This document discusses seed borne diseases and their management. It notes that seed borne pathogens can cause significant losses through reduced germination, seedling mortality, and yield losses. Some key seed borne diseases mentioned include late blight of potato, brown spot of rice, and downy mildew of pearl millet. The document then outlines methods for detecting seed borne pathogens, including visual examination, growing tests, and molecular methods. It discusses management approaches like seed selection, quarantine, hot water treatment, chemical seed treatments, and biological seed treatments using microbes like Trichoderma and Pseudomonas.

2. SEED
BORNE DISEASES AND MANAGEMENT
Prepared by:
MANJU. K. P
RAD/13-18

3. INTRODUCTION

4.  Seed borne diseases assumed a greater importance to seed
industries.
 Seed borne pathogens results in seed rots, seedling decay,
pre and post emergence mortalities, abnormalities,
discoloration, reduced seed size and shrivelledness of
seeds.
 The seed borne pathogens not only affect the market value
but also nutritive value of the products.

5. Losses due to seed borne diseases
 Late blight of potato caused by Phytopthora infestence was responsible for Irish famine during
1845.
 Brown spot of rice caused by the seed borne Helmenthosporium oryzae was responsible for
Bengal Famine during 1942.
 The loss by downey mildew of pearl millet in Rajasthan in 1962-64 was estimated to be 20
million rupees.
 Occurrence of tobacco bud blight in soybean caused 66.43% yield loss. (Dhingra and Chenulu,
1980)
 AICRP on millet showed an average annual loss of about 30% in high yielding varieties
equivalent to 270 million $ annually.
 Cause economic losses in cultivated crops world wide.

6. Losses due to seed borne diseases
Crop Diseas/ Pathogen Yield loss (%)
Rice Blast 75
Bacterial Blight 6-60
Brown spot 50-90
Sheath Rot 50
Wheat Loose smut 100
Ear cockle 100
Chickpea Ascochyta rabici 80-90
cowpea Anthracnose 30-35
Leaf crinkle virus 3-61
Soya bean Tobacco bud blight 66
Soya bean mosaic virus 25-94
Cucumber Cucumber mosaic virus (planting of 0.5% infected seeds) 34-53
Cabbage Black rot, Planting 2 seeds infected by Xanthomonas campestris out of 10,000
seeds.
Black rot epidemic occurs

7. Crop Disease Causal organism
Brinjal Fruit rot Phomopsis vexans
Carrot Black root rot or
Seedling blight
Alternia radicina
A.dauci
Onion Damping off
Downy mildew
Purple blotch
Stemphylium Blight
Botrytis allii
Peronospora destructor
Alternia porri
Stemphylium vesicarium
Pepper and chilli Anthracnose or fruit rot Colletrotrichum capsici
Radish Grey leaf spot
Leaf spot
Alternia brassicae
A. Raphani
Crucifers Grey and black leaf
Spot
Alternia brassicae
A. Brassicicola
Tomato Buck eye rot
Damping off
Early Blight
Late blight or Fruit rot
Phytophthora parasitica
Phythium aphanidermatum
Alternia solani
Phytopthora infestans
Important seed borne diseases

8. Crops Diseases Causal organism
Wheat Loost smut
Karnal smut
Flag smut
Ustilago segetum var. tritci
Neovossia indica
Urocystis agropyri
Rice Bunt
False Smut
Stack burn
Neovossia horrid
Ustilaginoidea virens
Pyricularia oryzae
Trichoconiella padwickii
Maize Black kernel rot
Cob rot
Southern leaf blight
Botryodiplodia theobromae
Fusarium Moniliformae
Drechlera maydis
Pearl millet Downy mildew
Smut
Sclerospora graminicola
Tolyposporium penicillsriae
Sorghum Anthracnose
Kernel or grain smut
Downy mildew
Colletotrichum graminicola
Sphacelotheca sorghi
Peronosclerospora sorghi

9. Cotton Anthracnose
Wilt
Alternaria blight
Colletotrichum indicum
F.oxysporum f.sp.vasinfectum
Alternaria macrospora
Sugarcane Red rot
Wilt
Pineapple Disease
SMUT
Mosaic(s)
Colletotrichum falcatum
Fusarium moniliforme
Ceratocystis paradoxa
Ustilago Scitaminea
Virus
Groundnut Charcoal rot
Crown rot
Yellow mould/Aflatoxin
Macrophomina phaseolina
Aspergillus niger
Aspergillus flavus
Sunflower Alternaria blight
Downy mildew
Charcoal rot
Alternaria helianthi
Plasmopara halstedii
Macrophomina phaseolina
Soybean Anthracnose
Pod & stem blight
Purple seed stain
Colletotrichum dematium
Phomopsis sojae
Cercospora kikuchii
Chickpea Ascochyta blight
Wilt
Gray mold
Alternaria blight
Ascochyta rabiei
Fusarium oxysporum f.sp. Ciceri
Botryris cinerea
Alternaria circinum

