about wheat blast an emerging threat to wheat production

1. Wheat blast : An emerging threat to wheat
production
Wheat blast : An emerging threat to wheat
production

2. Wheat Facts
• Worldwide: Most important food grain over 220 m . hectares
• Uses : Human food: bread, noodle, pasta
Fermented products: beer, alcohol
Construction materials: roof thatch
Live stock feed: grain, straw
• Nutritional: Carbohydrates, protien, minerals, vitamins
• 20%food calorie for the world
• Classes : Ploidy level: tertaploid/hexaploid
Growth habit: winter/spring/facultative
Kernel hardness: soft/hard
Kernel color: red/ white

3. Wheat production(million metric tons)
Country/group 2011-12 2012-13 2013-14 2014-15 2015-2016
1.China 117.4 121.0 121.9 126.2 130.0
2.India 86.9 94.9 93.5 95.8 88.9
3.Russia 56.2 37.7 52.1 59.1 61.0
4.USA 54.2 61.3 58.1 55.1 55.8
5.EU(France) 138.2(40) 133.9(39) 144.4(38) 156.5(39) 154.1
6.Canada 25.3 27.2 37.5 29.4 26
7.Australia 29.9 2209 25.3 23.7 26
World produce 696.1 658.7 715.1 725.5 732.8
World use 697.5 679.2 698.5 707.2 716.4
Source: USDA-FAS

4. 75%of all farmers live in Asia

5.  Discovered in Parana state of
Brazil in 1985 and since then
spreading to an area of about 3.0
mha causing losses of 10-100%.
 Reported in central and south
Brazil, Bolivia, NE Argentina, S &
SE Paraguay And Uruguay
Observed in Kentucky in 2011,
vigorous surveillance helped stop
spreading in U.S.A
Observed in Bangladesh in 2016
WHEAT
BLAST
2016

7. Comparison of two Blast diseases
• Found in all rice growing regions
• Still often controlled by fungicides
• >85 major resistance genes identified, 18
of these are cloned
• Only asexual reproduction in most of the
world
• Symptoms on young expanded leaves
• A potential threat to global wheat production
• Control with fungicides unreliable
• Few resistance genes identified
• Mixed reproduction sexual followed by asexual
(brazil-before 1980, Himalayan foothills of India ,
china , late 1980s onwards asexual)
•Symptoms on oldest leaves

8. CAuSAL
orgAniSm
• Initially thought to be P. oryzae and some author named
as Triticum isolates of P. oryzae. Sprague (1950)
• Later Kohli et al. preferred name as Pyricularia grisea.
• Using multilocus phylogenetic analysis Couch and
Kuhn(2002) described P. oryzae distinct from P. grisea
•Recently Castroagudin et al. (2016) conducted phylogenetic assays on
different isolates of P. oryzae from sympatric populations of grasses
growing in or near wheat fields, so based on clades they conclude P. oryzae
pathotype Triticum to be the pathogen responsible for wheat blast.
Fig. Two septate pyriform conidia of
Pyriculariaon
wheat
Urashima et al .,

9. Domain: Eukaryota
Kingdom: Fungi
Phylum: Ascomycota
Subphylum: Pezizomycotina
Class: Sordariomycetes
Subclass: Sordariomycetidae
Family: Magnaporthaceae
Genus: Magnaporthe
Species: Magnaporthe oryzae
Triticum pathotype
Taxonomic Tree: Can infect 50 grasses
Hemibiotroph
Pyriform conidia
Grey colour
3 types of conidia
Can infect 50 grasses
Hemibiotroph
Pyriform conidia
Grey colour
3 types of conidia
Asexual pyriform conidia,
Asexual microconidia
produced from phialides
Depiction
of perithecia and ascospores

10. Pyricularia oryzae is a species complex (Couch & Kuhn 2002).
Cause blast in more than 50 species of poaceous plants.
E.g.: Oryza pathotype, pathogenic on rice
Setaria pathotype, pathogenic on foxtail millet
Eleusine pathotype, pathogenic on finger millet and
Triticum pathotype, pathogenic on wheat (Urashima et al ., 1998)

