This document describes methods for screening rice for resistance to diseases. It focuses on screening for resistance to rice blast caused by the fungus Magnaporthe oryzae. Screening can be done in greenhouses by artificially inoculating rice seedlings or in blast nurseries with natural infection. For greenhouse screening, isolates are prepared from fungal stocks and sprayed onto seedlings, which are then evaluated for disease symptoms. Screening in blast nurseries involves planting test lines between spreader rows to ensure natural infection from diverse pathogen races under favorable conditions.

1. Screening for Resistances to RiceScreening for Resistances to Rice
DiseasesDiseases
Yongli Zhou/Jauhar Ali*/Zhikang Li
Institute of Crop Sciences/
National Key Facility for Crop Gene Resources and
Genetic Improvement, CAAS
* International Rice Research Institute

2. IntroductionIntroductionIntroductionIntroduction
Methods of screening rice resistanceMethods of screening rice resistanceMethods of screening rice resistanceMethods of screening rice resistance
to diseasesto diseasesto diseasesto diseasesto diseasesto diseasesto diseasesto diseases
◆◆◆◆ Rice blastRice blastRice blastRice blast
◆◆◆◆ Rice sheath blightRice sheath blightRice sheath blightRice sheath blight
◆◆◆◆ Rice bacterial blightRice bacterial blightRice bacterial blightRice bacterial blight
◆◆◆◆ Virus diseasesVirus diseasesVirus diseasesVirus diseases

3. Introduction of rice diseasesIntroduction of rice diseasesIntroduction of rice diseasesIntroduction of rice diseases

4. Fungus Diseases
Blast, Sheath blight, Brown spot, Downy mildew, False
smut…
Bacterial Diseases
Bacterial leaf blight, Bacterial leaf streak, Bacterial stripe…
Rice Diseases
Virus and Mycoplasma-like organism (MLO) Diseases
Dwarf, Stripe, Yellow dwarf (MLO), Black-Streaked
Dwarf, Orange leaf, Tungro and similar diseases, Yellow
mottle virus…
Disease Caused by Nematodes
White tip, Stem nematode, Root nematode, Rice cyst
nematode…

5. Screening Methods for Resistance to RiceScreening Methods for Resistance to RiceScreening Methods for Resistance to RiceScreening Methods for Resistance to Rice
DiseasesDiseasesDiseasesDiseases
Technique of Screening RiceTechnique of Screening RiceTechnique of Screening RiceTechnique of Screening Rice
Resistance to BlastResistance to Blast

6. SymptomsSymptoms of Rice Blast
Seedlings killed by leaf blast Lesions on leavesSeedlings killed by leaf blast Lesions on leaves
Neck blast Infected panicle and spikelets

7. Infection
Spread by
Air-borne conidia
Leaf blast
Panicle blast
Re-Infection Seedling blastNeck blast
Causal agent
Magnaporthe grisea (Pyricularia oryzae)
Disease cycle of rice blast
Mycelium and conidia on
diseased straw and seeds are
the principal over-wintering organs
Leaf blast

8. Effects of environmental conditions on
disease development
Low night temperature (~20 ℃℃℃℃) and high
humidity (>90%) are essential for infection and
development of lesion
℃℃℃℃
The slight shading from sunlight at the early
stage of lesion development fosters extension of
the lesion
A high nitrogen supply increases susceptibility
of rice

9. Screening Methods for rice resistance to blastScreening Methods for rice resistance to blast
1. Screening in greenhouse by artificial inoculation -
seedling blast
2. Screening at Blast Nursery – Leaf and panicle blast
3. Inoculation Method for Evaluating Panicle Blast (or
Neck Blast) Resistance

10. To rapidly screen the resistant materials and identify
Objective:
Screening in greenhouse by artificial inoculation
To rapidly screen the resistant materials and identify
the race-specific resistance of rice cultivars, the
resistance can be evaluated in greenhouse by artificial
inoculation.

