Gamma Rays Limit Root Growth but Cause Leaf Patterns in Salvia Plants

Greg Howard
25th January, 2024

Gamma Rays Limit Root Growth but Cause Leaf Patterns in Salvia Plants

Bog sage (Salvia uliginosa)

Photo adapted from: Leonel Roget / CC BY (Source)
Ornamental shrubs are popular in landscaping, valued for their aesthetic appeal and ability to attract pollinators. However, the range of commercially available varieties within a species can be limited. Plant breeders use various techniques to increase this variation, and one such method is mutation breeding – intentionally inducing genetic changes to create new traits. A challenge with this technique is that it can often negatively impact plant health and growth. Researchers at the University of Georgia[1] recently investigated how to optimize mutation breeding in Salvia uliginosa, a shrub known for its blue flowers and pollinator-attracting qualities. The study focused on using gamma radiation to induce mutations. Gamma radiation is a form of energy that can alter the plant’s DNA, leading to new characteristics. The initial aim was to determine the optimal dose of gamma radiation that would induce mutations without severely harming the plants. Cuttings – sections of stem used to grow new plants – were exposed to varying doses of radiation: 0, 10, 20, 30, 40, or 50 Gray (Gy). Gray is a unit measuring the absorbed dose of radiation. The researchers then assessed how these different doses affected rooting success, survival rate, and plant height. The results showed that higher doses of radiation generally had negative effects. Root quality, the percentage of cuttings that successfully developed roots, and plant height decreased as the radiation dose increased. However, a second set of cuttings, referred to as M1V2 selections, showed that rooting ability wasn’t impacted. This suggests that some plants may be more resilient to the damaging effects of radiation. Following these initial findings, a second experiment was conducted, treating 25 cuttings with 35 Gy of gamma radiation, aiming to induce beneficial mutations. This second experiment yielded a promising result: one mutant plant with variegated leaves – leaves displaying multiple colors – was identified, representing a mutation rate of 4%. This demonstrates that a dose of 35 Gy could successfully induce visible mutations. The success of inducing mutations in Salvia uliginosa using gamma radiation aligns with similar work done in other ornamental plants. For example, researchers have successfully used gamma radiation to create new flower colors and forms in chrysanthemums[2], and to enhance desirable traits like 6-gingerol content in ginger[3]. These studies highlight the potential of gamma radiation as a tool for improving ornamental species. The findings from the University of Georgia study are significant because they identified a radiation dose (35 Gy) that balances the need to induce mutations with the need to maintain plant health. This is crucial because excessive radiation can lead to undesirable effects, such as reduced growth or even plant death. The observed mutation rate of 4% is also encouraging, suggesting that the treatment is effective in generating genetic variation. Interestingly, the negative effects of radiation on rooting observed in the initial experiment, but not in the M1V2 selections, suggest that plants can exhibit varying levels of sensitivity to radiation. This phenomenon is not fully understood, but it could be related to differences in DNA repair mechanisms or other protective factors within the plants. The ability to select for radiation-tolerant plants, as potentially demonstrated by the M1V2 selections, could further improve the efficiency of mutation breeding. Furthermore, the use of gamma radiation in plant breeding has also been shown to alter volatile compound compositions in roses[4], demonstrating that radiation-induced mutations can affect a wide range of plant characteristics beyond just visible traits like flower color or leaf variegation. This suggests that mutation breeding could be used to improve other desirable qualities in Salvia uliginosa, such as fragrance or disease resistance.

BiotechGeneticsPlant Science

References

Main Study

1) Co60 gamma irradiation reduces rooting ability in M1V1Salvia uliginosa while inducing leaf variegation.

Published 24th January, 2024

https://doi.org/10.1080/09553002.2024.2304852

Related Studies

2) Induction of novel inflorescence traits in Chrysanthemum through 60Co gamma irradiation.

https://doi.org/10.1080/09553002.2020.1793023

3) Improvement of 6-gingerol production in ginger rhizomes (Zingiber officinale Roscoe) plants by mutation breeding using gamma irradiation.

https://doi.org/10.1016/j.apradiso.2020.109193

4) Comparative Analysis of Volatile Compounds of Gamma-Irradiated Mutants of Rose (Rosa hybrida).

https://doi.org/10.3390/plants9091221


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