Next Article in Journal
Novel Insights for Metabiotics Production by Using Artisanal Probiotic Cultures
Next Article in Special Issue
Development of Plant–Fungal Endophyte Associations to Suppress Phoma Stem Canker in Brassica
Previous Article in Journal
3D Organoids: An Untapped Platform for Studying Host–Microbiome Interactions in Esophageal Cancers
Previous Article in Special Issue
Can Bacterial Endophytes Be Used as a Promising Bio-Inoculant for the Mitigation of Salinity Stress in Crop Plants?—A Global Meta-Analysis of the Last Decade (2011–2020)
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Microorganisms
Volume 9
Issue 11
10.3390/microorganisms9112183
microorganisms-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Interactive Effects of Epichloë Endophyte, Dormancy-Breaking Treatments and Geographic Origin on Seed Germination of Achnatherum inebrians

by
Yaqi Chen
1,
Kaiqi Su
2,
Chunjie Li
1,* and
James F. White
3
1
State Key Laboratory of Grassland Agro-Ecosystems, Key Laboratory of Grassland Livestock Industry Innovation, Ministry of Agriculture and Rural Affairs, Engineering Research Center of Grassland Industry, Ministry of Education, Gansu Tech Innovation Center of Western China Grassland Industry, Center for Grassland Microbiome, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou 730000, China
2
State Key Laboratory of Grassland Agro-Ecosystems, National Demonstration Center for Experimental Grassland Science Education, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou 730000, China
3
Department of Plant Biology, Rutgers University, New Brunswick, NJ 08901, USA
*
Author to whom correspondence should be addressed.
Microorganisms 2021, 9(11), 2183; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms9112183
Submission received: 8 September 2021 / Revised: 14 October 2021 / Accepted: 18 October 2021 / Published: 20 October 2021
(This article belongs to the Special Issue Microbial Endophytes: Functional Biology and Applications)
Browse Figures
Versions Notes

Abstract

:
Background: the cool-season grass Achnatherum inebrians (drunken horse grass) is an important species in the northwest grasslands of China. This grass engages in a symbiotic relationship with Epichloë endophytes, which affect host plants by increasing growth, repelling herbivores, and increasing tolerance to stressful environments. Methods: in this work, we evaluated the interaction effects of the endophyte on various dormancy-breaking treatments on A. inebrians seeds from six different locations. We used both endophyte-infected plants and noninfected plants and applied four dormancy-breaking methods to test germination. Results: our results showed that the germination rate of endophytic Achnatherum inebrians seeds from the Xiahe site (with highest altitude) was significantly higher than that from other sites when water soaking was applied (p < 0.05). Endophytic seeds had a greater germination rate, and soluble sugar, indole acetic acid (IAA), and gibberellin (GA) contents, under any condition. There was a significant interaction among the method, endophyte status, and origin regarding germination (p < 0.001); particularly, the effects of warm water soaking and endophyte infection on the germination of seeds from the Xiahe site was significant (p < 0.05). Conclusions: the infection of Epichloë endophyte is able to increase the content of soluble sugar, IAA, and GA, and stimulate the seed germination of A. inebrians.

1. Introduction

Seed dormancy prevents seeds from germinating, which protects plants from development in an unfavorable season [1]. Numerous studies proved that seed dormancy is caused by either seed coat hardness (physical) or embryo dormancy (physiological) [2,3]. Physical dormancy from seed drying causes the seed to remain dormant until sufficient water is available [4]. Physiological dormancy could be broken and achieved by removing the seed coat or surrounding tissues [5]. Another method to break dormancy is to add hormones, such as gibberellin (GA) and abscisic acid (ABA), which also promotes germination [2,6,7,8]. The seed is able to adjust the composition and deposition of both GA and ABA internally so that the seed remains dormant or germinates [9]. Studies suggest that ABA has a positive regulating effect on seed dormancy. Kucera [10] found that increased ABA content prevents germination, and internally produced ABA induces dormancy. A balance between GA and ABA is a critical factor controlling dormancy or germination [11]. In addition, Fennimore and Foley [12] suggested the prerequisites of dormancy termination are the breakdown of hormone balance, and GA plays a key role in seed germination. Indole acetic acid (IAA) as a growth regulator controls growth in the seed embryo [11]. Seed soluble sugar and starch substances provide essential nutrition for embryo development [13]. Soluble sugars in seeds are critical for embryo development [14]. Sugar is the main energy source for germination and further growth [15]. High concentrations of carbohydrate reduce chilling injury [16]. Germination is also influenced by the climate of geographic origin, in particular, mean annual temperature. Low elevation, warm climate, and rainfall promote seed germination. [16] found that Achnatherum inebrians from high altitudes with lower temperatures had higher germination rates than seed from warmer, low-elevation arid grasslands. Endophyte presence in seeds also affects the growth of plants and seed germination [17].
Drunken horse grass (Achnatherum inebrians) is one of the perennial toxic grasses in the northwest grassland of China [18,19]. Due to the presence of alkaloids produced by an endophytic fungus, livestock may be poisoned [20]. The study of drunken horse grass symbiosis began when Bruehl [21] isolated the fungus. Nan and Li [22] found two species and named them Epichloë gansuensis and Epichloë inebrians. The fungal endophyte is an example of an association between the plant and fungus that results in a positive outcome [23]. One feature of this endophyte is its intercellular growth inside plant tissues where it has a stable environment and essential nutrients [24]. Previous studies showed that infection by Epichloë species promoted adaptation to drought, cold, heavy metal, and other environmental stresses [18,19,25,26]. In the United States and New Zealand, numerous studies focused on the relationship between endophytes and tall fescue (Festuca arundinacea) and perennial ryegrass (Lolium perenne), which results in the tolerance and resistance of hosts to biotic and abiotic stresses [24,27,28,29,30]. The Northwest Plateau of China is undergoing severe soil erosion, with barren land and reduced forest cover, which leads to a decline in ecological functions. Water use efficiency is an important determinant of sustainable agricultural development in grasslands. The grass–endophyte relationship plays a role in improving water-use efficiency under drought conditions [31]. Yao [32] showed that drunken horse grass endophytes cause plants to competitively exclude other competitor plant species. The distribution and frequency of endophyte-infected (E+) drunken horse grass is more extensive than non-infected (E−) grass individuals in semi-arid and arid grasslands in Northwest China [18]. The interaction between fungal endophyte genus Epichloë and its host plants represents a unique model for examining ecological and biological benefits in fungal endophyte–plant interactions [23].
Studies showed that Epichloë endophytes have positive effects on host growth. However, far too little attention was paid to the mechanism by which fungal endophytes break seed dormancy in drunken horse grass. The central thesis of this paper is to investigate the interactive effect of Epichloë endophyte and various dormancy-breaking methods in A. inebrians from different origins. There are three primary aims of this study: 1. to investigate the Epichloë endophyte promotion of seed germination; 2. to evaluate the effects of dormancy-breaking methods on A. inebrians seed germination; 3. to compare levels of germination in seeds from various geographic origins with different climates.