11. Isolate StockIsolate Stock
Isolates for stock are revived in
prune agar slants, and incubate
at 28℃ for 10-14 days
The slant is added with water
and mycelia that grow well will be
macerated with sterile needle.
The suspension will be poured
℃
Paper disks
cotton
The suspension will be poured
onto prune agar plates.
Incubated at 28 ℃ for 7 days
Scrap with glass slice to move
the mycelia, add the sterilized
paper disks, and induce
sporulation in light for 4-10 days.
Stock in small bottles. Kept in -
20℃ for years.
Silica gel

12. Preparation of Isolates
Stock cultures in
paper disks are
revived in prune
agar slants, and
incubate at 28℃℃℃℃ for
10 days
Stocks Transplant to
slant

13. The slant is added with water and mycelia that grows well will
be macerated with sterile needle. The suspension will be
poured onto prune agar plates. Incubated at 28 ℃ for 7 days

14. Scraping, scrap with glass slice to move the mycelia, and induce
Incubate in sporulation
cabinet in dark, 28℃℃℃℃
Scraping Plate full of spores
Scraping, scrap with glass slice to move the mycelia, and induce
sporulation in light for 4 days.
About 10-20 ml sterilized water will be poured into Petri dishes
containing conidia and will be gently scraped the surface lf the
mycelia with glass slide. Conidial suspension is filtered through
nylon mesh.
The suspension’s concentration is determined using a
hemacytometer and will be adjusted until around 5×10 conidia
per ml.

15. Medium PreparationMedium Preparation
A) Prune Agar (PA)
Prunes: 3 pieces
α- Lactose: 5g
Yeast Extract: 1g
Agar: 20g
H2O: 1L
B) Water Agar (WA)
Agar: 40g
H2O: 1L
Add some Streptomycinsulfate
sterile powder beforepouring for
aqueous injection antibacterial

16. Preparation of Plant MaterialsPreparation of Plant Materials (( ----4~6 leaf )4~6 leaf )

17. Artificial inoculationArtificial inoculation
----SprayingSpraying

18. Kept in cages at 25℃,
overnight

19. Kept in a mist room, 25℃
Diseased leafDiseased leaf

20. Process Time
Isolates revival
(From stock to prune slant, incubated at 28℃)
7 -10 days
Germination, incubated in 25 ℃ 2 days
sowing, 2reps, kept in greenhouse 14 days
Plating the isolates, incubated at 28℃ 7 days
Scraping, incubated in light 3 days
Inoculation, kept in cages, 25℃ 1 day ,
overnight
Kept in mist room, 25℃ 7 days
scoring 1 day
Totally 28 days

21. For greenhouse and field :For greenhouse and field :
CODE (Predominant lesion type)
0 No lesions observed
1 Small brown specks of pinpoint size or larger brown specks without
sporulating center
3 Small, roundish to slightly elongated necrotic sporulating spots, about 1-2 mm
AssessmentAssessment
3 Small, roundish to slightly elongated necrotic sporulating spots, about 1-2 mm
in diameter with a distinct brown margin or yellow halo
5 Narrow or slightly elliptical lesions, 1-2 mm in breadth, more than 3 mm long
with a brown margin
7 Broad spindle-shaped lesion with yellow, brown, or purple margin
9 Rapidly coalescing small, whitish, grayish, or bluish lesions without distinct
margins
Note: Lesion type 5, 7, and 9 are considered typical susceptible
lesions

22. AssessmentAssessment
Lesion type
0 1 2 3 4 5
Disease Leaf Area (DLA)
MAFF Microorganism Genetic Resources Manual No.18 ISSN 1344-1159

23. Objectives :
• Encourage the use of genetically diverse sources of
resistance in the development of varieties with
durable blast resistance.
Screening at Blast Nursery (BN)
durable blast resistance.
• Evaluate the varietal reaction of selected varieties
and breeding lines against diverse populations of the
fungus P. grisea around the world.
• Monitor the type and distribution of virulence patterns
of the blast pathogen in rice growing countries.