11. Pathogenicity spectra of Pyricularia graminis-tritici (Pgt) and P. oryzae pathotypes
Triticum (PoT) and Oryza (PoO)
Castroagudin et al. (2016)
Wheat blast isolates from Pgt or PoT do not infect rice, but they all infect
barley, oat and signal grass
Rice blast isolates (PoO) infect barley, oat, and wheat, but not signal grass.
Barley Oat Signal grass Wheat Rice
Pgt + + + + -
PoT + + + + -
(clades 1 and 2)
PoO + + - + +
The hypothesis of ”host-specific forms” does not hold for
the wheat blast pathogens.
The hypothesis of ”host-specific forms” does not hold for
the wheat blast pathogens.

12.  Infects all above ground parts of plant.
 On leaves lesions vary in shape and size
depending on the stage of plants.
As plants grow older, lesions are less
frequent.
Lesions with white centre and of reddish
brown margin on upper side, dark grey on the
underside of the leaf can be observed on both
young and old infected leaves.
 Resemblance to Fusarium head blight
Major symptom on head/spike infection.
Symptomatology
Mahendra singh et al.,2016

13. Occurs on the glumes, awns and
rachis.
-Blackening of the rachis, lower
nodes, shriveling of grains, low test
weight has also been observed
- Infected glumes support elliptical
lesions with reddish brown to dark
grey margins and white to light
brown centre.
-The pathogen produce non host
specific toxin pyricularin .
- Infecting place on head determine
partial or full head drying. (Agrios, 2005) Malaker et al., 2016)

14. Conidia produced by different pathotypes of Pyricularia

15. High Degree 0f Host Specificity

16. HOST RECOGNIZATION AND PENETRATION BY MoO

17. MoT infection and disease progress curve

18. MoT can be transmitted from spike to seed, and from infected seeds to seedlings.
Estimated rate of MoT transmission from a non-treated seed lot with 21% incidence
could potentially create 400,000 primary inoculum units per hectare
Goulart and Paiva (1990)

19. MoO
MoT
MoL in Lollium

22. Races of Magnoporthe oryzae pathotype Triticum
Race Everest(non
-2NS)
Jagalene(2N
S)
Ronl(non-
2NS)
0 R R R
1 S R R
2 S R S
3 S S S
EARLY STRAINS
FROM BRAZIL,
LATE 1980’S (T-28)
RECENT STRAINS
FROM
BOLIVIA & BRAZIL,
2012 (B-71)

23. Scoring of wheat blast incidence at seedling stage is done on the scale of 0 to 9
0 - no lesions (highly resistant);
1 - small, brown,specks of pinhead size;
2 - small roundish to slightly elongated, necrotic gray spots, about 1-2 mm in dia, with a distinct brown
margin
3- small, roundish, elongated, necrotic gray spots (1-2 mm in diameter)
4- 3 mm or more infecting less than 4% of leaf area.
5- was for typical blast lesions infecting <10% leaf area,
6- 3 mm or longer infecting 11- 25% of the leaf area
7 - blighted area of leaf in the range of 26-50%
8 - lesions of 3 mm or more with infected area from 51 to 75% of the leaf with few dead leaves
9 - >51% leaf area infected along with many dead leaves.
0-1 - resistant reaction,
2-3 for moderately resistant,
4-5 for moderately susceptible,
6-7 for susceptible and
8-9 for the highly susceptible category IRRI, 1996
Rating scales

24. • Most severe blast years coincide with wet years
• Continuous rains and average temperatures between 18-20°C during the flowering stage of
the crop followed by sunny host and humid days.
• Under controlled conditions highest blast intensity at 30°C was observed with duration of
wetting period
• lowest at 25°C with a wetting period of < 10h.
• However, with increasing wetting period of 40h at 25°C blast intensity of 85% was
observed.
• Sprinkler irrigation may expose the plants to blast. Global temperature rise may predispose
wheat to blast.
• Saprophytic growth and conidial production in basal senescent leaves coincide with spike
emergence Kohl i et al., (2011)

