Xingxu Zhang

Effects of cadmium stress on seed germination and seedling growth of Elymus dahuricus infected with the Neotyphodium endophyte

Various cadmium (Cd) concentrations (0, 50, 100, 200 and 300 μmol L−1) affected Elymus dahuricus seed germination, seedling growth, antioxidative enzymes activities (AEA), and amounts of malondialdehyde (MDA) and proline present. These influences were determined for separate E. dahuricus cohorts known to be either infected (E+) or non-infected (E−) by a Neotyphodium endophyte. Under high Cd concentrations (100, 200 and 300 μmol L−1), E+ specimens showed a significantly (P<0.05) higher germination rate and index, as well as higher values for shoot length, root length and dry biomass. However, the germination rate and index, root length and dry weight did not show a significant (P<0.05) difference under the low Cd concentrations (0 and 50 μmol L−1). AEA and proline content increased, as did MDA content, in the E+ (vs. E−) specimens under high Cd concentrations. There was no significant (P>0.05) difference under low Cd concentrations. Endophyte infection was concluded to be of benefit to E. dahuricus exposed to high Cd concentrations.

Effects of cutting frequency and height on alkaloid production in endophyte-infected drunken horse grass (Achnatherum inebrians)

An evaluation was performed on the influence of mowing height (2.5, 5.0 or 7.5 cm) and mowing frequency (weekly or fortnightly) on levels of ergot alkaloids (ergine and ergonovine) formed in drunken horse grass, Achnatherum inebrians, grown under greenhouse conditions. Samples were taken monthly and alkaloids were extracted and analyzed by reverse-phase HPLC. Alkaloid levels increased more or less linearly with plant age over the first four months following establishment. Levels were higher in samples cut fortnightly compared to those cut weekly, and were higher when plants were cut at a mowing height of 7.5 cm vs. 2.5 cm. In most cases, the highest alkaloid levels observed were almost three times those of the lowest. If plant protection applications are developed for the endophytic fungus, Neotyphodium gansuense, it will be necessary to be aware of the potential role of plant husbandry practices (e.g., defoliation frequency and intensity) for reducing or enhancing levels of plant alkaloids. Similar husbandry factors may affect alkaloid levels in other Neotyphodium-grass associations, which would be interesting for further study.

Cytotoxic effect of ergot alkaloids in Achnatherum inebrians infected by the Neotyphodium gansuense endophyte.

Ergonovine or ergonovinine was isolated from the aerial parts of endophyte (Neotyphodium gansuense) infected (E+) drunken horse grass (Achnatherum inebrians), neither of which existed in endophyte-free (E-) plants. Both of these ergot alkaloids had a cytotoxic effect on animal smooth muscle cells and increased cell growth inhibition with greater concentrations, in a significantly (P < 0.05) positive correlation. The median inhibitory concentrations (IC50) for ergonovine and ergonovinine were 71.95 and 72.75 μg/mL, respectively. These results indicate that endophytic ergot alkaloids may be the cause of drunken horse grass poisoning.

Antifungal activity and phytochemical investigation of the asexual endophyte of Epichloë sp. from Festuca sinensis

Much research is now being conducted on grasses-Epichloe associations. The asexual Epichloe species have attracted much attention over the past 30 years as they can provide benefits to important forage grasses, in particular perennial ryegrass (Lolium perenne), annual ryegrass (L. multiflorum), tall fescue (Festuca arundinacea), and meadow fescue (F. pratense). Some findings suggest that grasses with an epichloe endophyte (E+) are more resistant to pathogenic fungi than uninfected (E–) grass. Tests using detached and attached leaves have shown that the size of lesions caused by pathogenic fungi are smaller on E+ leaves than on E– leaves. Products inhibitory to plant pathogenic fungi are produced by epichloe endophytes growing saprotrophically.

Effects of symbiotic Epichloë gansuensis endophyte on drunken horse grass (Achnatherum inebrians) growth and seed production

The effects of the fungal endophyte Epichloë gansuensis on drunken horse grass (Achnatherum inebrians) were determined over a 4-year period in a field growth experiment near Lanzhou, Gansu, China. Endophyte-infected (E+) A. inebrians vs non-infected (E−) control plants were compared for height, tiller number, weight of above-ground biomass, seed production and plant survival. Plant parameters were observed to be significantly higher (P < 0.05) for E+ specimens (vs E− plants) on most occasions. Growth parameters, seed yield and plant survival decreased significantly (P < 0.05) over time, while the differences between E+ and E− plants increased over the duration of the investigation. Endophyte infection was concluded to be of benefit to the growth, seed yield and plant survival of A. inebrians under conditions in the field.

