Management of seed borne diseases

1. SUBMITTED TO:
Dr. B. PUSHPAVATHI,
ASSOCIATE PROFESSOR.
SUBMITTED BY:
Mr. K. SAI SANTHOSH
RAM/13-50
SEED SCIENCE AND TECHNOLOGY.

2. 1. Crop production practices
2. Seed treatment
3. Seed certification
4. Plant quarantine

3. For production of quality seed the grower has to follow
some practices like:
 Crop should be maintained & inspected carefully to
produce clean seed.
 Additional care should be ensured for genetic purity,
freedom from diseased & weed seeds, etc.
 Seed crop should be grown in regions with minimum
disease pressure.
 Disease resistant varieties has be preferred.

4. Management practices to be considered at different
crop stages are :
1) Before planting the seed
2) During crop establishment
3) During flowering & seed development
4) During seed maturation
5) During harvesting, threshing & processing
6) During storage

5. a) Selection of site:
 Factors critical for successful seed production are
climatic conditions, previous crop history, weed
population, disease history, isolation, position of field
in relation to other key areas, the nature of the soil,
water & other physical features of that site.
 The disease pressure is often regionally based.
 Risk of disease infection varies widely by crop,
disease & location.
 In India, incidence of Karnal bunt of wheat is
promising in Northern states.

6.  Destruction of crop residues is done based on the
type of crop, type of pathogen & size of the crop.
 Burying the residues – S. oryzae, X. campestris pv.
malvacearum.
 Burning of the debris – sclerotia which is the
primary source of inoculum in perennial grasses in
seed production fields.
 Sanitation of pruning implements, inter cultivators,
etc. which may carry viral infections. Eg: TMV

8.  In addition to detrimental effect on yield some
weeds also serve as reservoir of many seed borne
pathogens.
 Rice tungro virus, paddy blast, certain rusts cannot
complete their life cycle without alternate host-
where sexual recombination occurs.
 Perennial weeds around the fields act as over-
wintering hosts for harmful viruses
 Insects like aphids, leaf hoppers, trips & beetles
not only feed on plants but also spread many viral
diseases.

9.  Soil type, texture, aeration, acidity or alkalinity,
suppressive-ness, soil temperature are certain
factors responsible for seed & soil borne diseases.
 Covered smut of wheat is more severe in low soil
temperature & high soil moisture.
 Soil temperatures <29.5C inhibits soybean growth,
promotes seed rot & damping off, particularly if
soils are wet.

10.  Fluorescent Pseudomonas were isolated from
tobacco roots grown in suppressive soils to black
root rot (Thielaviopsis basicola), it was detected to
a depth of 1m; below 1m there was no Fluorescent
Pseudomonas & was found conducive to disease.
A highly suppressive strain CHAo was identified
as Pseudomonas fluorescens. Black root rot of
tobacco was suppressed in 36 of 39 conducive soil
samples by adding strain CHAo at 10 c. f. u/cm of
soil.

11.  It can reduce weeds, number of fungal propagules,
insects & nematodes in the soil.
 Flooding reduces Hill bunt (T. laevis) incidence in
wheat.
 Flooding causes destruction of crop debris & it
also carries the propagules of some pathogens
growing in the flood water.

12.  Excess use of N increases the incidence of rice blast,
bacterial blight in rice, Kernal bunt in wheat &
rhizoctonia seedling blight of pea, beans & vegetables.
 Late application of N in wheat increases leaf blotch.
 Deficiency of N or P results in take-all disease in
wheat.
 Excess Ca in soil- reduces bean root rot but favours
head smut of sorghum.
 Ferric chloride- reduces rice brown spot
 Sillica- reduces rice blast.
 Molybdenum- reduces Ascochyta blight on beans &
peas.

13.  Nutrients released from decomposing residues
stimulate the activity of some pathogens but they
don’t have host to attack & they die.
 Soil incorporation of green manure as cover crops
can be used effectively to reduce root rot
pathogens.
 Alfalfa is effective in suppressing disease
organisms in soil.

14.  Successive planting of different crops in the same
area, sometimes with fallow or resting period
between crops.
 It helps to reduce the buildup of root-rotting
organisms.
 Pepper may not be followed with Solanaceae crops
as these crops share many soil-borne diseases.
 Crop sequencing of cotton, sunflower and maize
increase the infection of Macrophomina
phaseolina.
 Once in 4 year rotation in lentil helps to reduce
Ascochyta blight incidence.

