Anther‐smut fungi from more contaminated sites in Chernobyl show lower infection ability and lower viability following experimental irradiation

• Published in: Ecology and evolution Vol. 10; no. 13; pp. 6409 - 6420
• Main Authors: Arnaise, Sylvie, Shykoff, Jacqui A., Møller, Anders P., Mousseau, Timothy A., Giraud, Tatiana
• Format: Journal Article
• Language: English
• Published: England John Wiley & Sons, Inc 01-07-2020; Wiley Open Access; John Wiley and Sons Inc; Wiley
• Subjects: Anthers; Biodiversity; Birds; Budding; Contamination; Damage tolerance; Deoxyribonucleic acid; Developmental stages; Disasters; disease; DNA; DNA damage; Experiments; Exposure; Fertility; Fitness; Fungi; Genomes; High resistance; Host plants; infection; Infections; Ionizing radiation; Irradiation; Karyotypes; Life cycle assessment; Life cycles; Life Sciences; Man made disasters; Meiosis; Microbotryum lychnidis‐dioicae; Mutation; Nuclear accidents & safety; Original Research; pathogen; Populations and Evolution; radiation; Radiation damage; Radiation measurement; Radiation tolerance; Radioactive contamination; Radioactive pollution; Radioactivity; resistance; Seeds; Signs and symptoms; Silene latifolia; Smut; Spores; Strains (organisms); tolerance; Viability; γ Radiation; infection; disease; Microbotryum lychnidis‐dioicae; fungi; radiation; pathogen; Silene latifolia; resistance; tolerance; radioactivity; Microbotryum lychnidis-dioicae
• ISSN: 2045-7758; 2045-7758
• DOI: 10.1002/ece3.6376

The long‐term contamination that followed the nuclear disaster at Chernobyl provides a case study for the effects of chronic ionizing radiation on living organisms and on their ability to tolerate or evolve resistance to such radiation. Previously, we studied the fertility and viability of early developmental stages of a castrating plant pathogen, the anther‐smut fungus Microbotryum lychnidis‐dioicae, isolated from field sites varying over 700‐fold in degree of radioactive contamination. Neither the budding rate of haploid spores following meiosis nor the karyotype structure varied with increasing radiation levels at sampling sites. Here, we assessed the ability of the same M. lychnidis‐dioicae strains to perform their whole life cycle, up to the production of symptoms in the plants, that is, the development of anthers full of fungal spores; we also assessed their viability under experimental radiation. Fungal strains from more contaminated sites had no lower spore numbers in anthers or viability, but infected host plants less well, indicating lower overall fitness due to radioactivity exposure. These findings improve our understanding of the previous field data, in which the anther‐smut disease prevalence on Silene latifolia plants caused by M. lychnidis‐dioicae was lower at more contaminated sites. Although the fungus showed relatively high resistance to experimental radiation, we found no evidence that increased resistance to radiation has evolved in populations from contaminated sites. Fungal strains from more contaminated sites even tolerated or repaired damage from a brief acute exposure to γ radiation less well than those from non‐ or less contaminated sites. Our results more generally concur with previous studies in showing that the fitness of living organisms is affected by radiation after nuclear disasters, but that they do not rapidly evolve higher tolerance.
Strains of the anther‐smut castrating fungus from more contaminated sites in Chernobyl infected host plants less well, indicating lower fitness due to radioactivity exposure. The fungus showed relatively high resistance to experimental radiation, but we found no evidence that resistance to radiation has evolved within these populations following radiation experiments. Strains from sites with higher field radiation had in contrast lower tolerance to experimental acute radiation.