25. • Production losses caused by Pyricularia blast can vary from very low to 100% (Goulart and
Paiva, 1990; Goulart et al.1992).
• First epidemic in Paraguay caused more than 70% losses (Viedma and Morel, 2002).
• Infection in low lands of Santa Cruz region of Bolivia in 1996 resulted in 80% yield
reduction in wheat (Barca and Toledo,1996).
• Government owned blast infected fields were burnt in Bangladesh
World wide production lossesWorld wide production losses
BRAZIL BOLIVIA
Mahendra singh et al.,2016

26. Host Resistance (not clear due to tricky and variable pathogen)
• The first AVR-type gene cloned from M. oryzae, named PWL2, was a host species specificity
gene that prevents strains that carry it from infecting weeping lovegrass (Eragrostis curvula)
• Five AVR effector-like genes (PWT1–5) from Oryza, Setaria and Avena isolates
independently block infection of wheat .
• Tosa and colleagues genetically confirmed a gene-for-gene relationship responsible for
incompatibility of a Lolium isolate on wheat
• They identified two gene pairs that block infection of wheat:
I. MoL AVR gene A1 and its corresponding wheat R gene Rmg6 conferring strong resistance.
II. the AVR gene A2 and its corresponding R gene R2 conferring weak resistance.
• An additional wheat R gene Rmg1 blocks Avena isolates from infecting wheat.
• Two wheat genes, Rmg4 and Rmg5, independently block Digitaria isolates from infecting
wheat
(Tosa et al. 2006).

27.  Studies of 27 wheat cultivars with two ear pathogens Magnaporthe wheat blast (WB) and Fusarium
head blight (FHB) revealed that most of the 27 cultivars displayed inverse disease response to two
diseases.
 The cultivar ‘Milan’ (CIMMYT) displayed resistance (R) to blast and susceptible (S) to FHB
 Note that wheat leaf rust resistance gene Lr34 confers resistance to blast in rice but not for WB.
 Brazilian cultivars: BR18, IRR85, CD113- moderately resistant
 Everest, karl 92- susceptible
 Post rock, jack pot, overley, jaglene jagger - <3% infection
 Limited QTL linked residence genes available
Host jump: ( USA, 2011)
• Host shifts and emergence of new diseases like wheat blast could easily result from loss of a few AVR
genes
• Rice blast disease caused by the MoO population appears to have arisen from a host jump from
Setaria pathogens around the time rice was domesticated ~7000 years Ago
• The wheat pathogen in Brazil was originally suggested to have jumped from rice or Urochloa( from
Africa to Brazil) because blast was endemic in rice produced in northern Paraná state in 1985.
Cruz et al. (2016)

28. Management
Host resistance: R genes
• Cruz identified a WHB resistance trait contained on a wild wheat chromosome segment (the
2NS translocation segment from Aegilops ventricosa).
• Field tests in Bolivia in 2014 and 2015 confirmed that the 2NS segment confers head blast
resistance under natural epidemic conditions.
• ( fragment which incorporated into diverse cultivated wheat varieties due to its useful rust
and nematode R genes)
Cultural:
• Avoid heading to coincide with increasing temperature, high precipitation, high RH
• Deep ploughing .
Cruz et al. (2016)

29. Chemical: ( can reduced MoT sporulation from 52.2 to 100%)
• Silicon application ,
• Seed treatment
• Fungicide : only effective in flag leaf stage
• Widespread fungicide resistance would limit fungicide efficacy.
• Extensive use of strobilurin (QoI) fungicides in Brazil has led to widespread distribution of cyt
b mutations conferring resistance in strains isolated from wheat and other grasses
• Several substances like jasmonic acid (JA), deacetylated chitosan (DC), potassium silicate
(PS), potassium phosphate (PP), tebuconazole (TE) tricyclazole, thiophanate-methyl+
mancozeb are tested against WB
• Biological control: The methanol extract from stems of a tree of Chinese origin, Catalpa
ovata Trichoderma harzianum Pseudomonas spp. and Bacillus spp.
Cruz et al. (2016)

