60Co Irradiation Influences Germination and Phenotype of Three Pavonia Species

Abstract

The genus Pavonia is one of the largest genera in the Malvaceae species; it is mainly distributed in South America. Three species of Pavonia were identified based on different flower colors and potential for landscape use in the southeastern United States. These species produce a large amount of seed at the end of the blooming season, which is not ideal for ornamental use. To reduce the seed set, gamma irradiation was used for mutation induction and propensity to induce compactness and sterility. A preliminary study indicated that the seed of Pavonia hastata would germinate at irradiation rates up to 2000 Gy. Seeds of three species were treated with six different dose rates ranging from 0 Gy to 1000 Gy to determine the ideal rate for Pavonia breeding and how gamma irradiation affected seed germination. M1 (the first mutant generation) P. lasiopetala and P. missionum were sown in 2018 and planted in the field at the University of Georgia Durham Horticulture Farm on 1 May 2019, as were M2 (the second mutant generation) seeds of P. hastata. Seed germination in 2019 showed no significance due to treatment but significance due to species and species by treatment interaction. Field evaluation performed in 2019 indicated that height was not influenced by irradiation for any of the three species but that the width index was. Flower diameter and leaf area of P. missionum became smaller as the irradiation rate increased, but the other two species showed no trends. Chlorophyll mutations were observed on P. hastata at the 1500 Gy level, which has attractive traits for ornamental use.

Biological effects of gamma-ray radiation on tulip (Tulipa gesneriana L.)

“…These findings positively agree with germination percentage studies in Cicer arietinum L. ( Mullainathan, 2016 ), Abelmoschus esculentus L. Moench ( Asare et al, 2017 ), Sophora davidii Franch. ( Wang et al, 2017 ), and Pavonia hastata ( Yue & Ruter, 2020 ). This reduction in seed germination might be due to the effect of mutagens on meristematic tissues of the seed as well as chromosomal aberrations and interruptions in DNA replication and growth regulators ( Wang et al, 2017 ; Asare et al, 2017 ).…”

“…Numerous researchers have reported that gamma rays affect the morphology of treated plants ( Yue & Ruter, 2020 ; Li et al, 2021 ; Asare et al, 2017 ). Indeed, this study also found that plant height and flowering rate decreased significantly ( P < 0.05) with increasing doses of γ-ray irradiation.…”

“…It has been observed that gamma-ray irradiation in chrysanthemum ( Dendranthema grandiflorum ) significantly inhibits plant germination and growth, and changing flower colour ( Kim et al, 2016 ). Recently, Yue & Ruter (2020) also experimentally confirmed that gamma-ray irradiation is effective in inducing genomic variations in three Pavonia species, resulting in the changes of germination percentage, flower size, leaf area, leaf chlorophyll, and plant height.…”

“… Fan et al (2014) reported that γ-irradiation induced a substantial increase in malondialdehyde (MDA) content, but reduced the total chlorophyll content in Zizania latifolia plants, suggesting a potential mechanism of plant growth inhibition under irradiation stress. In addition, it has been demonstrated that DNA fragmentation and cell death may inhibiter plant growth and development ( Yamaguchi, 2018 ; Yue & Ruter, 2020 ). Yamaguchi et al (2008) found that gamma-ray irradiation, even with low doses (15 Gy), reduced the nuclear DNA content in chrysanthemum, suggesting that irradiation efficiently induced mutations in the plants.…”

Mutagenic Effect of 60Co γ-Irradiation on Rosa multiflora ‘Libellula’ and the Mechanism Underlying the Associated Leaf Changes

“…Using 60 Co-γ-rays irradiation to breed roses has the characteristics of a simple experimental method, breaking gene linkage, short breeding years, obtaining mutants in a short time, and selecting new varieties efficiently. Gamma rays can cause various morphological and physiological changes in plants through direct and indirect interactions with organisms, such as abnormal appearance, reduced growth, and reduced reproductive capacity [ 34 ]. It also can cause physiological changes such as accumulation of anthocyanins [ 35 ], expansion of root cells [ 36 ], changes in photosynthesis [ 37 ], dysregulation of antioxidant systems, etc.…”