2. Materials and Methods

2.1. Seed Materials

Seeds of A. inebrians were collected from six climatically different natural sites in July 2019 (Table 1). Half of the collected seeds were soaked into 200-times-diluted thiophanate methyl for 6 h to eliminate the endophyte [33] and labeled as E + 1 (primary generated endophyte-infected seeds) and E − 1 (primary generated endophyte-noninfected seeds). At each site, 15 E + 1 and E − 1 seeds were sown in seedling pots (65 × 28 × 65 mm), and this was repeated 3 times per site at Lanzhou University. Pots were arbitrarily placed in a greenhouse with a diurnal cycle of 25 °C and 20 °C day and night air temperatures, respectively. At the end of the growing stage, second-generation seeds were collected from each E + 1 and E − 1 plant and tested microscopically by aniline blue-lactic acid [34]. Then, they were labeled as E+ and E− seeds and stored at 4 °C until the next experiment.

2.2. Breaking Dormancy and Germination Experiment

Mechanical, thermal, and chemical treatments were compared in terms of their relative effectiveness in breaking the seed dormancy of drunken horse grass seeds. Mechanical treatment was achieved by a needle pin, which was used to tear the seed coat without piercing the embryo; thermal treatment was completed by soaking in warm water (25 °C) for 30 min; chemical dormancy break was accomplished by soaking in 98% H2SO4 for 30 min [35] and in exogenous GA 1 part per million (ppm) for 20 min [36]. Intact E+ and E− seeds’ different sites without any treatments were used as control seeds (CK) (Table 2). To determine the optimum breaking method, 50 replications of 6 origins of E+ and E− seeds of 4 different treatments were placed in Petri dishes with two layers of filter papers. Each Petri dish contained 100 seeds. Petri dishes were arbitrarily laid flat into growth chambers (LRG-250-LED, China)—25 °C, diurnal cycle of 12 h day and night, and 35% humidity. The number of germinated seeds was recorded daily until no further germination was observed. Germination was considered as achieved when the radicle protrusion was approximately 2 mm. Experiments were continued for 30 days. The final germination rate was calculated on the basis of the total number of filled seeds.

2.3. Determination of Germination Rate

Germination was monitored daily, and germinated seeds were counted and removed from Petri dishes. Germination was considered as achieved when the radicle protrusion was approximately 2 mm. Experiments were continued for 30 days. The final germination percentage (FGP) was calculated on the basis of the total number of filled seeds. Germination rate = total germinated seed/total seed number × 100. The relative germination rate was calculated by subtracting the germination rate of controls.

2.4. Determination of Soluble Sugar

The soluble sugar content was determined by the sulfuric acid-anthrone color method [37]. Treated and untreated seeds were ground in liquid nitrogen. Aliquots of 0.1 g of each sample were homogenized in 5 mL 95% (v/v) ethanol. After centrifugation, 1 mL supernatant was mixed with 4 mL anthrone reagent and heated in a boiling water bath for 10 min. Absorbance was recorded at 620 nm after cooling. The amount of sugar was determined by the standard curve prepared from glucose.

