A brief presentation on ' abiotic stress management strategies by microbes'.

1. TOPIC :MICROBE MEDIATED
STRATEGIES FOR ABIOTIC STRESS
MANAGEMENT
PRESENTED BY:
TEJASWINI PETKAR

2. CONTENTS
• INTRODUCTION
• AGAINST HIGH TEMPERATURE CONDITIONS
• DROUGHT TOLERANCE
• AGAINST EXTREME LOW TEMPERATURE CONDITIONS
• AGAINST HIGH SALINITY
• INDUCTION OF ABIOTIC STRESS TOLERANCE IN PLANTS BY ENDOPHYTIC MICROBES
• TRANSGENIC PLANTS AGAINST ABIOTIC STRESS
• FORMULATION OF METHYLOBACTERIUM
• CONCLUSION
• REFERENCES

3. INTRODUCTION
• Abiotic stresses affect plants in different ways and are causes of reduction in crop
productivity and are hence are the foremost limiting factors for agricultural
productivity.
• In order to increase crop productivity it becomes necessary to evolve efficient low-
cost technologies for abiotic stress management.
• Microorganisms, the most natural inhabitants of diverse environments exhibit
enormous metabolic capabilities to mitigate abiotic stresses.
• Microorganisms especially those surviving in the soil under extreme conditions, have
shown great properties, which, if exploited can serve agriculture for increasing and
maintaining crop productivity.
• Several studies have reported that soil microorganisms may have mechanisms for
alleviation of abiotic stresses in plants such as water and temperature stress, salinity,
heavy metals etc.
• Induced Systemic Tolerance (IST) is the term being used for microbe-
mediated induction of abiotic stress responses.
• The microbes with their unique metabolic and genomic abilities can alleviate
abiotic stress conditions in a natural way without disturbing the ecosystem.

4. • Some of these include tolerance to salinity, drought (Azospirillum sp.,
Pseudomonas syringae, P. fluorescens, Bacillus sp.) and nutrient deficiency
(Bacillus polymyxa, Pseudomonas alacaligenes).
• On a general note, among abiotic stresses, there are some common principles
at work, particularly with regard to root/soil interactions and the physiological
changes in the root system induced by microorganisms, namely:
 Stimulation of root growth through bacterially produced IAA (and/or nitric
oxide) under drought, nutrient deficiency, salinity and metal toxicity stress;
 Decrease in host plant stress ethylene level by bacterial ACC deaminase
activity under drought, salinity, heavy metal toxicity and flooding conditions;
 Induced changes in cell wall/cell membrane under drought and suboptimal
temperature conditions.

7. Various stresses caused by abiotic factors on plants

8. Effect of different types of abiotic factors (stresses) on plants

9. AGAINST HIGH TEMPERATURE
CONDITIONS
• Water scarcity also leads to temperature increase.
• Similar to other stresses, microbes, which themselves are
thermotolerant, can also be used for conferring temperature tolerance
to crops.
• Higher temperature results in extensive denaturation and aggregation
of cellular proteins, which, if unchecked, lead to cell death.
• The ability of a thermotolerant strain of Pseudomonas AKM-P6 was
used to alleviate the heat stress in sorghum seedlings (Ali et al., 2009).
• Recent research has shown that soil microbes can help plants like
wheat, rice , pepper and maize to withstand high temperature.

10. • Soil or foliar application of Methylobacterium colonize the plant and
interact with the endophytic microbial community in turn
preventing the crops from adverse temperature fluctuations.
• Pseudomonas sp. strain NBRI0987 causes thermotolerance in
sorghum seedlings, which consequently synthesize high molecular
weight proteins in leaves thus increasing the plant biomass.
• The bacterium Burkholderia phytofirmans PSJN colonizes grapevine
residues and protects the plant against heat through increases in
the levels of starch, and proline and phenols.