15.  It is the best & cheapest method of disease control.
 The term resistance describes the plant host’s
ability to suppress or retard the activity & progress
of a pathogenic agent which results in absence or
reduced of symptoms.
 Tolerant plants can endure severe disease without
suffering significant loss in yield.
 Horizontal resistance will be more useful in
subsistence agriculture.

16.  Resistant to black rot in crucifers was first identified in
Japanese cabbage cultivar Early Fuji, from which many
resistant crucifer hybrids were developed.
 Black seeded varieties in gram are more resistant to
Ascochyta blight than white seeded varieties- presence
of phenolic substances inhibitary to the pathogen.
 Coloured testa in ripened bean seeds inhibit
C. lindemuthianum.
 Anti-microbial substances in seed coat of bean, pea &
sweet pea inhibit seed infection by
C. flacumfacience pv. flacumfacience.

17. a) Clean planting material /Disease free seeds &
transplants:
 Use of healthy seeds can help growers to avoid
many costly & environment damaging fungicides
in later season.

18.  ABSTRACT
On farm research using manual seed cleaning and seed treating
by a 15% brine solution are the simple and easy practice
that did not harm to the environment. Experiments were
conducted in the two continuous seasons, 2001 wet season and
dry 2002 dry season. Ten farmers were selected to
participate the experiment. Results showed that farmer’s
fields used clean seeds decreased transmission of rice seed-
borne diseases such as brown spot, red stripe, leaf scald,
bacterial leaf blight, sheath rot and grain discoloration. Yield
increased from 12 to 15 % and quality of seeds were observed
in which 7.4-10.65% clean seeds in the dry season and 9.27-
9.6% in the wet season. Moreover, use of clean seeds
also decreased 5.83-8.73% unfilled grains in the dry season
and 8.32-8.65% discolored seeds in the wet season.

19.  Results showed that farmer’s fields used clean
seeds decreased transmission of rice seed-borne
diseases such as brown spot, red stripe, leaf scald,
bacterial leaf blight, sheath rot and grain
discoloration.
 Yield increased from 12 to 15 % and quality of
seeds were observed in which 7.4-10.65% in the
dry season and 9.27-9.6% in the wet season.
 Moreover, use of clean seeds also decreased 5.83-
8.73% unfilled grains in the dry season and 8.32-
8.65% discolored seeds in the wet season.

20.  Change in time of sowing may exploit weather
conditions that are unfavourable to the pathogen &
reduce yield losses.
 Early sowing – reduces the ergot disease in bajra
& avoids black rot disease in crucifers.
 Deep sowing favours covered smut, flag smut &
Kernal bunt in wheat, & loose smut in sorghum.
 Narrow spacing & dense seedling reduces aeration
& provide humid canopy that encourages the
introduction & spread of disease.

21.  It has indirect effect on spread of disease.
 Some forms of inoculum spread extensively during
tillage.
 Tillage buries pathogens present on the top soil
deeper where they are less likely to cause the
disease.
 Also helps in release of nutrients in soil & benefits
the crop.

22.  Practice of growing more than one crop in
alternate rows.
 Reduces disease by increasing the distance &
creating physical barrier between the plants of
same species.
 Successful intercropping partly depends upon
combination of crop plants chosen.

23.  Organic amendments increases the activity of
competing or predatory microorganisms in the soil.
 They also help in rectifying the problems related to
soil pH & make nutrients available to plant.

26.  Overhead watering can prolong the leaf wetness-
increases likelihood of germination & infection by
fungal spores.
 Excess irrigation – favours Karnal bunt
 Frequent irrigation- reduces flag smut of wheat
 Alternate wetting & drying destroys sclerotia.
 Drip irrigation delivers water directly to root zone
& at rate insufficient to disperse pathogen.

27.  Trap crop are susceptible plants grown on land
containing pathogens, they become infected &
destroys before pathogen completes its life cycle-
reducing the amount of inoculum in the area.
 Decoy crops stimulate germination of pathogen
propagules, but the pathogens are unable to
establish & infect the decoy host & die- reduces
the inoculum.

