Effects of fungal seed endophyte FXZ2 on Dysphania ambrosioides Zn/Cd tolerance and accumulation.

Metal-induced oxidative stress in contaminated soils affects plant growth. In the present study, we evaluated the role of seed endophyte FXZ2 on Dysphania ambrosioides Zn/Cd tolerance and accumulation. A series of pot experiments were conducted under variable Zn (500, 1,000, and 1,500 mg kg-1) and Cd (5, 15, 30, and 60 mg kg-1). The results demonstrated that FXZ2-inoculation significantly enhanced the growth of D. ambrosioides and improved its chlorophyll and GSH content. In the rhizosphere, FXZ2 inoculation changed the chemical speciation of Zn/Cd and thus affected their uptake and accumulation in host plants. The exchangeable and carbonate-bound fractions (F1 + F2) of Zn decreased in the rhizosphere of FXZ2-inoculated plants (E+) as compared to non-inoculated plants (E-) under Zn stress (500 and 1,000 mg kg-1), correspondingly, Zn in the shoots of E+ decreased (p < 0.05). However, at Cd stress (30 and 60 mg kg-1), the F1 + F2 fractions of Cd in E+ rhizospheric soils increased; subsequently, Cd in the shoots of E+ increased (p < 0.05). FXZ2 could exogenously secrete phytohormones IAA, GA, and JA. The study suggests that seed endophyte FXZ2 can increase Zn/Cd tolerance of host plant by altering Zn/Cd speciation in rhizospheric soils, as well as exogenous production of phytohormones to promote growth, lowering oxidative damage while enhancing antioxidant properties. For Zn/Cd accumulation, it has opposite effects: Zn uptake in E+ plants was significantly (p < 0.05) decreased, while Cd accumulation in E+ plants was significantly (p < 0.05) increased. Thus, FXZ2 has excellent application prospects in Cd phytoextraction and decreasing Zn toxicity in agriculturally important crops.

Seasonal variation of potentially toxic metal contamination in Yamuna riverine ecosystem, Delhi, India.

The River Yamuna in Delhi region, the National Capital Territory (NCT) of India, carries potentially toxic metals such as Cr, Pb, Mn, Mg, Hg, Fe and Zn. These contaminants are discharged mainly from industrial wastes, agricultural and household activities and domestic sewage. A total of 12 stations (2.5 to 3.5 km apart from each other) were selected for the study, covering the upstream and downstream areas of river Yamuna in Delhi. The investigated sites were evaluated for significant difference between upstream and downstream locations of river Yamuna in three different time periods (June, October, February). Metal contamination were measured in water, sediments (2 µm) and nearby agriculture soil of the river Yamuna, and found with high metal loads as compared with the international standards, chiefly in the downstream sites as the river flows through the Delhi stretch. The multivariate statistical analysis revealed spatial and temporal variations in the metal concentrations which suggest seasonal variation and common point source of some metals while different sources of other metals. The contamination of the river water and adjoining agriculture soils points towards possible entry of these metals into the food chain. The study indicates that considering the current status of metal pollution, the surface water is not in good conditions for use as drinking purpose because of the high concentrations of few potentially toxic metals. Our study recommends regular monitoring of toxic metals in Yamuna river water and sediments, strict ban on the domestic, agriculture and industrial waste disposal for the restoration of the river to its natural state.

Fungal Seed Endophyte FZT214 Improves Dysphania ambrosioides Cd Tolerance Throughout Different Developmental Stages.