11. DROUGHT TOLERANCE
• Water stress is perhaps the most alarming condition faced by a plant, as it affects
the water relations of a plant at cellular and whole plant level, decreasing
productivity and causing economic losses in agriculture.
• Drought decreases germination rates, causes inhibition of photosynthesis, loss of
membrane integrity and increased generation of reactive oxygen species
(Greenberg et al., 2008).
• Prolonged water stress causes decline in leaf water potential and stomatal
opening, reduces leaf size, suppresses root growth, reduces seed number, size,
and viability, delays flowering and fruiting and limits plant growth and
productivity (Xuet al., 2016).
• One of the earliest reports on induction of drought tolerance by PGPR was that
by Timmusk and Wagner (1999) in Arabidopsis thaliana. They showed that
Paenibacillus polymyxa induced tolerance against drought by over-expression of
drought-responsive gene ERD15 (EARLY RESPONSE TO DEHYDRATION).
• It was further shown in wheat that inoculation of Azospirillum brasilense Sp245
under low water regime resulted in a better water status and an additional
‘elastic adjustment’ leading to better grain yield and mineral quality (Creus et al.,
2004).

12. • As a response to water deficit, plants increase the synthesis of osmolytes
such as glycine betaine, exudated by root zone bacteria increasing the
osmotic potential within cells (Farooq et al. 2009).
• Glycine betaine produced by osmo-tolerant bacteria can possibly act
synergistically with plant-produced glycine betaine in response to the stress,
and this way, increase drought tolerance .
• Another important factor in the growth stimulation of these osmo-tolerant
bacteria is their ability to produce IAA. Improvement in root proliferation in
inoculated drought-stressed rice plants is likely to be induced by this
hormone (Yuwono et al. 2005), apparently for enhanced water uptake.
• The ACC deaminase activity of Achromobacter piechaudi was shown to
confer tolerance to water deficit in tomato and pepper, resulting in
significant increases in fresh and dry weights. Bacteria occurring on root
surfaces containing ACC deaminase have been shown to modify the
sensitivity of root and leaf growth to soil drying, apparently by influencing
ethylene signalling.

13. • Plants treated with exopolysaccharide (EPS)-producing bacteria display
increased resistance to water stress (Bensalim et al., 1998). The EPS-
producing strain Pseudomonas putida strain GAP-P45 forms biofilm on the
root surface of sunflower seedlings and imparts tolerance to plants against
drought stress. The inoculatedseedlings showed improved soil aggregation
and root-adhering soil and higher relative water content (RWC) in the leaves
(Sandhya et al., 2009, 2011).
• Susceptibility to water deficiency has been shown to be correlated with
membrane damage and lipid composition (Wilson, Burke & Quisenberry
1987; Moran et al. 1994). Cell membranes constitute important interfaces
within a complex system regulating a plant’s physiological status, and
rhizobacteria can influence processes taking place at these sites.

14. AGAINST EXTREME LOW TEMPERATURE
CONDITIONS
• Low temperature impairs metabolic processes, through alterations
in membrane properties, changes in structure of proteins and
interactions between macromolecules as well as inhibition of
enzymatic reactions in plants.
• Several workers have also reported the ability of cold-tolerant
bacteria to induce cold tolerance in plants (Barka et al., 2006;
Chang et al., 2007; Selvakumar et al., 2008a, b; Mishra et al.,
2009a, b).
• Since ice nucleation has been recognized as a cause of frost
damage of plants, attempts are now being made to identify
bacteria from the phyllosphere which have low ice nucleating
activity and use them as foliar sprays with a view to overcome
frost damage (Selvakumar et al., 2012).

15. ICE-MINUS BACTERIA:
• Ice-minus bacteria is a common name given to a variant of the
common bacterium Pseudomonas syringae (P. syringae).
• Like raindrops, snowflakes are created by water molecules clustering
around a nucleus. This nucleus can be a particle of soot or dust, but in
the vast majority of cases it is a bacterium of the species
Pseudomonas syringae.
• Water molecules cluster around special proteins on the surface of
the bacterium. If the temperature is low enough, these will form
enormous ice crystals.
• The ice nucleating nature of P. syringae incites frost development,
freezing the buds of the plant and destroying the occurring crop.

16. • The introduction of an ice-minus strain of P. syringae to the surface
of plants would reduce the amount of ice nucleate present,
rendering higher crop yields.
• The recombinant form was developed as a commercial product
known as Frostban.
• Field-testing of Frostban in 1987 was the first release of a
genetically modified organism into the environment. The testing
was very controversial and drove the formation of US biotechnology
policy. Frostban was never marketed.
To protect themselves against freezing water,
many microbes produce antifreeze proteins
The bacterium Pseudomonas syringae is carried
into the air as moisture evaporates from leaves.