2.5. Determination of Internal Hormone Levels

High-performance liquid chromatography (HPLC) was applied to test internal hormones, GA, IAA, and ABA [38]. American Waters Acquity Arc type high-performance liquid chromatography (Milford, MA, USA) was used for determination. The chromatographic conditions were chromatographic column: Symmetry C18 column (4.6 mm × 250 mm, 5 μm); mobile phase: 10% methanol + 90% φ = 0.1% phosphoric acid; flow rate: 1.0 mL/min; injection volume: 10 μL; detection wavelength: 254 nm; column temperature: 30 °C. We ground the seeds with liquid nitrogen in a dark environment, accurately weighed 2.0 g, washed them with 5 mL 80% chromatographic methanol 3 times in a test tube, wrapped them in aluminum foil paper and placed them into a refrigerator at 4 °C for 12 h extraction. We shook the mixture once every hour to dissolve the hormone in the organic phase. After shaking, we centrifuged the mixture at 4 °C 8000 r/min for 10 min; drew the supernatant into a 10 mL centrifuge tube; and extracted the filter residue twice, with 80% chromatographic methanol (shaking and mixing each time) and the addition of 2.5 mL each time, before soaking for 1 h; and finally, we combined the filtrate and diluted to 10 mL. We took 2 mL in a vacuum centrifugal concentrator and rotary evaporation (38 °C) until dry. We reconstituted it with 1.0 mL of 50% chromatographic methanol and passed it through a 0.22 μm organic phase microporous filter membrane to a sample bottle for testing.

2.6. Data Analysis

A three-way fixed effects ANOVA (p < 0.05) was performed to evaluate the effects of endophyte infection status (E+ and E−), treatments (M1, M2, M3, and M4), original habitat and their interactions on cumulative seed germination. The means were compared using Tukey’s test at the 95% confidence level. The significant difference in endophyte status (E+ or E−) in seed germination under different treatments was tested with a posthoc test with multiple comparisons of the mean analysis following one-way ANOVA. The difference between E+ and E− seed germination under the same treatment was tested by an independent t-test (p < 0.05). Prior to the analysis, the germination percentage data were arcsine transformed to meet the assumption of homogeneity of variance in the ANOVA. All of the analyses were performed using the IBM Statistical Product and Service Solution (SPSS) software (version 19.0; SPSS China, Shanghai, China).

3. Results

3.1. Germination Rate

Germination rates of the untreated controls were relatively high and ranged from 78–87 % for E− seeds and 83–87 % for E+ seeds depending on the origin of seed (see Figure S1).

3.2. Physiological Elements

Overall, the relative content of soluble sugar under the M2 treatment was different from that under the other treatments (p < 0.001). Pair-wise comparisons of seed-germination were made between seeds with different endophyte statuses (E+ and E−) of the same origin. (p < 0.05) (Figure 1).
Except for E− seeds from YZ and YT under M1 treatment, all E+ seeds appeared to have a higher relative auxin content than E− seeds (Figure 2). Both E+ and E− seeds under M2 treatment showed a significant (p < 0.05) great relative soluble sugar content than other treatments, and all results were lager than 0. Each break-dormancy treatment was able to increase the germination.
Except for E− seeds from AL, which under M1 treatment, all E+ seeds showed a higher relative GA content than E− seeds (Figure 3). Both seed types under M2 treatment showed a significantly greater relative GA content than under other treatments, and all treatment results were positive compared to the CK condition.
The M2 treatment gave the greatest reduction in ABA content relative to the controls; all E+ seeds had a significantly lower ABA content increase than E− seeds (p < 0.05). ABA was higher under CK conditions than for the treated seeds, although differences were relatively small for M4 compared with M1–M3. All treated seeds showed a negative result when compared to that of untreated seeds (Figure 4).

3.3. Interactive Effects

On average, the interaction effect of origin, different breaking dormancy treatment and endophyte was significant for all indicators (p < 0.05) (Table 3). Two-way ANOVA analysis suggested that the origin*method, origin*endophyte, and method*endophyte were significant (p < 0.001). The germination rate and gibberellin had significant effects under interactive effect of origin, method, and endophyte (p < 0.05). On the other hand, there was no effect of various methods on either the soluble sugar or abscisic acid content inside plants (Table 3).

4. Discussion

The current study showed that Epichloë endophyte-infected Achantherum inebrians seeds collected in the Xiahe site under warm water soaking had the highest germination rate. The soluble sugar, IAA, and GA contents were increased, and stimulated the seed germination of A. inebrians.

4.1. Effects of Endophyte on Achnatherum inebrians Seed Germination

Early reported studies emphasized the importance of seed dormancy as a strategy of plants to adapt to adversity and protect species regeneration [39]. Seed dormancy has an important ecological significance and can effectively regulate the spatial and temporal distribution of seed germination [40]. We found the infected endophyte is able to significantly (p < 0.05) increase Achnatherum inebrins seed germination rate under any breaking dormancy method and any geographic origin (p < 0.05). Our study findings are in accordance with previous reported studies. Li [22] and Nan et al. [9] claimed that Epichloë endophyte-infected grass had increased growth, higher resistance to disease and showed stronger vigor under environmental stress compared to that of noninfected plants. Furthermore, Chen et al. [41] and Zhang et al. [19] found infected drunken horse grass had a higher resistance to multiple oxidative stresses. Miransari and Smith [11] highlighted that IAA was important evidence in establishing polarity, while GA played a crucial role in promoting embryo growth. Early germination was associated with the increase in IAA and GA amounts, and the inhibition of ABA production. Our results were also similar to those of Miransari and Smith [11], who showed that endophytic-infected seeds had a higher content of IAA, GA, and soluble sugar, and a lower content of ABA, which might be due to the possible hypothesis that endophytes promote internal hormones to stimulate the germination rate. We found that E+ seeds from any origin had a greater germination rate under the ‘control treatment’, which might lead one to speculate that endophytes would stimulate germination. However, there was a significant interaction between the origin and treatments of seeds (p < 0.05), suggesting that treatment effects were different for different locations, which corroborates similar findings by Bao et al. [17]. The current study proved that Epichloë endophyte significantly enhanced the seed germination of drunken horse grass, under either a low or high temperature, which justified the statement that endophyte increases competitive advantages [42,43].

