puingam R. Radiosensitivity of vetiver to acute and chronic gamma irradiation. Kasetsart J. Nat. Sci. 2012;46:383-393.
13. Mutlu SS, Djapo H, Ozmen SF, Selim C, Tuncel N. Gamma-ray irradiation induces useful morphological variation in Bermuda grass. Not. Bot. Horti Agrobo. 2015;43(2):515-520.
14. Krishna G, Shivashankar G, Nath J. Mutagenic response of Rhodes grass (Chloris gayana Kunth.) to gamma rays. Environ. Exp. Bot. 1984;24(2):197-205.
15. Zaka R, Vandecasteele CM, Misset MT. Effect of low chronic doses of ionizing radiation on antioxidant enzymes and G6PDH activities in Stipa capillata (Poaceae). J. Exp. Bot. 2002;53:19791987.
16. Lal RK, Neelakshi S, Sharma JR, Mishra HO, Nidhi S. Radiationinduced changes in Java citronella (Cymbopogon winterianus). J. Med. Aromat. Plant Sci. 2000;22(1B):474-478.
17. Kainthura P, Srivastava R. Induction of genetic variability and isolation of mutants in tuberose (Polianthes tuberosa L.). Trop. Agric. Res. 2015;26(4):721-732.
18. Pandey RK, Bhat DJ, Sheetal D, Arvinder S, Nomita L, Shivani J. Evaluation of gladiolus cultivars under subtropical conditions of Jammu. Int. J. Agric. Sci. 2012;8(2):518-522.
19. Safeena SA, Thangam M. Field performance of gladiolus cultivars for growth, yield and quality cut flower production under humid agro-climatic conditions of Goa. Int. J. Agric. Sci. 2019;11(3):7797-7800.
20. Reiter WD, Chapple CCS, Somerville CR. Altered growth and cell walls in a fructose-deficient mutant of Arabidopsis. Science. 1993;261:1032-1035.
21. Takahashi T, Gasch A, Nishizawa N, Chua NH. The DIMINUTO gene of Arabidopsis is involved in regulating cell elongation. Genes Dev. 1995;9:97-107.
22. Lal RK, Sharma JR, Mishra HO. Effects of gamma radiation on economic traits in Java citronella (Cymbopogon winterianus). J. Med. Aromat. Plant Sci. 1998;20:717-721.
23. Lal M, Dutta S, Munda S, Pandey SK. Identification and registration of a high essential oil yielding variety (Jor Lab L-14) of lemongrass (Cymbopogon flexuosus L.) through mutation breeding technique. J. Essent. Oil-Bear. Plants. 2018;21(6):1604-1611.
24. Fowler DB, MacQueen KF. Effect of low doses of gamma radiation on yield and other agronomic characters of spring wheat (Triticum aestivum). Radiat. Bot. 1972;12(5):349-353.
25. Vinutha M, Naik KT, Pavan R, Shivakameshwari MN, Saraswathi KJT. Essential oil studies and RAPD markers in sUV-B treated Cymbopogon flexuosus (Nees ex Steud.) Wats. Int. J. Biosci. 2014;4(1):367-371.
26. Maffei M, Scannerini S. UV-B effect on photomorphogenesis and essential oil composition in peppermint (Mentha piperita L.). J. Essent. Oil Res. 2000;12:523-529.
27. Nitz GM, Schnitzler WH. Effect of PAR and UV-B radiation on the quality and quantity of the essential oil in sweet basil (Ocimum basilicum L.). Acta Hortic. 2004;659:375-381.
28. Karousou R, Grammatikopoulos G, Lanaras T, Manetas Y, Kokkini S. Effects of enhanced UV-B radiation on Mentha spicata essential oils. Phytochemistry. 1998;49:2273-2277.
29. How to cite this article: Patidar D, Meena K, Kumar R, Rawat R, Shukla S, Sherawat S. Harnessing gamma radiation-induced mutagenesis for enhanced essential oil yield and morphological improvement in lemongrass (Cymbopogon flexuosus Nees ex Steud). International Journal of Research in Agronomy. 2026;9(9):1377-1381. doi: https://www.doi.org/10.33545/261806 0X.2026.v9.i9s.6704