17. AGAINST HIGH SALINITY
• Increasing salinity is a major environmental stress and is perceived as a
substantial constraint to crop production.
• Exposure to salinity results in ion toxicity (Munns and Tester., 2008).
• The impacts of salinity include- low agricultural productivity, low economic
returns and soil erosions, (Hu and Schmidhalter., 2002).
• Soil salinity stresses plants in two ways: high concentrations of salts in the
soil make it harder for roots to extract water and high concentrations of salts
within the plant can be toxic.
• Salts on the outside of the roots have an immediate effect on cell growth
and associated metabolism; toxic concentrations of salts take time to
accumulate inside plants, before they affect plant function (Munns & Tester.,
2008).
• It is expected that with increasing salinization of cultivable land, within the
next 25 years there would be a land loss of 30%, which could increase up to
50% by the middle of this century linked with devastating global effects
(Wang et al., 2003).

18. • Studies have shown that inoculation with endophytic bacteria can mitigate
the effects of salt stress in different plant species.
• Azospirillum-inoculated seeds of lettuce (Lactuca sativa L., cv.Mantecosa),
for instance, showed better germination rates and vegetative growth than
non-inoculated control plants when exposed to NaCl (Barassi et al. 2006).
• In groundnut grown under saline field conditions, the plant growth-
promoting effects of ACC deaminase possessing Pseudomonas fluorescens
TDK1 were more pronounced, compared to strains lacking the enzyme
(Saravanakumar & Samiyappan 2007).
( ACC deaminases have been shown to modify the sensitivity of root and leaf
growth to soil drying, apparently by influencing ethylene signalling).
• Consistent with this, transgenic canola expressing a bacterial ACC deaminase
gene was shown to be more tolerant to high concentrations of salt than non-
transformed control plants (Sergeeva, Shah & Glick 2006).
• Similarly, inoculation of pepper with Bacillus sp.TW4 led to relief from
osmotic stress, which is often manifested as salinity (and/or drought)
stress(Jung, Kim & Hwang., 2003).

19. • Inoculation of wheat seedlings with bacteria that produce
exopolysaccharates (EPS) affect the restriction of sodium uptake and
stimulation of plant growth under conditions of stress caused by high
salinity (Ashraf et al., 2004, cit. Grover et al., 2010).
• Corn, beans and clover inoculated with AM fungi improved their
osmoregulation and increased proline accumulation which resulted
in salinity resistance (Feng et al., 2002, cit. Grover et al., 2010).
• Investigations on the interaction of PGPB with other microbes and
their effect on the physiological response of crop plants under
different soil salinity regimes are still at an incipient stage (Singh et
al., 2011).
• Alleviation of salt stress by PGPB inoculants has been shown in
rice(Rangarajan et al. 2003; Sapsirisopa et al. 2009; Nautiyal et al.
2013), wheat (Egamberdiyeva 2009), maize (Egamberdiyeva 2007),
cotton (Yao et al. 2010), lettuce (Han & Lee 2005), tomato (Mayak et
al. 2004), and pepper (del-Amor & Cuadra-Crespo 2012; Siddikee et
al. 2011).

21. AGAINST TOXICITY IN THE
ENVIRONMENT
• Rapid industrialization and population explosion has resulted in
the generation and dumping of various contaminants to the
soil.
• Heavy metals now present interfere with numerous
biochemical and physiological processes including
photosynthesis, respiration, nitrogen and protein metabolism,
and nutrient uptake in plants (Zhang et al., 2009).
• Microbial-mediated bioremediation offers great potential to
reinstate the contaminated environment (soil) in an
ecologically acceptable approach.
• Heavy metals tend to inhibit nodulation. i.e., they interrupt the
rate of symbiosis between plants and microsymbionts depends
on heavy metals concentration in soil.