4.2. Effects of Geographic Origin on Seed Germination

The Xiahe site has the highest elevation and lowest temperature range and showed a significantly higher seed germination rate than other origins. Koornneef et al. [44] reported that temperature and altitude are important factors for species distribution and crop reproduction under natural environmental change. Our experimental site (Xiahe) had a relatively cold atmosphere, which promotes seed germination genes. Bao et al. [17] found that high-altitude plants had a greater germination rate. Previous studies confirmed that plants from low temperature alpine regions have a higher germination rate than plants from arid regions. Endophyte-infected seeds can survive under a wide range of temperature conditions, and have the ability to endure harsh or suboptimum environments. It is hypothesized that mother plants have strong effects on seed/plant progeny, and Achnatherum inebrians is able to survive under harsh environments due to traits that are passed down from mother plants [45,46]. In addition to dormancy-breaking methods and endophyte status, we observed the effects of genetic basis and background elements from different origins on second-generation seed germination. This is due to the fact that mother plants adapt to local environment. We tested the germination rate of all materials at room temperature with stable humidity.

4.3. Effects of Dormancy Breaking Treatments on Seed Germination

Our result showed that under the M2 condition, the germination rates of both E+ and E− seeds were higher than other treatments; all germination rates were better than those of the CK condition for all geographic origins. We speculated that the dormancy of the Achantherum inebrains seed was due to the lack of imbibition, or due to chilling. When under needle treatment or 98% H2SO4 treatment, there was a scarcely greater germination rate compared to the CK condition, and GA solution soaking also had little effect; hence, we strongly suggested M2. Soitamo et al. [46] found that the colder the climate, the higher the ABA content; this conclusion would explain the increased amount of ABA in the experiment involving seeds from the Alxa League desert, where temperatures usually remain cool. ABA plays an active role in inducing seed dormancy and maintaining the dormancy state. A low ABA content during seed development causes primary dormancy in mature seeds, while too much ABA will enhance the secondary dormancy of seeds and delay germination [11]. In our study, we did not have direct data to prove the effect of GA and ABA on germination; however, according to the comparison of the trends, we suspect that there was a positive correlation between GA and germination, and there was a negative correlation between ABA and the germination rate. Bethke et al. [47] and Kucera et al. [10] proved that the endogenous hormones and external environment of seeds co-regulate seed dormancy and germination. ABA resynthesizes when the dormant seed blots, thus keeping the seed in a dormant state. The higher IAA, GA, and soluble sugar, but lower ABA and endophyte infection, promote seed germination, possibly due to the fact that the infection of endophyte might stimulate the production of internal hormones.
Our experiments showed a higher content of soluble sugars in A. inebrians seeds from the Xiahe site. Studies showed that germination rate increases with the increase in soluble sugar content, suggesting that soluble sugars play a positive role in supporting seed germination [13,48,49]. Wen et al. [50] reported that carbohydrate is the storage substance of plants, responsible for maintaining tissues during chilling, while IAA plays a positive role in maintaining GA/ABA ratios.

5. Conclusions

In summary, the present study was designed to determine the effects of various seed dormancy-breaking treatments, seed origins and Epichloë endophyte infection in Achnatherum inebrians on seed germination. These experiments confirmed that the infection of endophyte stimulates the germination rate, content of soluble sugar, IAA, and GA of seeds from different geographic origins. Water soaking significantly increased seed germination rates. This is the first study to examine the associations among plant–geographic origins, dormancy break methods and endophytes. The analysis extended our knowledge of how endophytes and internal substances interact in seeds of A. inebrians. The relationship between Epichloë endophyte and endogenous hormone levels in seeds had positive effects on germination. We propose that the effects of endophyte on seed germination and seedling vigor should be considered in future turfgrass breeding efforts.

Supplementary Materials

The following are available online at https://0-www-mdpi-com.brum.beds.ac.uk/article/10.3390/microorganisms9112183/s1, Figure S1: Germination rate of infected (E+) and non-infected (E−) Achnatherum inebrians from different treatments on an altitude (origin) gradient.

Author Contributions

Conceptualization, Y.C. and C.L.; methodology, Y.C.; software, K.S.; validation, J.F.W. and C.L.; formal analysis, Y.C.; writing—review and editing, Y.C.; supervision, C.L.; funding acquisition, C.L. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by the Strategic Priority Research Program of Chinese Academy of Sciences: XDA26020202; the Second Tibetan Plateau Scientific Expedition and Research (STEP) program: 2019QZKK0302; Fundamental Research Funds for the Central Universities: LZUJBKY-2021-kb10; 111 Project: B12002; USDA-NIFA Multistate Project: W4147 and Gansu Province Education Science and Technology Innovation Project: 2021CXZX-136.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Informed consent was obtained from all subjects involved in the study.