24. Spreader rows
Breeding lines
BN screening
The nursery is composed
of check varieties, blast
monogenic lines, and
improved breeding lines
(test entries)
Local resistant and
susceptible cultivars
should be selected and
added to the test set by
the cooperator.

25. Nursery Establishment and ManagementNursery Establishment and Management
A. Testing seasonA. Testing season
Blast symptoms may develop whenever proper environmental
conditions exist. However, tests conducted during the rainy
season are easier to manage as there is an adequate waterseason are easier to manage as there is an adequate water
supply and the conditions are more favorable for disease
development. The airborne spore population is generally
highest about a month after the regular rice growing season
begins. Considering these factors, an appropriate testing
season should be selected to meet local conditions. The leaf
blast and neck blast sets may be sown in a synchronized
manner so that scoring for each can be done at about the same
time.

26. B. Test PlotB. Test Plot
Land for test plots should be of uniform fertility with
shady surroundings and wind barriers. The plot
should be built on upland soil; but if on lowland, it
may be constructed one foot above the prevailingmay be constructed one foot above the prevailing
water level during the rainy season. The convenient
plot size is about 1.2 meters wide and 15-20 meters
long. Alternate narrow alleys are useful footpaths.

27. C. FertilizersC. Fertilizers
Abundant nitrogen is necessary to ensure adequate
infection of Pyricularia grisea. A minimum of 100 to
120 kg N/ha in the form of ammonium sulfate may be
applied with half at seeding 15 days after seeding.
Also, superphosphate at the rate of 50 kg P205/haAlso, superphosphate at the rate of 50 kg P205/ha
may be applied before seeding. Since under upland
conditions rice frequently suffers from iron deficiency
or other nutritional problems, we recommend that
high levels of animal manure also be applied.

28. D.D. Planting methodPlanting method
a) Testing rows and border rows. Testing rows of 30 or 50 cm long (one
row per test entry) should be 10 cm apart. Two to three border rows
lengthwise on both sides are to be planted at each end of the plot.
Border rows serve as spreader rows by continuously supplying inoculum
of blast pathogens to test entries. A mixture of several broadlyof blast pathogens to test entries. A mixture of several broadly
susceptible local cultivars are planted in border rows to ensure presence
of inoculum consisting of diverse races of the blast pathogen including
those in farmer’s fields. Extremely susceptible cultivars are avoided as
spreaders since plants are rapidly killed.
b) Rate of seeding. Five grams of seed are required for each 50 cm row
(1 gram/10cm).

29. E.E. Care of the blast nurseryCare of the blast nursery
Since there is no replication, uniform distribution of inoculum and
disease development by proper management are crucial for a precise
evaluation. Plots are to be watered twice or more times each day if no
rain falls. One watering period should extend to at least an hour or
more, depending on prevailing weather conditions. Watering in the
afternoon (about 5 or 6 p.m.) can be particularly effective in raising theafternoon (about 5 or 6 p.m.) can be particularly effective in raising the
humidity during the night.
During the dry season when it is windy, it is difficult to obtain a good
blast development in the nursery. Blast can be induced by covering the
plots with a plastic film just before sunset and removing it the following
morning at about 7:00am to 9:00am. With plastic covering, the dew
period is prolonged, thereby enabling the conidia that lodged on the
leaves to germinate and penetrate the cells of the plant.

30. F. InoculumF. Inoculum
Past experiments have shown that ordinary, natural airborne
spores are present in sufficient quantity to start infection.
In the dry season, when the population of airborne spores is low,
inoculum may be provided by collecting diseased leaves,
chopping them into pieces, 3 to 6 cm long, and uniformly
scattering them over the plot about 10-15 days after sowing.scattering them over the plot about 10-15 days after sowing.
Infected plants can also be transplanted between border rows.
Spraying with the susceptible border rows with spore suspension
two weeks after sowing may help initiate infection.
Another method to insure sufficient inoculum is to plant
susceptible varieties on a whole plot near the test plots 2-3 weeks
before the test begins. This will serve as a bombardment plot.