10. Viral diseases
Virus name Crop
Tobacco mosaic virus Tomato
Alfa-alfa mosaic virus Alfa-alfa
Crinkle virus Black gram
Cucumber mosaic virus Cucumber
Sugarcane grassy stunt virus sugarcane
Citrus ring spot virus Citrus
Banana bunchy top virus Banana
Cowpea mosaic virus cowpea

11. As a seed grower, what do I need to worry about?
 RED ALERT diseases:
 highly virulent, highly seed-borne
 ORANGE ALERT diseases:
 moderately virulent and highly seed-borne
 OR highly virulent and moderately seed-borne
 YELLOW ALERT diseases:
 Moderately virulent and seed-borne

12. RED ALERT DISEASES
 Brassica Black Rot Bacteria (Xanthomonas
campestris)
 Brassica Blackleg Fungus (Phoma lingam /
Leptosphaeria maculans )
 Lettuce Mosaic Virus
 Carrot Bacterial Blight (Xanthomonas
campestris pv. carotae)
 Tomato Mosaic Virus

13. Orange alert diseases
Carrot Fungal Blights
 Alternaria blight (Alternaria dauci)
 Cercospora blight (cercospora carotae)
Tomato bacterial diseases
 Bacterial canker (Corynebacterium michiganense pv,
michiganense)
 Bacterial Spot (Xanthomonas campesiris pv, vesicatoria)
 Bacterial Speck (Pseudomonas syringae )
Onion white rot fungus (Sclerotinia sclerotiorum)

14. The seed borne pathogens may result in
(i) Loss in germination
(ii) Discoloration and shriveling
(iii)Development of plant diseases
(iv)Distribution of pathogen to new areas
(v) Introduction of new strains or
physiologic races of the pathogen
along with new germplasm from other
countries
(vi)Toxin production in infected seed etc.

15. Methods for Detecting Seed Borne pathogens
* Visual examination
* Water Agar method
* Standard blotter method
* Examination of seed soaked in water
* Examination of seed washing.
* Embryo count method
* Rolled paper towel method
* Examination of dry seeds
* Growing on test
* Phage plaque method
* PCR
* ELISA
* Electron microscopy

16. Visual inspection of seeds
 Presence of smut balls of
smut of sorghum and pearl
millet,
 sclerotia (ergot) of sorghum,
pearl millet and triticale,
 sclerotia of black scurf
diseases of potato embedded
on tuber skin can be easily
be detected by visual
examination.
 Black powder of bunt spores
can be seen in wheat and rice.

17. Paths of seed infections

18. The infestation/contamination of the seed may occur during
harvesting, threshing and processing. The pathogen may, thus, be
carried with the seeds in three ways.

22. MANAGEMENT OF SEED BORNE DISEASES:
AN INTEGRAL APPROACH
A) Seed selection
B) Quarantine
C) Seed treatments
E) Cultural practices.
F) Cultivation of resistant varieties

23. Approved sources for quality seeds

24. Plant Quarantine: All activities designed to
prevent the spread of quarantine diseases
and pests to ensure their official control
"Plant Quarantine is legal enforcement of
measures planned to prevent pests and
diseases from spreading to new areas, or to
prevent them from multiplying and
spreading further incase if they have
already found entry"
(www.plantquarantineindia.org)

25. Notification to regulate the
transport of plant / plant
material within the country.
Domestic Quarantine

26. Sl. No. Pest Prohibited from
1 Banana bunchy top Assam, Kerala, Orissa, Tamil Nadu,
West Bengal
2 Mosaic disease of banana Gujarat and Maharashtra
3 Potato wart (Synchytrium endobioticum) West Bengal
4 Apple scab (Venturia inequalis) Jammu and Kashmir
Domestic quarantine regulations were in vogue for the
following pests

27. SEED TREATMENTS FOR DISEASE MANAGEMENT
• Physical seed treatments
• Chemical treatments
• Biological seed treatments

28. HOT WATER TREATMENT
 Advantages:
 Most effective
 Kills disease on both inside and outside of seed
 Can fully eradicate heat-sensitive pathogens
 no residue
 Disadvantages: –
 requires an investment –
 Requires careful handling,
 can damage seed –
 Can’t be done as easily during harvest, so often requires wetting and re-
drying seed