Phytoremediation is a promising remediation method of heavy metal (HM)-contaminated soils. However, lower HM tolerance of metal accumulator inhibits its practical application and effects. The current study was aimed to illustrate the role of fungal seed endophyte (FZT214) in improving Dysphania ambrosioides Cd tolerance during different developmental stages under various Cd stresses (5, 15, 30 mg kg-1) by pot experiments. The results showed that FZT214 significantly (p < 0.05) improved the host plant's growth at the flowering and fruiting stage in most of the treatment, while at the growing stage the increase was less (p > 0.05). The seed yield was also improved (p < 0.05) in the FZT214-inoculated plants (E+) and induced early flowering was observed. Moreover, the inoculation also positively affected total chlorophyll content, antioxidant process, and lipid peroxidation in most of the treatments throughout three developmental stages. Not all but in most cases, IAA and GA were more in E+ plants while JA was more in the E- plants (non-inoculated plants) during three developmental stages. The results suggested that the colonization of FZT214 to the D. ambrosioides might trigger multiple and comprehensive protective strategies against Cd stress, which mainly include activation of the dilution effects, induced biochemical changes to overcome damage from Cd toxicity, and alteration of the endogenous phytohormones. FZT214 can find competent application in the future to improve the growth of other crop plants.

Fungal Endophytic Communities of Two Wild Rosa Varieties With Different Powdery Mildew Susceptibilities.

Powdery mildew (PM) is one of the most devastating and wide spread fungal diseases of rose, which seriously decrease its productivity and commercial value. In the present study, the endophytic fungal communities of two wild Rosa varieties (Rosa multiflora Thunb and R. multiflora var. carnea Redouté and Thory) with different PM susceptibilities were studied through Illumina MiSeq sequencer. A total of 14,000,424 raw reads were obtained from 60 samples, and 6,862,953 tags were produced after merging paired-end reads. 4462 distinct OTUs were generated at a 97% similarity level. It was found that only 34.2% of OTUs shared between two plant varieties. All of the OTUs were assigned into four fungal phyla, 17 classes, 43 orders, 86 families, 157 genera, and 208 species. Members of Ascomycota were found to be the most common fungal endophytes (EF) among all plant samples (93.7% relative abundance), followed by Basidiomycota (4.7% relative abundance), while Zygomycota and Glomeromycota were found to be rare and incidental. At each developmental stage of plants, the diversity and community structure of EF between two Rosa varieties showed significant differences. Both PCoA plots and PERMANOVA analyses indicated that developmental stage was the major factor contributing to the difference between the Rosa varieties (R 2 = 0.348, p < 0.001). In addition, plant varieties and tissues were also important factors contributing to the difference (R 2 = 0.031, p < 0.05; R 2 = 0.029, p < 0.05). Moreover, Neofusicoccum, Rhodosporidium, and Podosphaera, etc., were found to be significantly different between two Rosa varieties, and some of the endophytes may play a role in PM resistance. These finding are encouraging to testify the potential use of these fungi in the biocontrol of PM in future studies.

Endophytic fungal community of Dysphania ambrosioides from two heavy metal-contaminated sites: evaluated by culture-dependent and culture-independent approaches.

Endophytic fungal communities of Dysphania ambrosioides, a hyperaccumulator growing at two Pb-Zn-contaminated sites, were investigated through culture-dependent and culture-independent approaches. A total of 237 culturable endophytic fungi (EF) were isolated from 368 tissue (shoot and roots) segments, and the colonization rate (CR) ranged from 9.64% to 65.98%. The isolates were identified to 43 taxa based on morphological characteristics and rDNA ITS sequence analysis. Among them, 13 taxa (30.23%) were common in plant tissues from both sites; however, dominant EF were dissimilar. In culture-dependent study, 1989 OTUs were obtained through Illumina Miseq sequencing, and dominant EF were almost same in plant tissues from both sites. However, some culturable EF were not observed in total endophytic communities. We suggest that combination of both culture-dependent and culture-independent methods will provide more chances for the precise estimation of endophytic fungal community than using either of them. The tissue had more influence on the culturable fungal community structure, whereas the location had more influence on the total fungal community structure (including culturable and unculturable). Both culture-dependent and culture-independent studies illustrated that endophytic fungal communities of D. ambrosioides varied across the sites, which suggested that HM concentration of the soil may have some influence on endophytic fungal diversity.