30. Why should we be concerned about blast disease?
• The causative agent, a fungus, Magnaporthe oryzae, strikes directly to wither and
deform wheat grains, leaving farmers with no time to act.
• The new Bangladesh MoT strain is much more aggressive than earlier strains
• Wheat blast can spread easily via commercial grain shipments or farmer-to-farmer
seed exchanges as it is seed-borne.
• The conidia, that have the capability of causing disease, can be blown over long
distances across farms and borders
• Fungicides provide partial defense, and must be applied before symptoms appear

31. • Outbreaks are occasional and difficult to predict
• The fungus can grow on other cereal crops that include barley, maize, oat and foxtail millet
• Wheat blast can reduce wheat yields from 10 to 100% depending on genotype, planting time,
rainfall and disease severity
• The pathogen evolves rapidly, making it difficult to develop a wheat cultivar with durable
resistance
• With porous borders in the South Asian countries, the disease assumes more significance as
probability of cross-border movement of pathogen become high
Why should we be concerned about blast disease?

32. Recent spread in
Bangladesh
• On Feb, 2016 outbreak was reported in Bangladesh. (Callaway, 2016; Malaker et
al., 2016)
• Affected in 15000 hectares with resultant fall in production by 20%. (Malaker et
al., 2016) Extant 15% wheat area been observed under disease.
Islam et al .,
2016

33. 0
10
20
30
40
50
60
70
80
M C J
E
JH BH K BA P
% INFECTED
FIELD AVG.
YIELD LOSS
The severity of wheat blast and associated yield losses varied among districts.
Islam et al ., 2016

34. Economic importance of wheat in Bangladesh
The wheat blast strains might be migrated from South America to Bangladesh via
man-made transport. A local newspaper also reported that the seeds imported from
Brazil in 2015 for the consumption purpose were seen as unhealthy

37. • BLAST RESISTENCE IN BANGLADESH
1st
blast resistant, biofortified wheat variety released in Bangladesh
• NSB released a new variety “ BARI Gom33”(Gom -wheat grain) which is developed by WRC using
breeding line from CIMMYT.
• They proposed a new project with AROB, including (BARI), and institutions in Bolivia, other
partners national and provincial research organizations in India, Nepal and Pakistan, (USDA-ARS).
• BARI Gom33 features 30 percent higher levels of zinc than conventional wheat.
• leading international donors and scientists, nine South Asia wheat researchers recently visited the
Americas for training on measures to control a deadly and mysterious South American wheat disease
that appeared suddenly on their doorstep in 2016
• CIMMYT conducted the workshops , where all India, Nepal, Bangladesh, Mexico researchers
taking from lab to field in Bolivia .
• Bangladesh also conducted workshop in 2017 for giving training to researchers.

38. Short term :
• 1- Educate farmers and relevant stakeholders
• 2- Procurement of quality seeds produced in disease free area for planting in 2016-17 season.
• 3- Evaluation of wheat blast resistance in wheat varieties and gerrnplasrn
• 4. Fast track seed multiplication of less infected/tolerant varieties.
Medium Term
• 1. Multi-location testing of gerrnplasm.
• 2. Explore agronomic interventions like time of planting, seed treatment. stubble management, crop
diversification etc.
• 3. Fast track seed multiplication engaging private sector
Long Term
• 1_ Breeding and testing of blast resistant varieties.
• 2. Participatory Variety Selection and cesp.
Others:
• Seed treatment with Tebuconazole (reduce infection in 2016-17
• Crop rotation with non-cereal crops like sesame, Mungbean, Sesbania
• Foliar spray with Nativo (Tebuconazole+ Trifloxystrobin) or Folicur(Tebuconazole)
Managing strategies in Bangladesh

39. Reasons of concern in Indian conditions
• Epidemiology of disease largely unknown
• Disease cycle and survival of the pathogen is unknown
• Resistance is largely in effective and no enough research on fungicides
• Although seed transmitted disease, germplasm and seed exchange may initiate disease for
the disease
• Environmental conditions of North Eastern Plains of India are favorable for entry and
establishment of pathogen from Bangladesh
Reasons of concern in Indian conditions
• Epidemiology of disease largely unknown
• Disease cycle and survival of the pathogen is unknown
• Resistance is largely in effective and no enough research on fungicides
• Although seed transmitted disease, germplasm and seed exchange may initiate disease for
the disease
• Environmental conditions of North Eastern Plains of India are favorable for entry and
establishment of pathogen from Bangladesh