Does dormancy protect seeds against attack by the pathogenic fungus Fusarium tricinctum in a semiarid grassland of Northwest China

AimsSoil fungal pathogens can result in the failure of seedling establishment, but the effects of fungicide applications on seed/seedling survival have differed among studies. We assumed that the variation may relate to seed dormancy/germination characteristics and hypothesized that nondormant germinating seeds are more likely to be killed by fungal pathogens than dormant seeds.MethodsDormant and nondormant seeds of Stipa bungeana and Lespedeza davurica were inoculated with a pathogenic fungus Fusarium tricinctum under laboratory and field conditions. The outcomes of seed/seedling fate and other parameters were evaluated.ResultsIn the laboratory, nondormant seeds inoculated with F. tricinctum developed white tufts of mycelium on the radicles of germinating seeds causing them to quickly die, but dormant seeds remained intact. In contrast, in the field inoculation with F. tricinctum did not cause higher mortality of nondormant than dormant seeds but resulted in higher percentages of seedling death before they emerged from soil than the controls.ConclusionsOur results suggest that dormancy protects seeds from being attacked by some pathogens by preventing germination, but the protection is lost once germination has commenced. Further study involving various plant species with more seeds is needed to assess the generality of this pathogen-seed interaction hypothesis.

Chemical composition and antifungal activity of the volatile oil from Epichloë gansuensis, endophyte-infected and non-infected Achnatherum inebrians

Endophytic fungi that belong to the genus Epichloe (including species previously classified in the genus Neotyphodium) have been found in many cool-season grasses (subfamily Pooideae). Achnatherum inebrians (Hance) Keng (drunken horse grass, DHG) is a toxic perennial bunchgrass, distributed mainly throughout the harsh conditions of alpine or sub-alpine grasslands in the northwest of China. This species is usually infected by the fungal endophyte Epichloe gansuensis, which apparently enhances its resistance to the abiotic and biotic stress.

Antifungal activity of petroleum ether extracts from Achnatherum inebrians infected with Neotyphodium gansuense

(Hance) Keng (drunken horse grass, DHG) is a toxic perennial bunchgrass, which is so-named because it is associated with the narcosis of livestock which graze on native grasslands in the northwest of China [1]. DHG is distributed mainly throughout the harsh conditions of alpine or sub-alpine grasslands, and this species is usual-ly infected by the fungal endophyte

Interactive effects of water stress and powdery mildew ( Blumeria graminis ) on the alkaloid production of Achnatherum inebrians infected by Epichloë endophyte

Achnatherum inebrians, also known as drunken horse grass (DHG), is a toxic perennial bunch grass that can be infected by Epichloë gansuensis or E. inebrians (Chen et al., 2015). It is well known that Epichloë fungal endophytes can protect their host plants from herbivores by producing different classes of alkaloids. A recent trial demonstrated that sheep exhibited notable toxicity symptoms by directly feeding with endophyte-infected (E+) A. inebrians (Liang et al., 2017). The changes in the alkaloid contents of host plants may be closely related to the tolerance of DHG to the changes in environmental temperature, soil pH, heavy metal composition (Wan, 2017) as well as salt and drought stresses (Zhang et al., 2011). In addition, the presence of Epichloë endophyte has been reported to result in significant improvements in the resistance of host DHG to powdery mildew under various soil water conditions (Xia et al., 2016). However, it is still unclear whether the changes in the alkaloid contents of host DHG would affect the disease resistance. Therefore, this study was conducted to determine whether the damage caused due to powdery mildew affects the symbionts’ alkaloid production of DHG under different soil moisture conditions, which could further strengthen our understanding on whether the alkaloid types and contents play a role in the process of host DHG disease resistance. On April 24, 2016, the full grain and healthy Epichloë endophyte-infected seeds were selected and planted into 80 plastic pots (diameter: 24 cm, height: 15 cm), with three seeds per pot that was filled with vermiculite (200 g) and had been sterilized earlier in an oven at 120°C for 5 h. On June 15, the pots were maintained in a constant-temperature greenhouse (temperature: 26°C±2°C) for 7 weeks, after which a slight powdery mildew was observed in the plants. A total of 64 pots containing similar sized seedlings were selected for the present experiment. The selected plants were cut at 15 cm above the vermiculite surface to ensure that the height of all plants was equal prior to imposing the trial condition. Meanwhile, the water-holding capacity of each selected pot was reduced to 15% relative saturation moisture content (RSMC). Then, the strong drought (15% RSMC), light drought (30% RSMC), normal moisture (45% RSMC), and abundant moisture (60% RSMC) soil water conditions were established. The E+ seedlings were assigned to 16 pots for each soil water condition, eight experimental replicates

Effect of Epichloë gansuensis Endophyte on the Nitrogen Metabolism, Nitrogen Use Efficiency, and Stoichiometry of Achnatherum inebrians under Nitrogen Limitation

The systemic fungal endophyte of the grass Achnatherum inebrians, Epichloë gansuensis, has important roles in enhancing resistance to biotic and abiotic stresses. In this work, we first evaluated the effects of E. gansuensis on nitrogen metabolism, nitrogen use efficiency, and stoichiometry of A. inebrians under varying nitrogen concentrations. The results demonstrated that E. gansuensis significantly improved the growth of A. inebrians under low nitrogen conditions. The fresh and dry weights, nitrogen reductase, nitrite reductase, and glutamine synthetase activity, NO3-, NH4+, N, and P content, and also the total N accumulation, N utilization efficiency, and N uptake efficiency were all higher in leaves of A. inebrians with E. ganusensis (E+) plants than A. inebrians plants without this endophyte (E-) under low nitrogen availability. In conclusion, E. gansuensis has positive effects on improving the growth of A. inebrians under low-nitrogen conditions by modulating the enzymes of nitrogen metabolism and enhancing nitrogen use efficiency.