31. ProtocolProtocol
Germination of the seeds
Sowing (3 reps, 5-10 grams/line/rep)
14 days later, introduce the sensitive lines
30 days later, scoring
Select the resistant lines
Transplant to the greenhouse or field
Harvest the seeds

32. Data CollectionData Collection
0 No lesions
1 Small brown specks of pinpoint size or larger brown specks without sporulating center
2 Small roundish to slightly elongated, necrotic gray spots, about 1-2 mm in diameter, with a
distinct brown margin. Lesions are mostly found on the lower leaves
3 Lesion type is the same as in scale 2, but a significant number of lesions are on the upper
SCALE (for blast nursery, Leaf Blast )
The scales to be used in scoring are those from the 3rd edition of the "Standard Evaluation
System for Rice" (1988), where a scale of 0-9 is adopted for classification of blast reactions
as follows:
3 Lesion type is the same as in scale 2, but a significant number of lesions are on the upper
leaves
4 Typical susceptible blast lesions, 3 mm or longer, infecting less than 2% of the leaf area
5 Typical blast lesions infecting 2-10% of the leaf area
6 Typical blast lesions infecting 11-25% of the leaf area
7 Typical blast lesions infecting 26-50% of the leaf area
8 Typical blast lesions infecting 51-75% of the leaf area and many leaves dead
9 More than 75% leaf area affected
NOTE: Use this scale only for the nursery. Actual estimation of blast affected leaf area (%) is recommended
for field assessment of blast disease together with predominant lesion type (see coding system for lesion type).

33. Inoculation Method for Evaluation of Panicle Blast (orInoculation Method for Evaluation of Panicle Blast (or
Neck BlastNeck Blast) Resistance) Resistance
The evaluation of large number of test entries for panicle
(neck) blast resistance under field conditions is difficult
due to different maturity of test entries.due to different maturity of test entries.
Accordingly, the resistance of any entries showing low
panicle infection under field conditions should be
confirmed using artificial inoculation.

34. The method involves injection of aqueous spore suspension (2
x 105 spores/ml) with a syringe (Hamilton syringe, 1 ml
capacity with removable and replaceable metal needles, point
style 22°).
ProtocolProtocol
Inoculation is done soon after panicle emergence when the
distance between the collar of the flag leaf and panicle base
(neck node) is approximately 3 cm. Spore suspension (0.05
ml/panicle) is injected into the uppermost internode 2 cm
below the panicle base. At least five panicles per test entry
should be inoculated including both the primary and
secondary tillers.

35. Injection Cotton surrounding

36. Typical blast lesions appear 7 days after inoculation. While
lesions extend up to the neck in susceptible cultivars, lesions
are necrotic and are restricted to the point of infection in
resistant cultivars. This test showed clear-cut reaction.
There were, however, differences in the sizes of the lesions.
Due to variation in spikelet sterility in different susceptible
cultivars, characterization of the lesion in the neck region iscultivars, characterization of the lesion in the neck region is
preferred as a sole criterion.
This method does not require plants to be inoculated in a
humid chamber. All test entries with different heading dates
can be inoculated at different times or planting can be adjusted
to synchronize heading.