40. IN INDIA
• Minutes of meeting on “Occurrence of blast disease on wheat” held under Chairmanship
of Agriculture Commissioner on 28th
September, 2016 at Kolkata.
• Participants are where from DAC&FW, ICAR, Tripura, Assam, Meghalaya and West
Bengal state Agriculture department.
• They discussed about our states lie Tripura, Assam, Meghalaya and West Bengal which have
porous border with 6 states of Bangladesh which are most severally affected (15000ha area).
• No confirmed symptoms of WB , mostly appears as boron deficiency.
• Need to have a road map to tackle this disease.
• Conducted survey in border area in WB ( North 24 Parganas, Nadia, Murshidabad and Malda
districts), not find any symptoms
• Need to destroy the alternate host, giving fungicide application

41. • Follow short term strategy like scouting , fungicide and weedicide application to control
early infection
• Bangladesh farmers have 80 % seed , which can be a potential risk
• Need of international project for Bangladesh for research facilities on managing disease
• No imports, Domestic quarantine
• Action taken by ICAR-IIWBR : Through zonal monitoring teams surveyed six centers in
WB9 and 3 centers in Assam Dhubri, Chirang and Shillongani)
• Not found the disease but only spot blotch was obsereved
• Evalution of Indian varieties against blast:
• They informed that we have sent 40 genotypes to Bolivia for screening under ICAR-
CIMMYT in 2016 Work plan against the disease , so that sources of resistance can be
identified.
• Mentioned about two CIMMYT derived Mexican varieties Roelfs F2007, Borlaug 100F2014
and breeding line Supper 152/Baj1 (moderately resistant)

42. • SOFTCORE AREAS OF INDIA TO WHEAT BLAST in India
• ASSAM:
• Districts like Cachar, Hailkandi, Golapara and Dhubri vulnerable to WB attack.
• varieties used are Sonalika, Molla, Bhutia, Barpetia.
• TRIPURA:
• Hot and humid conditions in kharif and Pre-kharif seasons matching with Bangladesh.
• Chances of entry through Sepahijala district
• Need to strengthen the phytosanitary set up in kailashahar, South Tripura , North Tripura and
Agartala.
• MEGHALAYA: no area under wheat
• WESTBENGAL:
• 49 blocks of eight districts namely Cooch behar, Jalpaiguri, Dakshin Dinajpur, Uttar Dinajpur,
Malda, Murshidbad, Nadia And North 24 Paranas are .vulnerable to wheat blast

43. Strategies for management of wheat blast in India:
Avoid cultivation of wheat in the border area adjoining Bangladesh, impose strict Quarantine
measures, undertake Survey and MoT Spore surveillance, follow Chemical control and use of
resistant varieties.
Not to grow wheat along with Indo-Bangladesh boarders and follow Prophylactic sprays of
fungicides on collateral hosts
 Avoiding bulk purchase of wheat grains and seeds from affected countries where wheat blast
occurs.
 Follow strict seed health testing for MoTriticum and other blast causing pathogens in wheat.
Local quarantine in case wheat blast is reported from any part of India. Strict prevention of entry
of wheat grains, wheat plant parts and persons/animals in India from Bangladesh wheat fields
directly to wheat fields in India.
Strategies for management of wheat blast in India:
Avoid cultivation of wheat in the border area adjoining Bangladesh, impose strict Quarantine
measures, undertake Survey and MoT Spore surveillance, follow Chemical control and use of
resistant varieties.
Not to grow wheat along with Indo-Bangladesh boarders and follow Prophylactic sprays of
fungicides on collateral hosts
 Avoiding bulk purchase of wheat grains and seeds from affected countries where wheat blast
occurs.
 Follow strict seed health testing for MoTriticum and other blast causing pathogens in wheat.
Local quarantine in case wheat blast is reported from any part of India. Strict prevention of entry
of wheat grains, wheat plant parts and persons/animals in India from Bangladesh wheat fields
directly to wheat fields in India.