Data Availability Statement

Data available in a publicly accessible repository.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Bewley, J.D. Seed germination and dormancy. Plant Cell 1997, 96, 1055–1066. [Google Scholar] [CrossRef] [Green Version]
  2. Baskin, J.M.; Baskin, C.C.; Li, X. Taxonomy, anatomy and evolution of physical dormancy in seeds. Plant Species Biol. 2000, 15, 139–152. [Google Scholar] [CrossRef]
  3. Penfield, S. Seed dormancy and germination. Curr. Biol. 2017, 27, 874–878. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  4. Adkins, S.W.; Bellairs, S.M.; Loch, D.S. Seed dormancy mechanisms in warm season grass species. Euphytica 2020, 126, 13–20. [Google Scholar] [CrossRef]
  5. Abbasi, M.R. Breaking seed dormancy in some Iranian wild clovers (Trifolium spp.) selected as promising new germplasm. Genet. Res. Crop Evol. 2020, 67, 1577–1585. [Google Scholar] [CrossRef]
  6. Adkins, S.W.; Bellairs, S.M. Seed dormancy mechanisms in Australian native species. In Proceedings of the Third Native Seed Biology for Revegetation Workshop, Perth, Australia, 17–18 May 1995; Australian Centre for Minesite Rehabilitation Research: Kenmore, Australia, 2000. [Google Scholar]
  7. Baskin, J.M.; Schank, S.C.; West, S.H. Seed dormancy in 2 species of Digitaria from Africa. Crop Sci. 1969, 9, 584. [Google Scholar] [CrossRef]
  8. Keshtkar, A.; Keshtkar, H.; Razavi, S.; Dalfardi, S. Methods to break seed dormancy of Astragalus cyclophyllon. Afr. J. Biotechnol. 2010, 7, 3874–3877. [Google Scholar]
  9. Li, X.; Chen, L.; Gao, H.D. Endogenous screening of Torreya grandis seeds inhibiting their germination and growth. J. Southwest For. Univ. (Nat. Sci.) 2018, 38, 28–33. [Google Scholar]
  10. Kucera, B.; Cohn, M.A.; Leubner-Metzger, G. Plant hormone interactions during seed dormancy release and germination. Seed Sci. Res. 2005, 15, 218–307. [Google Scholar] [CrossRef]
  11. Miransari, M.; Smith, D.L. Plant hormones and seed germination. Environ. Exp. Bot. 2013, 99, 110–121. [Google Scholar] [CrossRef]
  12. Fennimore, S.A.; Foley, M.E. Genetic and physiological evidence for the role of gibberellic acid in the germination of dormant Avena fatua seeds. J. Exp. Bot. 1998, 49, 89–94. [Google Scholar] [CrossRef]
  13. Zhao, J.; Zhang, Z.H.; Hou, Q.Y.; Yu, F.Y. Investigation on dormancy characteristics of Styrax tonkinensis seeds. J. Cent. South Univ. For. Technol. 2019, 39, 45–51. [Google Scholar]
  14. Zhang, J.B. Variation of Storage Substances and Hormones during Cold Stratification for Seeds of Acer mono; Northeast Forestry University: Harbin, China, 2008. [Google Scholar]
  15. Zhao, Y.Y.; Song, C.C.; Brummell, D.A.; Qi, S.N.; Lin, Q.; Bi, J.F.; Duan, Y.Q. Salicylic acid treatment mitigates chilling injury in peach fruit by regulation of sucrose metabolism and soluble sugar content. Food Chem. 2021, 358, 129867. [Google Scholar] [CrossRef]
  16. Zhao, Y.Y.; Song, C.C.; Brummell, D.A.; Qi, S.N.; Lin, Q.; Bi, J.F.; Duan, Y.Q. Jasmonic acid treatment alleviates chilling injury in peach fruit by promoting sugar and ethylene metabolism. Food Chem. 2021, 338, 128005. [Google Scholar] [CrossRef] [PubMed]
  17. Bao, G.S.; Song, M.L.; Wang, Y.Q.; Saikkonen, K.; Wang, H.S. Interactive effects of Epichloë fungal and host origins on the seed germination of Achnatherum inebrians. Symbiosis 2019, 79, 49–58. [Google Scholar] [CrossRef]
  18. Li, C.J.; Gao, J.H.; Nan, Z.B. Interactions of Neotyphodium gansuense, Achnatherum inebrians, and plant-pathogenic fungi. Mycol. Res. 2007, 111, 1220–1227. [Google Scholar] [CrossRef] [PubMed]
  19. Zhang, X.X.; Li, C.J.; Nan, Z.B.; Matthew, C. Neotyphodium endophyte increases Achnatherum inebrians (drunken horse grass) resistance to herbivores and seed predators. Weed Res. 2012, 52, 70–78. [Google Scholar] [CrossRef]
  20. Ren, J.Z. Common poisonous plants in north-western grasslands of China. J. Gansu Agric. Univ. 1959, 1, 9–16. [Google Scholar]
  21. Bruehl, G.W.; Kaiser, W.J.; Klein, R.E. An endophyte of Achnatherum inebrians, an intoxicating grass of northwest China. Mycologia 1994, 86, 773–776. [Google Scholar] [CrossRef]
  22. Li, C.J.; Nan, Z.B.; Paul, V.H.; Dapprich, P.D.; Liu, Y. A new Neotyphodium species symbiotic with drunken horse grass (Achnatherum inebrians) in China. Mycotaxon 2005, 90, 141–147. [Google Scholar]
  23. Wang, J.F.; Hou, W.P.; Christensen, M.J.; Xia, C.; Chen, T.; Zhang, Z.X.; Nan, Z.B. The fungal endophyte Epichloe gansuensis increase NaCl-tolerance in Achnatherum inebrians through enhancing the activity of plasma membrane H+-ATPase and glucose-6-phosphate dehydrogenase. Sci. China Life Sci. 2021, 64, 452–465. [Google Scholar] [CrossRef]