22. • Heavy metals such as Cd, Ni, and Pb disrupt
the water regimen in plants.
• Proline accumulation in plant cells is a
biomarker for stress induced by heavy metals.
• The symbiotic associations between
Rhizobium/Bradyrhizobium and leguminous
plants are sensitive to the presence of heavy
metals in soil (Govedarica et al., 1997).
• Studies have shown that the effect of nickel
on the microbiological soil properties
depended on the microbial group and
agricultural plant species (Kastori et al., 2006;
Miloševic et al., 2002).
• Microorganisms bind soluble heavy metals in
three ways (biosorption, bioaccumulation,
and the binding by metabolic products),
which indirectly reduce the negative impact
of heavy metals on plants (Govedarica et al.,
1997).
Possible sources of entry of
toxic compounds and
heavy metals to the soil.

23. • Methylobacterium oryzae and Burkholderia sp. reduce nickel and
cadmium stress in tomato by reducing their uptake and translocation
(Marquez et al., 2007; Madhiyan et al.,2007).
• Inoculation with rhizobacteria alleviates abiotic stresses to plants
caused by drought, salinity and metal toxicity (Dimkpa et al., 2009).
• These authors pointed out that the bacteria that are used as
biofertilizers are at the same time plant bioprotectants against stress.
This interaction between plants and rhizobacteria (e.g., Bacillus)
mitigates stress conditions.

24. • Role of plant microbiome in defense mechanism. Microorganism in association with plants
activates different mechanism in response to abiotic stress conditions. PGPB: Plant growth
promoting bacteria, ACC: 1-aminocyclopropane- 1-carboxylate PAMPs/MAMPs: Pathogen-
associated molecular patterns or microbe-associated molecular patterns PRR: Pattern recognition
receptor AHLs: N-acyl-homoserine lactones.(Source :Syed Uzma Jalil et al., 2018 ; Role of plant
microbiome in abiotic stress tolerance)

25. INDUCTION OF ABIOTIC STRESS
TOLERANCE IN PLANTS BY ENDOPHYTIC
MICROBES
• Environmental stress to plants is more detrimental than biotic stress.
• Endophytes are microorganisms including bacteria and fungi that survive
within healthy plant tissues and promote plant growth under stress.
• Endophytes are microorganisms residing inside healthy plant tissues
without causing any apparent harm to the host (Bacon and White., 2000).
• Endophytes are well recognized for plant growth promotion and
production of natural compounds.
• The property of endophytes to induce stress tolerance in plants can be
applied to increase crop yields.

26. • Variations in the outside environment puts the plant metabolism out
of homeostasis which creates necessity for the plant to harbour
some advanced genetic and metabolic mechanisms within its
cellular system (Gill and Tuteja 2010) herein the importance of
microbes, especially the endophytes increases immensely.
• Studies conducted on Arthrobacter sp and Bacillus sp. isolated from
pepper plant showed significant reduction in upregulation and even
down regulation of some stress-inducible genes when compared
with gene expression in uninoculated plants.
• Phomaglomerata and Penicillium sp. significantly increased plant
biomass, related growth parameters, assimilation of essential
nutrients such as potassium, calcium, magnesium and reduced the
sodium toxicity in cucumber plants under sodium chloride and
polyethylene glycol–induced salinity and drought stress when
compared with control plants (Waqas et al.,2012).

27. MYCORRHIZAL FUNGI
• Other than beneficial bacteria, either free living or symbiotic, most the
terrestrial plants have a symbiotic association in their root system with a group
of fungi known as arbuscular mycorrhizal fungi (AMF). Such plants have an
improved ability for nutrient acquisition and exhibit enhanced tolerance to
different stresses while the fungus acquires a protected ecological niche and
plant photosynthates (Smith and Read, 2008).
• Several studies have revealed that AMF spore population in the soil increases
during both water and salt stress, resulting in enhanced tolerance.
• Although it is clear that AMF mitigate growth reduction caused by osmotic
stress, the mechanism involved remains unresolved (Ruíz-Lozano et al., 2012).
• While studying the influence of salinity on mycorrhizal association, it was
revealed that the fungal development was affected, reducing fungal mycelia
formation and host root colonization (Giri et al.,2007; Sheng, M. et al., 2008).
• Endophyte associated plants (panic grass, rice, tomato and dune grass)have
been reported to use significantly less water, increased biomass than in non-
symbiotic plants.