44. Monitoring of wheat crop at Bangladesh borders through visits, monitoring nurseries
and using IT tools.
 Training of field extension officers and farmers in identification of wheat blast and other
diseases of wheat.
Sampling and analysis of blighted leaf and panicle of wheat
Seed Treatment: Carboxin 20%+Thiram 20%, Benomyl and carberidazirn+thiram@
200 mg/ 100 kg seed. Carbendazim (50g a.i/100kg seed), Mancozeb (160g a.i/100kg seed).
Foliar and panicle sprays: triazols with strobilurins, tebuconazole (600ml/ha),
trifloxystrobin 10% + tebuconazole 20% at 3 kg a.i./ ha

45. Areas Vulnerable To Wheat Blast In Bangladesh, India, PakistanAreas Vulnerable To Wheat Blast In Bangladesh, India, Pakistan
LONG TERM STRATEGIES :

46. Wheat Blast Collaboration For Success

47. Although the wheat blast has not been reported in India, it is still a question
of national food security for India and is an emergency as it could have
global implications.
It is the need of the hour for the Indian government and all wheat
stakeholders, both in India and the globe, to be proactive and put forward an
integrated solution to prevent this enemy from expanding its presence and
making an entry into India and the region!!
Although the wheat blast has not been reported in India, it is still a question
of national food security for India and is an emergency as it could have
global implications.
It is the need of the hour for the Indian government and all wheat
stakeholders, both in India and the globe, to be proactive and put forward an
integrated solution to prevent this enemy from expanding its presence and
making an entry into India and the region!!
Conclusion:

48. Future challenges
• Challenges for wheat blast include the scarcity of identified R genes in wheat.
• Need to test lines with non-2NS resistance under natural epidemic conditions .
• Transgenic and genome-editing strategies based on the detailed understanding of the fungal infection
process and wheat resistance mechanisms could provide longer-term solutions.
• Development of effective and integrated management strategies
• Research on the ecology of M. oryzae pathotypes that threaten wheat.
• Research is needed to identify the main source(s) of inoculum in the field.
• It is critical to define incubation and latent periods, optimum plant growth stages for infection, and critical
microclimate details.
• Remote sensing, “ground truth”, and molecular diagnostics methods will be necessary to determine if
MoT seedborne inoculum is epidemiologically important
• Better surveillance systems, preparedness infrastructure, prevention and control tools must be developed,
especially in countries at risk.

49. References:
• Castroagudin VL et al. 2015. Resistance to QoI fungicides is widespread in Brazilian populations of the wheat
blast pathogen Magnaporthe oryzae. Phytopathology.104:284–94.
• Christian D. Cruz and Barbara Valent.2017.Wheat blast disease: danger on the move. Trop. plant pathol. 42:210–
222
• Kohli, M, Y Mehta, E Guzman, L Viedma and L Cubilla. 2011. Pyricularia blast – A threat to wheat cultivation.
Czech J. Genet. Plant Breed. 47:130-134.
• Mahender Singh Saharan. 2016. Wheat blast disease - An overview. Journal of Wheat Research. 8(1):1-5
• Md. Abu Sadat and Jaehyuk Choi.2017. Wheat Blast: A New Fungal Inhabitant to Bangladesh Threatening
World Wheat Production . Plant Pathol. J. 33(2) : 103-108
• M. Tofazzal Islam et al.2016.Emergence of wheat blast in Bangladesh was caused by a South American lineage
of Magnaporthe oryzae. BMC Biology .14:84
• Rajiv Sharma.2017. Wheat blast research: Status and imperatives. African Journal of Agricultural Reseacrch.
Vol. 12(6), pp. 377-381
• CIMMYT(2016).WheatBlast. Retrieved fromhttp://www.cimmyt.org/wheat-blast

50. Major losses to wheat blast in South Asia and beyond can be
avoided if an integrated control strategy is implemented
urgently
Do not forget