  24. Moon, C.D.; Scott, B.; Schardl, C.L.; Christensen, M.J. The Evolutionary Origins of Epichloë Endophytes from Annual Ryegrasses. Mycologia 2000, 92, 1103–1118. [Google Scholar]
  25. Chen, N.; He, R.L.; Chai, Q.; Li, C.J.; Nan, Z.B. Transcriptomic analyses giving insights into molecular regulation mechanisms involved in cold tolerance by Epichloë endophyte in seed germination of Achnatherum inebrians. Plant Growth Regul. 2016, 80, 367–375. [Google Scholar] [CrossRef]
  26. Zhang, X.X.; Li, C.J.; Nan, Z.B. Effects of cadmium stress on growth and anti-oxidative systems in Achnatherum inebrians symbiotic with Neotyphodium gansuense. J. Hazard Mater. 2010, 175, 703–709. [Google Scholar] [CrossRef] [PubMed]
  27. Clay, K.; Schardl, C. Evolutionary origins and ecological consequences of endophyte symbiosis with grasses. Am. Nat. 2002, 160, 99–127. [Google Scholar] [CrossRef]
  28. Leuchtmann, A.; Bacon, C.W.; Schardl, C.L.; White, J.F.; Tadych, J.M. Nomenclatural realignment of Neotyphodium species with genus Epichloë. Mycologia 2014, 106, 202–215. [Google Scholar] [CrossRef] [PubMed]
  29. Simpson, W.R.; Faville, M.J.; Moraga, R.A.; Williams, W.M.; Mcmanus, M.T.; Johnson, R.D. Epichloë fungal endophytes and the formation of synthetic symbioses in Hordeeae (1⁄4 Triticeae) grasses. J. Syst. Evol. 2014, 52, 794–806. [Google Scholar] [CrossRef]
  30. Thom, E.R.; Popayt, A.J.; Waugh, C.D.; Minnee, E.M.K. Impact of novel endophytes in perennial ryegrass on herbage production and insect pests from pastures under dairy cow grazing in northern New Zealand. Grass Forage Sci. 2013, 69, 191–204. [Google Scholar] [CrossRef]
  31. Bacon, C.W. Abiotic stress tolerances (moisture, nutrients) and photosynthesis in endophyte-infected tall fescue. Agric. Ecosyst. Environ. 1993, 44, 123–142. [Google Scholar] [CrossRef]
  32. Yao, X. Effect of Achnatherum inebrians—Epichloe gansuensis Symbiont on Plant Composition and Soil Microbial Community Diversity in Rangelands; Lanzhou University: Lanzhou, China, 2019. [Google Scholar]
  33. Li, N.N.; Zhao, Y.F.; Xia, C.; Zhong, R.; Zhang, X.X. Effects of thiophanate methyl on seed borne Epichole fungal endophyte of Achnatherum inerbians. Pratacult. Sci. 2016, 10, 1306–1314. [Google Scholar]
  34. Bacon, C.W.; White, J.F. Microbial Endophytes; Marcel Dekker: New York, NY, USA, 1994; pp. 341–388. [Google Scholar]
  35. Carruggio, F.; Onofri, A.; Impelluso, C.; Giusso del Galdo, G.; Scopece, G.; Cristaudo, A. Seed Dormancy Breaking and Germination in Bituminaria basaltica and B. bituminosa (Fabaceae). Plants 2020, 9, 1110. [Google Scholar] [CrossRef]
  36. Grappin, P.; Bouinot, D.; Sotta, B.; Miginiac, E.; Jullien, M. Control of seed dormancy in Nicotiana plumbaginifolia: Post-imbibition abscisic acid synthesis imposes dormancy maintenance. Planta 2000, 210, 279–285. [Google Scholar] [CrossRef]
  37. Bano, C.; Amist, N.; Singh, N.B. UV-B radiation escalate allelopathic effect of benzoic acid on Solanum lycopersicum L. Sci. Hortic. 2017, 220, 199–205. [Google Scholar] [CrossRef]
  38. Chen, X.P.; Wang, X.F.; Sun, X.L.; Zhao, Z.Z. Determination of gibberellin abbeymycin and abscisic acid in cucumber by high-performance liquid chromatography. Shandong Agric. Sci. 2005, 226, 526–532. [Google Scholar]
  39. Fu, N.; Song, H.; Wang, S.J.; Xie, H.F.; Wei, M.H.; Xing, L.; Zhang, Y.; Liu, J.R. Research progress on seed dormancy and breaking methods. J. Anhui Agric. Sci. 2018, 46, 10–12. [Google Scholar]
  40. Finch-Savage, W.E.; Leubner-Metzger, G. Seed dormancy and the control of germination. New Phytol. 2006, 171, 501–523. [Google Scholar] [CrossRef]
  41. Chen, L.; Li, X.Z.; Li, C.J.; Swoboda, G.A.; Young, C.A.; Sugawara, K.; Leuchtmann, A.; Schardl, C.L. Two distinct Epichloë species symbiotic with Achnatherum inebrians, drunken horse grass. Mycologia 2015, 107, 863–873. [Google Scholar] [CrossRef] [Green Version]
  42. Gundel, P.E.; Maseda, P.H.; Ghersa, C.M.; Benech-Arnolo, R. Effects of the Neotyphodium endophyte fungus on dormancy and germination rate of Lolium multiflorum seeds. Aust. Ecol. 2006, 31, 767–775. [Google Scholar] [CrossRef]
  43. Fuchs, B.; Krischke, M.; Mueller, M.J.; Krauss, J. Plant age and seasonal timing determine endophyte growth and alkaloid biosynthesis. Fungal Ecol. 2017, 29, 52–58. [Google Scholar] [CrossRef]