28.  Removal & destruction of diseased plants as soon
as disease symptoms are observed.
 In sorghum & pearl millet ergot ear heads are
rogued & burnt.
 In viral diseases effective roguing reduces the
spread of the pathogen.
 Loose smut spore have already been spread &
infection of the seed crop has taken place by the
time symptoms are visible- certification schemes
do not allow removal of smut-infected plants.

29.  The distance between the seed production &
commercial plots is maintained to reduce disease
incidence in seed crop.
 This distance varies from region to region based
on weather conditions.
 For loose smut of wheat & barley isolation
followed in different countries is:
Germany, UK - 50m
Holland - 100m
India - 150m

30. a) chemical protection in the field:
 Several seed borne fungi, such as Colletotricum sp.
, Cercospora kikuchii, Alternaria, Tilletia sp. etc.
and viruses such as lettuce mosaic virus, bean
common mosaic virus, cucumber mosaic virus etc.
become established in seed during flowering, seed
setting and maturation.
 Prophylactic measures using timely application of
appropriate fungicides/chemicals/insecticides or
bio agents, from early blossom to maturity of the
crop at an appropriate stage of the plant growth is
one of the effective management practice.

31.  Fungal infection of seed is often more pronounced
during the later stages of maturation, especially in
areas where seed maturation coincides with the
season of high atmospheric humidity.
 The rainfall from maturity to the harvest of the
crop appears to effect the incidence, prevalence
and severity of seed borne fungal pathogens.
 If excessive rainfall occurs during harvest, the
colonization and infection of the pods and seeds by
pathogens and saprophytic fungi cause seed
discolouration.

32.  Harvesting equipments are adjusted for minimum
kernel or seed damage and maximum cleaning.
 Timely harvesting and processing avoids the
anthracnose infection which usually occurs on
mature fruits.
 After proper processing, subsequently stored under
low temperature and low moisture content to avoid
contamination in storage.

33.  Most storage fungi belong to the genera
Aspergillus, Pencillium, Rhizopus, & Chetomium.
 Storage fungi are frequent where seed moisture
level is above safer level (>10%).
 A. niger attacks seed at moisture content of 12% at
RH 75%.

34. Physical methods:
 Seed dip in water: soaking seed in plain water at
20°c for 41 hrs- loose smut of wheat.

35. Hot water treatment:
 The seeds are dipped for specific period of time in
hot water to a particular temperature safe to the
seed embryo and deleterious to the associated
pathogen
 Useful for low volume high value seed
 Effective for internally associated fungi and
bacterial pathogens.
 High temperature damage the embryo
 Temperature and duration of treatment differs from
crop to crop

36. HOT WATER THERMAL TREATMENT FOR
CONTROLLING SEED-BORNE MYCOFLORA OF
MAIZE

37. The seed material is exposed to hot air stream for a
specific period, which is safe for viability of seed.
More effective for the pathogens associated on to
the seed surface.
Eg: Tomato mosaic virus of tomato -3 days at 70 °c

38. Safe and convenient method than hot water
treatment.
J. C. Luthra suggested this method for control of
loose smut of wheat.
Wheat seed is presoaked in water for 4-5 hrs in the
shade or in a room and then dried on ground
/concrete floor in a thin layer in sun for 1 hr
usually at noon time to eradicate the pathogen
established inside the embryo.

39. It is the reduction of inoculum density or disease
producing activities of a pathogen or parasite in its
active form or dormant state by one or more
organisms accomplished by naturally or through
the manipulation of the environment of host /
antagonist or by mass introduction of 1 or more
antagonists.
It aims at eradication and control of the pathogen
through antagonistic activity of micro organisms
which is achieved by parasitism, predation and
commensalism etc.

