The Role of Dark Septate Endophytic Fungal Isolates in the Accumulation of Cesium by Chinese Cabbage and Tomato Plants under Contaminated Environments

Abstract

Following the 2011 Fukushima Daiichi Nuclear Power Plant accident, the preservation of the food chain from radionuclides contamination has become of crucial importance. The potential of Dark septate endophytic fungi in the management of Cs accumulation in plants under contaminated environments was investigated using Chinese cabbage and tomato plants. Four endophytic fungal isolates of different species, i.e. Pseudosigmoidea ibarakiensis I.4-2-1, Veronaeopsis simplex Y34, Helminthosporium velutinum 41-1, and as yet unidentified taxon 312-6 were tested In Vitro in two levels of Cs (5ppm and 10ppm). On the plant growth, the inoculation of the selected DSEs to both Chinese cabbage and tomato resulted in an increased biomass of up to 82% and 122%, respectively compared to control (non-inoculated) plants. With regards to the Cs accumulation, it varied with the host plant considered. In Chinese cabbage, DSEs inoculation caused higher Cs accumulation in above ground plant parts, whereas in tomato, Cs accumulation decreased significantly with three of the isolates tested, i.e., V. simplex Y34, P. ibarakiensis I.4-2-1, and the as yet unidentified taxon 312-6 suggesting low-risk transfer on the above ground plants parts as a result of high and negative plant reactions rather than high and positive reactions as it is the case with Chinese cabbage. These results suggested that DSEs can be recommended for use with Chinese cabbage to enhance phytoremediation of Cs in surrounding contaminated areas. With tomato, DSEs can be recommended for decreasing the accumulation of Cs in plants under contaminated environments.

Unraveling the role of dark septate endophyte (DSE) colonizing maize (Zea mays) under cadmium stress: physiological, cytological and genic aspects

“…This suggests that E. pisciphila , found colonizing numerous plant roots in an ancient Pb-/Zn- Slag heap in China 21 and previously reported as a fish-pathogenic fungus 22 23 , confers a marked cadmium tolerance to its host plant and plays a functional role as a beneficial plant-associated fungus with DSE morphological characteristics. The reduced Cd accumulation in both shoots and roots of DSE-inoculated maize suggests that plants which accumulate and/or tolerate Cd have evolved an alternative mechanism, utilizing DSE colonization, to resist taking up metals in the soil and/or to tolerate metals inside cells 14 19 .…”

“…For example, field surveys from Ban, et al 18 showed that DSE colonization was negatively correlated with the translocation of Pb (r = −0.88, p < 0.05) accumulated in six dominant plant species grown on Qiandongshan Pb-Zn mine tailings, China. To evaluate the role of DSEs in phytoremediation of radioactive cesium (Cs), Diene, et al 19 identified the distinct responses of DSE-inoculation on Cs accumulation in two commercial crops; they observed that DSEs significantly decreased Cs accumulation in DSE-inoculated tomato but enhanced phytoremediation of Cs by Chinese cabbage, while also significantly increasing the biomass of both crops by up to 82 and 122% (for Chinese cabbage and tomato, respectively), compared to non-inoculated controls. Also, data from Likar and Regvar 14 revealed that DSEs isolated from Salix caprea reduced metal uptake and improved the general physiology of their host plants via various effects, such as increasing chlorophyll concentrations and transpiration rates, for example.…”

A novel role for methyl cysteinate, a cysteine derivative, in cesium accumulation in Arabidopsis thaliana

“…Various factors have been investigated and suggested as positive regulators of cesium accumulation in plants. For example, inoculation with root-associated microorganisms has been shown to improve cesium accumulation in plants 13 14 15 16 . Some researchers have reported that an arbuscular mycorrhizal (AM) fungi improve cesium phytoaccumulation efficiency 17 18 , while others have contradicted this 19 20 , and there is an ongoing debate on the effect of cesium on colonisation of AM fungi 21 .…”

Endorhizal Fungal Association and Colonization Patterns in Solanaceae

“…Solanaceous plants have a high affinity for DSE fungi. The highest number of DSE fungal isolates have frequently been obtained from roots of solanaceous plants (Diene et al 2014). For example, Narisawa et al (2007) showed that eggplant was a particularly effective species for baiting the DSE fungus Heteroconium chaetospira from the soil.…”