DEPARTMENT OF P. G. STUDIES AND RESEARCH IN APPLIED BOTANY
Jnana Sahyadri, SHANKARAGHATTA – 577 451
A Dissertation Entitled
DIVERSITY OF PYRICULARIA ORYZAE
CAVARA. ON PADDY CROPS IN SHIMOGA
Mr. CHANDRASHEKAR, D.G.
Prof. M. KRISHNAPPA
2. REVIEW OF LITERATURE
3. AIMS AND OBJECTIVES
4. CONTROL AND MANAGEMENT OF BLAST
5. MATERIALS AND METHODS
6. RESULTS AND DISCUSSION
Rice (Oryza sativa L.) is one of the most important crops of the world
both in terms of area (152 mha) and production (585.6 mt) and major food
crop for Asia. Rice is not only a major staple but also exports commodity
since last ten years (Siddiq, 2002). Sixty percent of world population
depends on paddy, the byproduct of rice milling rice husk and bran are
used a cattle and poultry feed. Rice is main food source for more than 60
per cent population in the country. Chhattisgarh is famous as ‘Rice Bowl’
Origin of Rice
Archaeologists of India have found charred grains of rice in
Mohenjodaro of ancient Indus civilization. Apart from it, rice grains
dating back to 2000 B.C. has been found in excavations of Lothal and
Rangpur in Gujarat. Rice grains were also obtained at archeological sites
of Japan, China, Korea and Thailand indicating its culture in ancient era.
However rice is not mentioned in Bible. Evidence indicates that it was
cultivated in Nile Valley around AD 640. Alexander, the great Greek
Conqueror brought rice from India during his invasions. His teacher and
Philosopher, Aristotle called the rice as Oryzon and mentioned in his
botanical records. Thus rice was introduced first in Europe by Alexander.
Indicia rice’s were carried by seafaring traders to Malaya and Java and
later to Sri Lanka in 543 B.C.
Table 1. Major pathogens of paddy
Disease Causal organism Symptoms
Country from which
disease was first
Pyricularia oryzae. Cavara Leaf spot, leaf blast, neck
Brown spot Drechslera oryzae /
Seedling, bright brown,
leaf spot, leaf blight,
sesame spot pecky rice,
black sheath rot
Bunt Tilletia horridea Tak. Sticky spores, stunted
Claviceps oryzae sativa
Grains into large green
Ephelis oryzae Syd. Incense stick like
panicles, black ring
Stack burn Trichococomis padwickii Stack burn, seedling
blight, pnk kernel, leaf
Louisiana and Texas
Leaf smut Entyloma oryzae Leaden black coloured
Bacterial leaf blight
Closon pv. oryzae.
Small water soaked
Tungro disease Rice tungro virus Syn. Interveinal chlorosis
Ufra disease Ditylenchus angustus Buttler. Withering and death
White tip Aphelenchoides besseyi Infected seeds,
nematodes lie in
beneath half of the
Table 2. Details of paddy production in Karnataka
YearYear Production (in million tonnes)Production (in million tonnes)
Source : http: //raitamitra.kar.nic.in.statistics.html
In Karnataka, paddy is grown in Shimoga, Chikmagalur,
Chitradurga, Raichur, Mandya, Dakshina Kannada, Belgaum and
Mysore which occupies 14.83 lakh hectares. Among that 10.71
lakh hectares of irrigated and 4.12 lakh hectares under rainfed
condition. The annual production amount 38.47 lakh tonnes in the
year 2000-01 accounts an average of 2520 kg/hectare.
Karnataka stands 5th
position in paddy production followed by
Tamil Nadu, Andhra Pradesh, Maharashtra and overall India.
Rainfall plays an important role in getting good yield and also in
blast development. Heavy rainfall and relative humidity ≥ 90%
influences blast at high rate (Kapoor, 2002).
Shimoga district had an total geographic area of
8,47,784 hectares comprising 2,76, 855 hectares of forest,
1,01,605 hectares under non agricultural usage and remaining
4,69,324 hectares under cultivation of various crops. A total
rainfall of 1703 mm is recorded between May to October months
of 2006. The district paddy occupies 1,33,436 hectares
comprising 28.43% of land under cultivation (Statistical
Department, DC Office, Shimoga).
Origin of Pyricularia oryzae
Pyricularia oryzae causal organism of leaf spot, leaf
blast and neck blast symptoms and is first reported from
Italy (Cavara, 1891 and Gangopadhyay, 1983). Rice blast
occurs in 80 rice growing countries causing considerable
yield reduction. The disease is believed to have occurred in
Japan as early as 1704. The causal organism was however
identified almost 200 years later in Italy in 1891. In India
the disease was first reported in Tanjavore district in
Nearly 30 fungal diseases affect rice in India of
these blast is one of the most significant diseases since
crop damage can be as high as 70-80%.