42. An experiment was carried out at the Oil seed Research Unit,
Marathwada Krishi Vidyapeeth Parbhani, Maharashtra, India
to evaluate the efficacy of different chemicals and bioagents
against seed/soil borne diseases of safflower on disease incidence
(PI or DI). Significantly low disease severity (DS) and low
disease incidence (DI) were recorded in treatment withT7, that
is, Trichoderma harzianum Th4d sc at 2ml/kg to the tune of
41.66% in Fusarium sp, 08.33% in Rhizoctonia sp, 06.66%
in Phytophthora sp, 04.33% in Alternaria leaf spot and
03.33% in Cercospora leaf spot respectively, in comparison
with the untreated control. The seed yield data indicated
that T. harzianum produced highest seed yield (2778 kg/ha)
followed by Captan at 0.2% (2115 kg/ha) and
Carbendazim+Mancozeb (SAFF) at 0.2% (2114 kg/ha). High
infestation of safflower seeds by causal agents of seed/soil
borne foot and root rots, reduction of seed germination and
considerable infection transmission from seed to seedling
were determined. Fungicide seed treatments, T1 to T8, markedly
decreased incidence of diseases. Though the treatment with T7,
that is, T. harzianum recorded the disease incidence, it produced
the highest yield

44. Harmless to human beings and animals
Cheaper than pesticides (50%).
High Cost Benefit ratio
Highly effective throughout the crop
growth period with high rhizosphere
competency.
Easy to deliver.
Improve plant growth.
Increases yield

45. Abstract
Seeds contaminated with pathogens are the primary inoculum for plant
diseases in many food crops. Conventional treatments for seedborne diseases
use hot water, chlorine or fungicide applications. A novel seed treatment
method based on non-thermal plasma generated by an air dielectric barrier
discharge (DBD) device was evaluated in this study as an alternative to these
conventional treatments. The non-thermal plasma at atmospheric pressure and
room temperature consisted of partially-ionized gases that are chemically
reactive. The antimicrobial activity of non-thermal plasma was evaluated
against an important seedborne pathogen, Gibberella fujikuroi,that causes
bakanae disease in rice. Non-thermal plasma treatments effectively inhibited
the growth of G. fujikuroion nutrient growth medium and reduced the number
of fungal colony forming units (CFU) on the rice seed surface by > 92% after
120 s exposure. Effective exposure times to 50% (ET50) and 90% (ET90)
control of G. fujikuroiCFU on the seed surface were 9 and 76 s, respectively.
Ten minutes of non-thermal plasma treatment on seeds infested with G.
fujikuroisignificantly reduced disease development. No adverse effects were
detected on the seedling emergence and height when non-infested seeds were
treated with nonthermal plasma for up to 20 min. The treated seeds
germinated and grew similarly compared with non-treated non-infested seeds.
This study indicates that non-thermal plasma had antifungal activity and
showed potential as an effective disinfection technique to reduce the
contamination of seedborne fungal pathogens from seed surfaces without
compromising seed health

47. Abstract Thirty six rice seed samples of varieties BR6, Pajam
and Joya were collected from Parshuram upazila, Feni district of
Bangladesh and nine seed-borne fungi were detected from these
seed samples. The identified fungi were Fusarium oxysporum,
F. moniliforme, Bipolaris oryzae, Alternaria padwickii,
Curvularia lunata, Aspergillus flavus, Aspergillus niger,
Penicillium sp. and Nigrospora oryzae. Five different plants
extracts viz. garlic, allamanda, neem, chirata and bishkatali with
two dilutions (1:1 & 1:2) were tested for seed treatment. Garlic
extract (1:1) dilution found best for three varieties which
successfully reduced seed-borne infection and also increased
seed germination up to 68.39% over control. Neem (1:1) and
chirata (1:1) extracts also increased seed germination up to
66.09% and 67.81%, respectively. Based on the present study, it
may be concluded that among the five plant extracts with two
dilutions (1:1 & 1:2), garlic (1:1) is most effective in controlling
seed-borne fungal flora of rice followed by neem (1:1) and
chirata (1:1) extract.

54. Application of chemical to seed is cheapest method &
most effective method for controlling seed borne
pathogens.
Fungicidal seed treatment may kill or inhibit seed born
pathogens by forming protective covering.
FORMULATIONS:
Seed treatment chemicals are available in different
formulations.
 Dusts
Slurry
Liquid
Fungicidal-insecticidal formulation

55.  Simple and economical
 Add the required quantity of fungicide and shake
them in a closed vessel or a rotary drum for 5-
15minutes.

57.  1. Seed Dip Method:
Involves dipping of the seed in fungicide solution.
Recommended for seeds with tough seed coats.
The seed should be treated just prior to planting
This method is mainly used for treating vegetatively
propagated materials like tubers, bulbs and cuttings

58.  Water dispensable fungicide formulations are
mixed in water to form slurry.
 Seeds are sprayed with high conc. Fungicide
solution and dried.
 The chemical is deposited on the surface of seed in
the form of thin paste.