  44. Koornneef, M.; Bentsink, L.; Hilhorst, H. Seed dormancy and germination. Curr. Opin. Plant Biol. 2002, 5, 33–36. [Google Scholar] [CrossRef] [Green Version]
  45. White, C.N.; Rivin, C.J. Gibberellins and seed development in maize. II. Gibberellin synthesis inhibition enhances abscisic acid signaling in cultured embryos. Plant Physiol. 2000, 122, 1089–1097. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  46. Soitamo, A.J.; Piippo, M.; Allahverdiyeva, Y.; Battchikova, N.; Aro, E.M. Light has a specific role in modulating Arabidopsis gene expression at low temperature. BMC Plant Biol. 2008, 8, 13. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  47. Bethke, P.C.; Libourel, I.G.; Aoyama, N.; Chung, Y.Y.; Still, D.W.; Jones, R.L. The Arabidopsis aleurone layer responds to nitric oxide, gibberellin, and abscisic acid and is sufficient and necessary for seed dormancy. Plant Physiol. 2007, 1436, 1173–1188. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  48. Bao, J.P.; Zhang, S.L. Changes in germination, storage materials and antioxidant enzyme activities in pear (Pyrus betulaefolia Bge. and Pyrus calleryana Dcne.) stock seeds during cold stratification. Seed Sci. Technol. 2011, 39, 655–659. [Google Scholar] [CrossRef]
  49. Valenzuela-Núez, L.M.; Briceo-Contreras, E.A.; Esparza-Rivera, J.R.; Pea, G.; Núez-Colima, J.A. Seasonal changes in soluble sugar concentration in pecan perennial organs (Carya Illinoiensis (Wangenh) Koch). Acta Univ. 2019, 29, 1–13. [Google Scholar]
  50. Wen, B.B.; Zhang, X.H.; Chen, X.D.; Gao, D.S.; Zhu, C.Y.; Xiao, W. Physiological changes of peach cultivars with three different chilling requirement during dormancy induction. J. Shandong Agric. Univ. (Nat. Sci. Ed.) 2018, 50, 1–5 + 74. [Google Scholar]
Microorganisms 09 02183 g001 550
Figure 1. Relative soluble sugar content of infected (E+) and noninfected (E−) Achnatherum inebrians from different treatments on an altitude (origin) gradient. Different capital letters indicate mean significant difference (p < 0.05) in endophyte status (E+ or E−) in seed germination under different origin. Different lowercase letters indicate mean significant difference (p < 0.05) in pair-wise comparisons of endophyte status (E+ and E−) in seed germination in same origin.
Figure 1. Relative soluble sugar content of infected (E+) and noninfected (E−) Achnatherum inebrians from different treatments on an altitude (origin) gradient. Different capital letters indicate mean significant difference (p < 0.05) in endophyte status (E+ or E−) in seed germination under different origin. Different lowercase letters indicate mean significant difference (p < 0.05) in pair-wise comparisons of endophyte status (E+ and E−) in seed germination in same origin.
Microorganisms 09 02183 g001
Microorganisms 09 02183 g002 550
Figure 2. Relative auxin content of infected (E+) and non-infected (E−) Achnatherum inebrians from different methods on an altitude (origin) gradient. The different capital letters indicate the mean significant difference (p < 0.05) in endophyte status (E+ or E−) in seed germination under different origin. Different lowercase letters indicate the mean significant difference (p < 0.05) in the pair-wise comparisons of endophyte status (E+ and E−) in seed germination in the same origin.
Figure 2. Relative auxin content of infected (E+) and non-infected (E−) Achnatherum inebrians from different methods on an altitude (origin) gradient. The different capital letters indicate the mean significant difference (p < 0.05) in endophyte status (E+ or E−) in seed germination under different origin. Different lowercase letters indicate the mean significant difference (p < 0.05) in the pair-wise comparisons of endophyte status (E+ and E−) in seed germination in the same origin.
Microorganisms 09 02183 g002
Microorganisms 09 02183 g003 550
Figure 3. Relative gibberellin content of infected (E+) and non-infected (E−) Achnatherum inebrians from different treatments on an altitude (origin) gradient. The different capital letters indicate the mean significant difference (p < 0.05) in endophyte status (E+ or E−) in seed germination under different origin. The different lowercase letters indicate the mean significant difference (p < 0.05) in the pair-wise comparisons of endophyte status (E+ and E−) in seed germination in the same origin.