Fig. 2. Mode of infection
A - Attachment of Conidia to
the plant surface
B - Germination of conidium by
sending out a short germ tube.
The apical end of the germ
tube extends and form a ‘Hook’
C - Formation of nascent
D - Melanin layer forms in the
appressorial cellwall during the
maturation of infectious stage
E - Driven by turgor pressure
peg is forced through the plant
cuticle to infect leaf
F - Formation of intracellular
G - Spread of the infection
followed by conidiation
Map 3. Shimoga district Land use / Land cover map
REVIEW OF LITERATURE
Vijaya and Balasubramaniyan (2002) reported the significant
difference among the dates of sowing in both the years (1996 and
1997) of experimentation for PDI (percent disease incidence) and grain
yield maximum reduction in diseases incidence was observed, when the
crop was transplanted on 27th July from the nurseries of early on
30th June followed by the nursery sow on 15th July. Maximum grain
yield was obtained from the crop grown with the nursery sown on 30th
Kapoor et al. (2002) have analyzed 13 years (1984-1996) weather
data revealed that the number of days with RH of ≥ 90% (47 and 27
days) during July to September, number of rainy days in a week and
cloudiness was most critical factor in the development of rice blast
epidemics during blast years of 1984 and 1992.
Misra et al. (1997) have found the essential oil of Callistemon
lanceolatus recorded, inhibitory activity against the germination of
Magnoporthe grisea at 3000 ppm. The mycelial growth was however
completely inhibited by only at 8000 ppm, nevertheless, 8000 ppm
registered complete inhibition for specifically to stored grain
pathogens of rice.
AIMS AND OBJECTIVES
Survey and collection of paddy blast diseased
Cultural characteristics and conidial diversity of
Pyricularia oryzae Cavara. in Shimoga district.
Pathogenicity study of Pyricularia oryzae on host
CONTROL AND MANAGEMENT OF
In the present day fungicides play an important role in
disease management, most of the early fungicides with low
biochemical specificity. The fungicides are usually inorganic
chemical constituents like copper oxychloride, aretan, ceresan,
hinosan, kasumin, deuter, brestanol, organomercuric and organo
sulphuric derivatives were least effective in control of the blast.
Gangawane (1997) found Kitazin-P is effective fungicide
for P. oryzae. Dubey (1997) found Tricyclazole efficacy against
blast was superior over the control of neck and node infection.
Vidyasekaran et al. (1997) developed powder formulation of
Pseudomonas fluorescence for control of blast. In test a seed
treatment and foliar spray in four field trials is effectively
control the disease and increased grain yield.
Chakraborty and Rao (1990) eliminated seed borne
pathogens including P. oryzae by mandatory quarantine hot water
treatment of 54°C for 30 min. with 6 h spore soaking was tried
against naturally infected seeds.
MATERIALS AND METHODS
1. Survey and Collection of Paddy Blast Material
Shimoga is one of the twenty seven revenue
district of Karnataka state in India. It is situated in the
midsouth western part of the state. The district is
situated between 13° 27" and 14° 39" N latitude and
between 74° 38" and 76° 4" E longitude. The
geographical area of the district as per survey of India
8439.3 sq.kms. Shimoga district divided into seven
revenue administrative bodies called taluks, viz.,
Bhadravathi, Hosnagar, Sagar, Sorab, Shikaripur,
Shimoga and Thirthahalli.
The Shimoga district clearly divided into two equal parts
depending upon physiographic factors. The eastern part of the
district comprises of Bhadravathi, Shimoga and part of Shikaripur
taluk. This region generally known as Maidan(plane land) and
absence of rich forest. The western part of the district having
Thirthahalli, Sagar, Sorab, Hosanagar and part of Shikaripur taluk
known as malnad (hilly tract), this region lies in the part of
Western Ghats of this region having moist, ever green forest belt.
The district slopes from west to east. The general elevation is
529 to 640 MSL.
2.Isolation of P. oryzae from Diseased Material
Before isolating a fungal pathogen from diseased material,
the tissue should be examined for fruiting bodies and mycelium.
Most of fungal pathogens attacking aerial parts of the plant body
readily sporulate on the host, if kept moist at a suitable
temperature, making isolation of pathogen easier. If spores are
present on the diseased surface, a few spores may be shaken
loose over a Petri plate containing wet blotter (Aneja, 2007).
Standard Blotter Method
The blotter method is used widely, since it is simple
and inexpensive means of detecting pathogens of leaves
for fungi, which readily form mycelial growth on leaves.
This method provides optimum conditions for a number of
fungi. The disease infected rice leaf discs were plated on
two layers of moist blotter discs kept in 9 cm plastic
petridishes at equidistant, that each plate contains 5 to 8
discs, these plates were incubated for 5 days under
12h/12h under normal lab conditions. The occurrence of
associated mycoflora with P. oryzae were identified on
fifth day using stereo-binocular microscope (Agarwal and
Preparation of potato dextrose agar
Method of inoculation
For this purpose, following procedures are adopted,
Agar plant culture of the pathogen is selected out and
take freshly sterilized culture medium, in which culture is
to be inoculated.