61.  ABSTRACT
 In organic seed production more than a half of seed lots
are often discarded due to heavy infection with seed
bornepathogens. To prevent this, various techniques are
used:
 seed heat treatment, ultrasound treatment, brush
cleaningand seed dressing with plant extracts or natural
chemicals. In 2008, the efficiency of wheat seed
treatment with the stone meal was tested and the results
of preliminary investigation are presented. Two tests
were performed using the official procedure for seed
health testing.


62. Test 1:
Heavily infected wheat seedwas treated with the stone
meal EKORAST (particle size <0.08 mm). Dry and
wet treatment procedures were applied: both with 1, 2,
10 and 20%. Heavy application (10 and 20 kg per 100
kg of seed) significantly increased germination and
energy of wheat seed, and it was effective against
bacterial pathogensand some fungi, but only partially
effective against heavy infection of Fusariumspp.
However, the amounts of stone meal (10 and 20%) are
practically not applicable, and adhesion of stone meal
to the seed should be improved.

64. Test 2:
Wheat cleaned seed of seven genotypes was wet
treated with Ekorast (1 %) and chemical fungicide
Vitavax 200FF (250 ml/100 kg). The untreated seed
was used as control. There were no significant
differences between the three variants in germination
and energy. The stone meal Eko-rast was equal or
better than Vitavax 200FF in seed protection against
seed borne pathogens, and could be recommended
for seed treatment in organic seed production. Search
for an additive with better adhesion to seed is under
way.

69. Mineral Percentage
SiO2 56.9%
CaO 8.8%
MgO 5.9%
K2O 3.0%
P2O5 0.8%
Fe2O3 1.3%
Al2O3 8.7%
Na 0.8%
Mn 54.2mg/kg
Zn 21.2mg/kg
Cu 35.3mg/kg
Pb 2.2mg/kg
Cd 0.3mg/kg

75.  Protects germinating seeds and seedlings from soil
and seed borne pathogens / insects
 Seed germination enhancement
 Uniform crop stand, even in adverse conditions
(less/high moisture)
Treated Untreated

76.  It was potato seed certification, began in Germany
(1990s) & soon after in US, with the aim of
stooping the spread of viruses responsible for leaf
roll & other viral disease.
 Certification goes hand in hand with seed quality
control in which the most important seed qualities
are viability, purity & health.

77.  Certification involves strict procedure for labeling
& sealing seed packs.
 Certification is limited generation system based on
4 seed classes.
 Certification shall be completed in 6 phases.
 Compulsory requirements to be followed for
certified seed production: application, field
eligibility, isolation, field inspection, offtypes,
weeds, diseases.

78.  Quarantine is a legislative (regulatory) attempt to
exclude pathogens from invading into the areas
where they do not exist by monitoring the import
and export of plant, seed or planting material to
prevent spread of diseases and pests.
 It aims to prevent the entry of dangerous
pathogens but not the movement of biological
material.

79. Agrawal, V. K. and Sinclair , J. B. (1987) Principles of seed
pathology, CRC press, BOCA Raton, Florida.
Vishunavat, K. (2009) Fundamentals of seed pathology, Kalyani
publishers, New Delhi.
Anam, M. K., Fakir, G. A., Khalequzzaman, K. M., Hoque, M. M.,
Abdur Rahim. (2002) Effect of seed treatment on incedence of
seed-borne diseases of okra. Pakistan Journal of Plant
Pathology. 1(1): 1-3.
Lindsey du Toit, WSU Mount Vernon. Infection of Seed &
Transmission of Seed Borne Pathogens. NWREC
Pham Van Du, Huynh Van Nghiep and Nguyen Duc Cuong. (2003)
Application of seed cleaning in management of seed-borne
diseases of rice. OMONRICE: 11. pp 103-109.
Rahman, M. M. E., Ali, M. E., Ali,M. S.,. Rahman,M. M., and Islam,
M. N. (2008) Hot water thermal treatment for controlling
seed-borne mycoflora of maize. Bangladesh Agricultural
Research Institute, International Journal Sustainable Crop
Production. 3(5): 5-9.