Figure 3. Relative gibberellin content of infected (E+) and non-infected (E−) Achnatherum inebrians from different treatments on an altitude (origin) gradient. The different capital letters indicate the mean significant difference (p < 0.05) in endophyte status (E+ or E−) in seed germination under different origin. The different lowercase letters indicate the mean significant difference (p < 0.05) in the pair-wise comparisons of endophyte status (E+ and E−) in seed germination in the same origin.
Microorganisms 09 02183 g003
Microorganisms 09 02183 g004 550
Figure 4. Abscisic acid content of infected (E+) and noninfected (E−) Achnatherum inebrians from different methods on an altitude (origin) gradient. Different capital letters indicate mean significant difference (p < 0.05) in endophyte status (E+ or E−) in seed germination under different origin. Different lowercase letters indicate mean significant difference (p < 0.05) in pair-wise comparisons of endophyte status (E+ and E−) in seed germination in same origin.
Figure 4. Abscisic acid content of infected (E+) and noninfected (E−) Achnatherum inebrians from different methods on an altitude (origin) gradient. Different capital letters indicate mean significant difference (p < 0.05) in endophyte status (E+ or E−) in seed germination under different origin. Different lowercase letters indicate mean significant difference (p < 0.05) in pair-wise comparisons of endophyte status (E+ and E−) in seed germination in same origin.
Microorganisms 09 02183 g004
Table
Table 1. Origins of Achnatherum inebrians plant lineages and their attributes.
Table 1. Origins of Achnatherum inebrians plant lineages and their attributes.
LocationLongitude and LatitudeElevation (m) Mean Temperature (°C)Mean Precipitation (mm)
Gansu-Yuzhong (YZ)35°56′26.7″ N18506.6320
104°02′48.9″ E
Gansu-Yingtai (YT)36°52′42.7″ N22795.3331
103°47′19.8″ E
Gansu-Xiahe (XH) 35°32′16.4″ N35002.6516
102°25′36.7″ E
Ningxia-Haiyuan (HY)36°36′9″ N17327286
105°39′46″ E
Alxa League (AL)38°39′15″ N18308113
105°44′21″ E
Alxa Desert (ALD)38°56′16″ N16607.739
105°47′39″ E
Table
Table 2. Experimental design of germination tests conducted in laboratory.
Table 2. Experimental design of germination tests conducted in laboratory.
Break Dormancy MethodImmersion TimeTemperature
Needle pin (M1)/22 ± 2 °C
Water soaking (M2)30 min25/20 °C
98% H2SO4 soaking (M3)20 min22 ± 2 °C
Exogenous GA soaking(M4)30 min22 ± 2 °C
Control (CK)/22 ± 2 °C
Table
Table 3. Effects of origin, endophyte, dormancy-breaking method, and their interaction on germination and content of soluble sugar, gibberellin, auxin, and abscisic acid in seeds of Achnatherum inebrians. Df = degree of freedom, F = f value is ratio of two means to effect/error term, p = significance.
Table 3. Effects of origin, endophyte, dormancy-breaking method, and their interaction on germination and content of soluble sugar, gibberellin, auxin, and abscisic acid in seeds of Achnatherum inebrians. Df = degree of freedom, F = f value is ratio of two means to effect/error term, p = significance.
Source of VariationdfGermination RateSoluble SugarGibberellinAuxinAbscisic Acid
FpFpFpFpFp
Origin553.01<0.001992.18<0.001455.01<0.00159.37<0.00119.18<0.001
Method4438.88<0.001193.03<0.0011510.96<0.00135,819.20<0.0013909.35<0.001
Endophyte1563.25<0.00162.07<0.0012.63<0.051.55<0.0510.42<0.001
Origin*Method204.38<0.0013.13<0.00171.71<0.0011.670.222.51<0.001
Origin*Endophyte52.090.0716.27<0.0010.990.421.110.363.95<0.001
Method*Endophyte410.68<0.0011.400.244.72<0.0010.630.652.060.09
Origin*Method*Endophyte202.24<0.0010.770.741.70<0.051.680.051.520.09
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Share and Cite

MDPI and ACS Style

Chen, Y.; Su, K.; Li, C.; White, J.F. Interactive Effects of Epichloë Endophyte, Dormancy-Breaking Treatments and Geographic Origin on Seed Germination of Achnatherum inebrians. Microorganisms 2021, 9, 2183. https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms9112183

AMA Style

Chen Y, Su K, Li C, White JF. Interactive Effects of Epichloë Endophyte, Dormancy-Breaking Treatments and Geographic Origin on Seed Germination of Achnatherum inebrians. Microorganisms. 2021; 9(11):2183. https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms9112183

Chicago/Turabian Style

Chen, Yaqi, Kaiqi Su, Chunjie Li, and James F. White. 2021. "Interactive Effects of Epichloë Endophyte, Dormancy-Breaking Treatments and Geographic Origin on Seed Germination of Achnatherum inebrians" Microorganisms 9, no. 11: 2183. https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms9112183

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop