Department of Horticultural Science, College of Agriculture, Isfahan University of Technology, 84156-83111, Isfahan, Iran.
Department of Horticultural Science, College of Agriculture, Isfahan University of Technology, 84156-83111, Isfahan, Iran.
Ecotoxicol Environ Saf. 2019 Oct 30;182:109412. doi: 10.1016/j.ecoenv.2019.109412. Epub 2019 Jul 8.
Perennial plants and their associated microorganisms grow in the areas that may be contaminated with long-lived gamma-emitting radionuclides. This will induce gamma stress response in plants and their accompanying microorganisms. The present work investigated the growth and physiological responses of Epichloe endophyte infected tall fescue to gamma radiation, as well as whether the endophyte could persist and infect the host plant once exposed to gamma radiation. Seeds of Iranian native genotype of 75B of tall fescue were exposed to different doses, including 5.0, 10.0, 15.0, 20.0, 30.0 and 40.0 krad of gamma ray from a Co source. Irradiated and unirradiated seeds were sown in pots and grown under controlled conditions in the greenhouse. The growth and physiological parameters associated with plant tolerance to oxidative stress of host plants, as well as endophytic infection frequency (% of plants infected) and intensity (mean number of endophytic hyphae per the field of view), were examined in 3 months-old seedlings. The results indicated that all gamma radiation doses (except 5.0 kr) significantly reduced the height and survival percentage of the host plant. Days to the emergence of seedling increased gradually as gamma doses rose. A dose-rate dependent induction was seen for photosynthetic pigments and proline content. Malondialdehyde (MDA) content grew with elevation of irradiation doses. Depending on the dose and time, the activities of antioxidant enzymes in the host plant responded differently to gamma radiation. Gamma radiation altered the enzyme activities with sever decline in SOD and CAT activities. However, it had barely any effect on in APX and POD activities. The results also revealed that the persistence and intensity of endophyte were affected after gamma-ray irradiation. The initial percentage of tall fescue seeds infected with the endophyte was 91% in un-irradiated seeds. Presence of the viable endophyte started to decline significantly (23%) at 5.0 kr of gamma radiation. A dramatic reduction in the presence and intensity of endophyte occurred at 10.0 to 40.0 kr intensities. Gamma radiation × trait (GT)-biplot analysis indicated positive correlations between the endophyte symbiosis and antioxidant enzyme activities. Also, negative correlations were observed between the endophyte and MDA content in the host plant. Our results suggest that radiation stress (doses over 5.0 kr) caused reduction in the growth and antioxidant enzyme activities of the host plant that accompanied by a dramatic reduction in the persistence and intensity of endophyte fungi. Our findings have provided the basic information for future studies on the effect of gamma irradiation on the interaction between endophytic fungi and its host plant.
多年生植物及其相关微生物生长在可能受到长寿命伽马放射性核素污染的区域。这将在植物及其伴随的微生物中诱导伽马应激反应。本研究调查了感染内生真菌的高羊茅对伽马辐射的生长和生理反应，以及内生真菌在暴露于伽马辐射后是否能够存活并感染宿主植物。来自伊朗 75B 原生基因型的高羊茅种子暴露于不同剂量的伽马射线，包括来自 Co 源的 5.0、10.0、15.0、20.0、30.0 和 40.0 krad。辐照和未辐照的种子被播种在盆中，并在温室中控制条件下生长。在 3 个月大的幼苗中，检查了与宿主植物对氧化应激的耐受性相关的生长和生理参数，以及内生真菌感染频率（感染植物的百分比）和强度（每个视野的内生菌丝平均数量）。结果表明，除 5.0 kr 外，所有伽马辐射剂量均显著降低了宿主植物的高度和存活率。随着伽马剂量的升高，幼苗出现的天数逐渐增加。观察到光合色素和脯氨酸含量的剂量依赖性诱导。丙二醛（MDA）含量随辐照剂量的升高而增加。根据剂量和时间的不同，宿主植物中抗氧化酶的活性对伽马辐射的反应也不同。伽马辐射改变了酶活性，SOD 和 CAT 活性严重下降。然而，它对 APX 和 POD 活性几乎没有影响。结果还表明，内生真菌的持久性和强度在伽马射线照射后受到影响。未经辐照的种子中内生真菌感染高羊茅种子的初始百分比为 91%。在 5.0 kr 的伽马辐射下，存活内生真菌的存在开始显著下降（23%）。在 10.0 至 40.0 kr 强度下，内生真菌的存在和强度急剧减少。伽马辐射×性状（GT）双标图分析表明，内生真菌共生与抗氧化酶活性之间存在正相关。此外，在宿主植物中也观察到内生菌与 MDA 含量之间存在负相关。我们的结果表明，辐射应激（剂量超过 5.0 kr）导致宿主植物生长和抗氧化酶活性降低，同时内生真菌的持久性和强度也大幅降低。我们的研究结果为进一步研究伽马辐照对内生真菌与其宿主植物相互作用的影响提供了基础信息。