To the sterilized media a pinch of antibiotic was
added to avoid the bacterial contamination and it was
poured into the sterilized glass petriplates.
After solidifying of the media, the P. oryzae
culture present on the incubated leaf material was taken
in a needle and it was inoculated into the centre of the
petriplate near the flame.
All these procedures are done in aseptic condition
in the laminar air flow chamber.
Inoculated petriplates were incubated in a
incubation chamber at 20 to 40°C for 5 to 7 days.
3. Pathogenicity Study of P. oryzae on Host Plant
Phylloplane is a natural habitat on leaf surface
which supports heterogenous population comprising
both pathogens and non pathogens. There are two
1. Serial dilution plate method and
2. Leaf impression method
Here serial dilution plate method was conducted
to confirm the pathogenicity test.
Table 3. Land use pattern of the study area during
Kharif season (June to October), 2007
TalukTaluk Area of cultivationArea of cultivation PaddyPaddy Forest (inForest (in
BhadravathiBhadravathi 42,55142,551 20,97220,972 18,23918,239
HosnagarHosnagar 17,87317,873 12,24612,246 35,02735,027
SagarSagar 26,26126,261 16,54816,548 66,12566,125
ShikaripurShikaripur 49,97249,972 31,15331,153 40,17340,173
ShimogaShimoga 45,33845,338 23,83423,834 42,89242,892
SorabaSoraba 44,69944,699 30,68430,684 26,66726,667
ThirthalliThirthalli 25,67225,672 16,82616,826 47,73747,737
TotalTotal 2,29,7332,29,733 1,52,2631,52,263 2,76,8552,76,855
Table 4. Temperature (in centigrade) and relative
humidity (%) of the study area during kharif season
(June to October), 2007
Temperature (Temperature (°°C)C)
Relative HumidityRelative Humidity
(RH) (%)(RH) (%)
JuneJune 18.0018.00 34.2534.25 94.0094.00
JulyJuly 17.0017.00 32.5032.50 93.5093.50
AugustAugust 16.2516.25 31.7531.75 90.0090.00
SeptemberSeptember 17.5017.50 33.5033.50 92.0092.00
OctoberOctober 17.2517.25 34.5034.50 92.0092.00
NovemberNovember 18.5018.50 30.0030.00 91.5091.50
Table 5. Area of paddy cultivated under
irrigated and rainfed conditions during Kharif
season (June to October), 2007
TalukTaluk Rain fedRain fed IrrigatedIrrigated
BhadarvathiBhadarvathi 3,9523,952 17,02017,020
HosnagarHosnagar 6,2666,266 5,9805,980
SagarSagar 12,80212,802 13,45913,459
ShikaripurShikaripur 11,86611,866 19,28719,287
ShimogaShimoga 7,3917,391 16,44316,443
SorabaSoraba 8,9608,960 21,72421,724
ThitrthalliThitrthalli 3,5883,588 13,23813,238
Source : http://www.shimoga.nic.in.
Table 9. Cultural characters of fourteen isolates of P. oryzae collected from
different geographical regions (Taluks) of Shimoga
Characters P. oryzae isolate
Taluks Bhadravathi Hosnagar Sagar Shikaripur Shimoga Soraba Thirthalli
Colour of Colony
Black Black Black Black Black Black Black
Colony colour Greyish black Greyish
Colony appearance ++ ++++ ++++ ++ +++ ++ +++
Left Left and
Left Right Left Left and
Formation of septum in
the branch near
Indistinct Distinct Distinct Indistinct Distinct Distinct Distinct
Shape of conidia Obclavate Pyriform Pyriform Obclavate Pyriform Obclavate Pyriform
Colour of colony (reverse): Black /White
Colony colour: Blackish grey / Dull White
Colony appearance: ++ Less feathery, +++More feathery , ++++Maximumfeathery
Branching pattern: Right angle / Acute angle
Shape of conidia: Obclavate / Pyriform
Field showing blast symptoms at Hosanagar
Infected blades Infected sheaths Injured blades
PLATE - I
A close view of blast lesion
An enlarged view of blast lesion
PLATE - II
Brown spots Tillers showing brown spots
Sheath with reddish
Early stage symptoms
showing leaf blade yellow
PLATE - III
Appresorium formation in P. oryzae
Characteristic conidia of P. oryzae PDA culture of P. oryzae
Neck blast : Lesions on panicles Spots on rice stalks
PLATE - IV
RESULTS AND DISCUSSION
Paddy (Oryza sativa L.) is the major food crop in the world
today. It is the major agricultural crop growing in 14.82 lakh hectares
in Karnataka with an output of 37.34 million tonnes and also a major
export commodity fetch a foreign exchange of 3,174.15 crores.
South Africa is the major buyer of Indian rice. India ranks second
among major rice growing countries followed by China (Singhal, 2003).
Blast disease is caused by P. oryzae is the most destructive
cause serious losses in yield due to epyphytotics of the disease have
been recorded in different regions. Hosanagar, Sagar and Thirthahalli
has an severe incidence. It has been found to take a heavy toll,
bringing about almost 30 to 50% loss of the crop. It is due to low
night temperatures, hilly malnad climate and heavy rainfall.
Blast made its impact more on kharif paddy than the rabi
paddy. The loss caused due to blast is negligible in rabi. Early records
shows heavy incidence of blast in Shikaripur and Bhadravathi taluks.
Now it was over to malnad part of the district comprising Thirthahalli,
Sagar and Hosanagar taluks. It is rarely occur on panicles resulting in
infertile chaffy grains leading heavy loss to mankind.
In the study area, occurrence of major pathogenic fungus shows
variation in their incidence at different regions due to edaphic
factors. Study area is divided into irrigated and rain fed
conditions. This major pathogenic fungi is more prevalent in rain
fed conditions than irrigated one. In kharif, 2007, the study area
receives an 159 to 1243 mm rainfall, temperature was between 16
to 34°C and relative humidity 89 to 94 % recorded.
The highest annual rainfall recorded in Hosanagar followed by
Thirthahalli and Sagar with 4672, 3805 and 2684 mm respectively.
The economy of the study area is mainly based on agriculture and
66.27% of the cultivable land under paddy cultivation. The paddy
cultivation having two seasons viz., February to May (summer or
rabi) and August to November (rainy or kharif). The paddy having
two cultural practices i.e., under irrigated and rainfed conditions.
The plain land of the study area (Shimoga, Bhadravathi and part of
the Shikaripur taluk) under irrigation having two seasons.
In malnad region (Thirthahalli, Sagar, Sorab, Hosanagar and
part of the Shikaripur taluk) under rainfed condition. Jyothi, Jaya
and Diamond Sona, Ankur Sonum and Sonamasuri are the major
cultivars in the study area. The yield was 2.2 to 2.5 tonnes per
The leaf spot observation in field during the study period
reveals the development of blast epidemics from August to October
was most severe in October or a month before harvest. Since the
disease always prefer to occur at tillering or grain setting stages
resulting in heavy yield loss. 2 to 8 leaf spots per leaf of minimum
1 mm recorded in Bhadravathi and maximum 9 mm recorded in
Hosanagar. The average size of brown spots between 2 to 7.5
The blotter tests screening of pathogenic fungi during a month
before harvesting showed its associated organisms like Penicillium
notatum, Aspergillus niger, Fusarium moniliformae and Cercospora
lunata were observed.
After 5 days of incubation on blotter and pathogenic colony
of organism screened and inoculated on fresh PDA culture, for
cultural characteristics. The cultural plates observed for
cultural characteristics like colony colour (reverse), colony
colour, colony appearance, branching pattern, formation of
septum and shape of conidia among 14 isolates from 7 taluks of
Shimoga district and they are tabulated for their diversity.
Colony characters like types, zonation, shape, colour, diameter
and dry weight’s are tabulated. Among 14 isolates of 7 taluks
of Shimoga district and their diversity would be known.
The spore suspensions of pure culture is injected to healthy
leaf for disease symptoms reveal P. oryzae at 10-4
concentration show similar symptoms to naturally diseased
material is determined. Therefore, pathogenic fungi grow
robustly on 10-4 concentration spore suspension evidenced that
P. oryzae is the causal organism of the paddy blast disease.
Rice production not only boosts for our economy, but also provides
food security to the nation. Our GDP is completely dependent on
agricultural source. Rice is a crop, mainly affected by bacterial, fungal
and viral diseases. But the extent of loss caused by fungal diseases
are high and desirable. Earlier days, blast epidemic was severe in
almost malnad regions. Now it is concentrated over hilly, high rainfall,
humid conditions. Hosanagar, Sagar and Thirthahalli taluks recorded
high blast occurrence, where plain (maidan) region recorded BLB
followed by Udhbatta disease at high extent. Blast can be controlled
by good cultural practices like early sowing to escape or to break life
cycle of blast, proper forecasting methods, uneconomic alternate hosts
(grass species) eliminated by weeding, chemically by the application of
carbendazim and hinosan. By using resistant varieties, more application
of FYM instead of urea, seed treatment with powder formulations of
Pseudomonas fluorescence, hot water treatment at 54°C for 30 min.
with 6 h spore soaking was tried against naturally infected seeds, by
use of eco-friendly based neem based formulations and by using
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