37. The results from this method showed that panicle
blast reactions of some cultivars inoculated with 2
isolates of P. grisea were different from their leaf
blast reactions.
IB-1 IB-9
Cultivar Leaf
blast
Panicle
blast
Leaf
blast
Panicle
blastblast blast blast blast
Tres Marias R R R R
Dawn S S R R
IAC-47 S S S R
Araguaia R S R R
Carreon R S R R

38. The neck blast (panicle blast) nursery should be screened
under conditions that favor the disease development. The
entries should be planted in hills in a two-meter row plot.
Two replications should be included. The entries should be
in rectangular blocks surrounded by a row of the local
susceptible check sown perpendicular to the test rows and
two rows for both sides. Resistant local variety can also be
included and should be planted side by side to the susceptibleincluded and should be planted side by side to the susceptible
local varieties with different maturity.
For each plot, record the number of panicles examined, and
the number of panicles with severe neck node (panicle)
infection or lesion covering completely around node, neck or
the lower part of panicle axis (symptom type 7-9, see scale
below). At least 100 panicles per entry should be scored.

39. Scoring Scale (based on symptoms)Scoring Scale (based on symptoms)
0 No visible lesion or lesions on only a few pedicels
1 Lesions on several pedicels or secondary branches
3 Lesions on a few primary branches or the middle part of panicle axis
5 Lesion partially around the panicle base (node) or the uppermost internode5 Lesion partially around the panicle base (node) or the uppermost internode
or the lower part of panicle axis near the base
7 Lesion completely around panicle base or uppermost internode or panicle
axis near the base with more than 30% of filled grain
9 Lesion completely around panicle base or uppermost internode or the
panicle axis near the base with less than 30% of filled grains.

40. For the mass evaluation of neck blast (panicle blast) incidence may be
computed as follows:
Scoring Scale (based on symptoms)Scoring Scale (based on symptoms)
Severe neck blast = No.of panicles with severe infection (Symptom type 7-9 only)× 100
Incidence (%) Total number of panicles observed
Scoring for severe neck blast (panicle blast) incidence may be done as
follows:
0 No incidence
1 Less than 5%
3 5 - 10%
5 11 - 25%
7 26 - 50%
9 More than 50%

41. Scoring Scale (based on symptoms)Scoring Scale (based on symptoms)
00 11 33

42. Scoring Scale (based on symptoms)Scoring Scale (based on symptoms)
77 9955

43. Technique of Screening Rice ResistanceTechnique of Screening Rice Resistance
to Sheath Blightto Sheath Blight
Methods of Screening Rice Resistance to Diseases
to Sheath Blightto Sheath Blight

44. SymptomsSymptoms of rice sheath blight
Sheath blight has become increasingly
important because more fertilizers are being
used and also because of the use new high-
yielding cultivars which have large numbers
of tillers, resulting in an increase in the
humidity of plant layer.

45. Infection
Re-infection
Spread
Symptom
emergence
Sclerotia floating on water
may be carried away or drift off
and finally come in contact with
a rice plant, and then germinate
Infection: the mycelium often grows from
the outer surface of the sheath, taking
a round-about way through the edge
of the sheath, to the inner surface
Disease cycle of rice sheath blight
Survive in soil over winter as
scerotia or as mycelium in diseased plants
Spread

46. Inoculation method 1Inoculation method 1
The test populations are drill-seeded
in three-row plots with 18 cm between
rows and between plots. The plots are
inoculated approximately 60 days
after planting by broadcasting 100ml
per plot of a 2:1 (V:V) mixture of rice
hulls and un-hulled grains infested
with the pathogens.with the pathogens.
Preparation of Inoculum
Isolate is Incubated in sterile
mixture of rice hulls and un-
hulled grains at 28 ℃℃℃℃ for 3-5
days.

47. Inoculation method 2Inoculation method 2
Inoculation was carried out with short woody
toothpicks with a length of 0.8~1.0cm,
autoclaved toothpicks were incubated with RH-
9 strain on PDA medium for 2-3 days, then
placed behind the leaf collar of the third sheath,
counting from the top, at the first stem
elongation stage of growth.