28. • The drought tolerance phenomenon may be explained by enhanced
accumulation of solutes in tissues of endophyte -infected plants as
compared to non-infected plants, or by reduced leaf conductance and a
slowdown of the transpiration stream, or due to thicker cuticle
formation (Malinowski and Belesky.,2000).
• Characterization of Trichoderma/ Theobromacacao revealed changes in
gene expression patterns which imply the possibility that Trichoderma
spp. could induce tolerance to abiotic stresses, possibly including
drought, in cacao (Bailey et al., 2006).
• P. indica induces salt tolerance in barley by increasing the levels of
antioxidants (Baltruschat et al., 2008).
• On constant exposure to 500 mM NaCl solution (sea water levels to
mimic exposure of plants in their native beach habitat), non symbiotic
plants Leymusmollis (dunegrass) became severely wilted and
desiccated within 7 days and were dead after 14 days. In contrast,
symbiotic plants infected with Fusarium culmorum did not show wilting
symptoms until they were exposed to 500 mMNaCl solution for 14 days
(Rodriguez et al. 2008).

30. TRANSGENIC PLANTS AGAINST ABIOTIC
STRESS
• A number of genes induced in response to
abiotic stresses have been identified from a
range of organisms adapted to stressful
environment.
• Genetic engineering is alternative because
of its potential to improve abiotic stress
tolerance more rapidly.
• The techniques for gene transformation of
crop plants have been applied for
identification of genes responsible for
abiotic resistance and their transfer.

31. Fig.: Plant response of a transgenic to abiotic stress to develop tolerance or resistance

32. • Lilius et al (1996) transformed tobacco plants with Δ'adi gene.
 Δ'adi gene which encodes for choline dehydrogenase protein (responsible
for conversion of choline to betaine aldehyde) from E. coli.
 The Δ'adi gene introduction rendered the transgenic tobacco plants
tolerant to high concentration of salt.
• Trehalose is a non-reducing disaccharide of glucose that functions as a
protectant in the stabilization of biological structure and enhances the
tolerance of organisms to abiotic stress.
 Zhang et al (2005) transformed tobacco plants with trehalose synthetase
(Tsase) gene for manipulating abiotic stress tolerance.
 Bacterial trehalose-6-phosphate (OtsB) genes introduced in tobacco
showed better growth under drought stress ( Pilon- Smits et al.,1995).
 Transgenic plants also showed a better capacity to retain water and
preformed more efficient photosynthesis under stress.
 The trehalose synthetase gene (TSase) gene from Grifola frondosa was
transferred into sugarcane (Wang et al., 2003b).

33. • Transgenic rice carrying barley HVA1 gene had shown drought resistance
(Xu et al., 1996).
 Gene HVA1 encodes for a group of three LEA or Late-embryogenesis-
abundant (LEA) proteins which get accumulated in vegetative organs
during drought condition.
 It has been suggested that LEA type proteins act as water binding
molecules, in ion sequestration and membrane stabilization.
 LEA-proteins are also encoded by Responsive to Dehydration (RD), Early
Responsive to Dehydration (ERD), cold inducible (KIN), cold regulated
(COR) and responsive to ABA (RAB) genes in different plant species.
 Transgenic rice showed enhanced accumulation of the HVA1 protein,
which led to higher growth rates, delayed stress-related damage systems
and improved recovery from the removal of stress conditions (Xu et al.,
1996).
• Potato plants (Solanum tuberosum cv. Desiree) transformed with yeast
invertase gene acquired a higher tolerance to cold temperature as
compared to the control plants, apparently due to the changes in sugar
ratio produced by the foreign invertase.

34. • Shou et al (2004) transformed maize with a tobacco MAPKKK
(NPK1).
 They found that the NPK1 expression enhanced drought
tolerance in transgenic maize.
 Expression of mitogen-activated protein kinase gene (MAPK)
genes activates an oxidative signal cascade and lead to the
tolerance of freezing, drought, heat and salinity stressing
transgenic tobacco.

35. Adaptations of transgenic plants to abiotic stresses
(Source : google images)

36. List of transgenic research for salt stress tolerance
Source: https://scialert.net

37. Table: Cold tolerance genes/transgenic plants
Source: https://scialert.net

38. Table: Gene encoding for molecular chaperones and transgenic development

39. Table : Transgenics developed in different crop plants against waterlogging
tolerance

40. FORMULATION OF METHYLOBACTERIUM
• Volatile carbon substrates, particularly the plant cell wall
metabolism by product methanol, are released via the stomata in
the morning especially when the stomata open.
• Methylotrophic bacteria belong to the genus Methylobacterium are
known to metabolize methanol.
• Soil or foliar application of Methylobacterium colonize the plant and
interact with the endophytic microbial community in turn
preventing the crops from adverse temperature fluctuations.
• Methylobacterium is believed to be involved in drought resistance
and induced systemic resistance.