29. Hot Water Requirements
 42-50°C (118-122°F)
 15-25 minutes
 Seed fully immersed,
 typically in cotton bags
 Need a setup with temperature control
 Better option is a lab-grade water bath
incubator
 Does not damage seed if done carefully

30.  Temperature should be sufficiently high to kill the associated
pest/pathogen but not the host. However, in most cases, margin of
safety is very narrow and, therefore, the temperature should be
very accurately controlled. Some recommended hot water
treatments (Kahn, 1977) are:
• Against nematodes: chrysanthemum- 48° C for 25 min; potato
tubers- 45° C for 5 min
• Against insects and mites: strawberry runners- 46° C for 10 min;
• Against viruses: Grape vine, 45° C for 120-180 min; sugarcane sets-
50° C for 120 min; potato tubers- 50° C for 17 min;
• Against fungi: Celery seed, 50° C for 25 min; wheat seed, 52-54° C
for 10 min;

31. Brassica
 Hot water treatment at 52ºC for 30 minutes against
 Alternaria brassicae, A. brassicicola, Phoma lingam, Xanthomonas
campestrispv. Campestris.
Rice
 Hot water treatment at 52ºC for 30 minutes against Nematode-
(Aphelenchoides besseyi) & Bacteria-(Xanthomonas campestrispv.
oryzae)
 Bacterial blight of cluster bean (X. campestris pv. cyamopsidis) at
56° C for 10 min (Srivastava and Rao, 1963);
 Bacterial blight of sesame (X. campestris pv. sesami) at 52° C for
10 min (Rao and Durgapal, 1966).

32. Chemical seed treatment

33. Important chemicals used for seed treatment
Technical Names Available formlation
Captan 50% WP
Carbendazim 50% WP
Deltamethrin 2.8 % EC
Imidacloprid 70% Ws, 48% Fs
Metalaxyl 35% Ws
Thiamethoxam 70% Ws, 30% Fs
Thiram 75% Ws

34. Biological seed treatment

35. IDEAL CHARACTERISTICS OF BIOCONTROL AGENTS
 Not be pathogenic - plant, human, animal and other beneficial microorganisms
 Should be broad spectrum
 Fast growth and sporulation
 Withstand adverse environment condition
 Can be cultured under artificial media

36. Pseudomonas fluorescensTrichoderma viride
Bacillus subtilis

37. RECOMMENDATION OF BIOCONTROL AGENTS AS SEED
TREATMENT IN DIFFERENT CROPS
Name of crop Pests/diseases Seed treatment
Rice Root rot disease, other insects/pests,
bacterial sheath blight
Trichoderma 5-10 g/kg. seed (before
transplanting)
Pseudomonas flourescens 0.5% W.P. 10 g/kg.
Wheat Termite, bunt/false smut/loose
smut/covered smut
Teat the seed before sowing.
T. viride 1.15 % WP @ 4 g/kg.
Gram Wilt, damping off Seed treatment with Trichoderma viride 1% WP
@ 9 g/kg seeds
Sunflower Seed rot, jassids, whitefly Trichoderma viride @ 6 g/kg seed.
Pigeon pea Wilt, blight and root rot Trichoderma spp. @ 4 g/kg. Seed
Pea Root rot, White rot Seed treatment with
Bacillus subtilis or Pseudomonas fluorescens
Sugarcane Root rot, wilt Trichoderma sp. 4-6 g/kg.

38. Coriander Wilt Trichoderma viride @ 4 g/kg seed.
Brinjal Bacterial wilt Pseudomonas fluorescens @ 10g/kg.
Leguminous Vegetables Soil borne infection, Nematode Trichoderma viride @ 2 g/100g seed.
Cruciferous vegetables
(cabbage, cauliflower,
broccoli, knol-khol, radish)
Soil / seed borne diseases
(Damping off) Root knot nematode
Seed treatment with Trichoderma viride
@ 2 g / 100 g seeds
Pseudomonas fluorescens and Verticillium
clamydosporium @ 10g/kg seed as seed dresser
Capsicum Root knot nematode Pseudomonas fluorescens 1% WP, Paecilomyces
lilacirius and Verticillium chlamydosporium 1%
WP @ 10g/kg as seed dresser.
Chillies Anthracnose spp. damping off Seed treatment with Trichoderma viride 4g/kg
Bhendi Root knot nematode Paecilomyces lilacinus and
Pseudomonas fluorescens @ 10 g/kg as seed
dresser.
Tomato Soil borne infection of fungal
diseases, early blight, damping off,
wilt
T. viride @ 2 g/100g seed.
Pseudomonas fluorescens and V. clamydosporium
@ 10g/kg as seed dresser.