41. Green Plus(Methylobacterium)
• Dosage : 3 Liters / ha
• Shelf Life : One Year
• Packing: 500ml,1 Litre, 5 Litres
• Method of Application:
 Seed Treatment: Mix 10 ml of Green Plus with 1 kg of seeds and
moisturize with cooled rice gruel or water and leave it for 30
minutes and sow the seeds.
 Seedling Root dipping: The seedlings in pouch or tray can be
treated with 1% Green Plus solution (10 ml /litre of water). The
root of seedlings should be placed in 1 % Green Plus solution
for at least 10 minutes before plantation. Prolonged dipping or
soaking is acceptable and it will enhance the ef ciency.
 Soil application: 500 ml of Green Plus is recommended per
acre. Mix the desired volume with 50 – 100 kg of farmyard
manure or sand and broadcast in the eld. For ef ciency, mix
the Green Plus with farmyard manure and leave it for few days
and broadcast it in the eld before sowing or transplantation.
The Green Plus can also be applied through drip irrigation.
• Spray: Foliar and bunch spray can be done. Spray the Green
Plus at 1 % concentration (10ml/litre of water) at regular
interval of 1 month after transplantation.
• Content: Methylobacterium (2 x 109 cfu / ml)
• Caution: Do not mix with chemical fungicides or fertilizers.

42. Table: Some of the microbes that confer abiotic stress
MICRO ORGANISMS ABIOTIC STRESS HOST PLANT
Neotyphodium sps Drought Fetuca pratensis
F. arizonica
Tail fescue
Curvularia protuberate Drought Triticum aestivum
Watermelon
Curvularia sps Heat Dichanthelium lanuginosum
P. fluorescens Salt Groundnut, maize
Azospirullum Salt
Drought
Lettuce
Wheat
Bacillus species Iron toxicity Maize
Serratia liquifaciens Temperature Soyabean
Aeromonas hydrophila Temperature
Salt
Soya bean
Wheat
Enterobacter aerogenes Salt Maize
Bacillus species Drought Lettuce

43. MICRO ORGANISMS ABIOTIC STRESS HOST PLANT
Arthrobacter piechaudii Drought Tomato , pepper, wheat
P.syringae Salt Maize
Burkholderia phytofirmans Temperature Grapevine
Arthrobacter sps Osmotic stress pepper
P. indica Drought Brassica campestris ssp. Chinensis
Fusarium sp. Heat/Drought L. esculentum
P. indica Drought Arabidopsis sp.
Trichoderma hamatum (DIS 219b) Drought Theobroma cacao

44. CONCLUSION
• Microorganisms, the most natural inhabitants of diverse environments exhibit
enormous metabolic capabilities to mitigate abiotic stresses.
• Several studies have reported that soil microorganisms may have mechanisms for
alleviation of abiotic stresses in plants such as water and temperature stress, salinity,
heavy metals etc.
• Furthermore since microbial interactions with plants are an integral part of the living
ecosystem, they are believed to be the natural partners that modulate local and
systemic mechanisms in plants to offer defense under adverse external conditions.
• Induced Systemic Tolerance (IST) is the term being used for microbe-mediated
induction of abiotic stress responses. The role of microorganisms to alleviate abiotic
stresses in plants has been the area of great concern in past few decades.
• Microbes mediated stress tolerance in plants is an ecofriendly approach for crop yield.
It can increase the crop land and species diversity.
• Plants in symbiosis with microbes have an improved ability for nutrient acquisition
and exhibit enhanced tolerance to different stresses while the fungus acquires a
protected ecological niche and plant photosynthates (Smith and Read, 2008).

45. REFERENCES
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abiotic stress tolerance; Plant Signaling & Behavior 6:2, 175-191.
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RESS_TOLERANCE_IN_PLANTS_BY_ENDOPHYTIC_MICROBES
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• https://link.springer.com/article/10.1007%2Fs00299-018-2341-2
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