48. AssessmentAssessment
6
5.5
5
4.5
7
6.5
8
7.5
8.5
6
5.5
5
4.5
7
6.5
8
7.5
8.5
Investigating the disease index the about 25 days after heading.
0 No infection observed
1 Lesion limited to lower 20% of the
plant height
3 20-30%
1
2
3
4
4.5
3.5
1
2
3
4
4.5
3.5
Scale:
Based on the reaching position of the lesion
0: No infection observed
5 31-45%
7 46-65%
9 More than 65%
Scale (IRRI):
Based on relative lesion height

49. Technique of Screening RiceTechnique of Screening Rice
Resistance to Bacterial Leaf BlightResistance to Bacterial Leaf Blight
Methods of Screening Rice Resistance to Diseases
Resistance to Bacterial Leaf BlightResistance to Bacterial Leaf Blight

50. Symptoms: Lesions usually start neat the leaf tips or leaf margins or both, and
extend down the outer edge(s). Yong lesions are pale green to grayish green, later
turning yellow to gray (dead) with time. In very susceptible varieties, lesions may
extend to the entire leaf length into the leaf sheath. Kresek or seedling blight caused
wilting and death of the plants.

51. SusceptibleSusceptible
cultivarcultivar
ResistantResistant
cultivarcultivar

52. Re-infectionSpread by
wind and rain
Infection
Symptom
emergence
Invade through water
pores on the leaf blade,
growth cracks and wounds
Xanthomonas oryzae pv. oryzae Spread
The organism survives on diseased
seed, straw and weed
Disease cycle of rice blastDisease cycle of rice bacterial leaf blight

53. Races ofRaces of XooXoo and differentiation NILs used in IRRIand differentiation NILs used in IRRI

54. 15
20
25
30
Hua 564
Hua 565
Wanxian 763
Wanxian 77
Huanghuazhan
Hexi 41
Yunjing 23
SAGC-4
SAGC-7
Zhonghua 1
Weed Tolerant Rice 1
Wuyujing 3
Wuyujing 20
Bacterialblightlesionlength(cm)
Resistant
Susceptible
0
5
10
0 5 10 15
Blast (%DLA)
053A-3
BD007
Cau 1
Cau 2
Yundao 1
Luyin 46
RC8
6527
JH15-1-1-1
PD29
D4098
Resistant
Susceptible
Bacterialblightlesionlength(cm)
Vera Cruz IRRI 2011

55. PhenotypingPhenotyping of rice BB in screening housesof rice BB in screening houses
Activities Time
germination test of seeds 3 days
Germination, incubated in 25 ℃℃℃℃ 2 days
sowing 50 seeds, 3reps, kept in greenhouse 7-8 days
transplant to screen house 40 days
prepare Xoo, in 28℃℃℃℃ 6 days
inoculation, in screen house 14 days
scoring 1 day
Totally 68 days

56. Preparation of Isolates
stocks Methods Condition Tempera
ture (℃℃℃℃)
Time
A 3-day-old
slant
5 2 months
(temporary)
Storage methods forStorage methods for XooXoo
slant (temporary)
B Lyophiliz
ed stock
5 Long term
C Skmilk
(nonfat)
-20 5 years
D Glycerol
(30%)
-70 - -80 10-20 years
On PSA at 28 ℃℃℃℃for 2-3 day

57. Media forMedia for XooXoo
A , WAKIMOTO’S MEDIM-
Modified (WF-P)
Sucrose 20g
Peptone 5g
Calcium Nitrate 0.5g
Sodium Phosphate 0.75g
Ferrous Sulfate 0.05g
Agar 17g
C, SUWAS’S MEDIUM
Sodium Glutamate 2g
MgCl2.6H2O 1g
KH2PO4 0.1g
Peptone 10g
Sucrose 5g
Agar 17g
Distilled Water 1000ml
Fe-EDTA *SS 1ml
Stock Solution=0.657g/100ml
Distilled Water 1000ml
B, PEPTONE SUCROSE AGAR
(PSA)
Peptone 10g
Sucrose 10g
Sodium Glutamate 1g
Agar 17g
Distilled Water 1000ml
D, XOS MEDIUM
Monosodium Glutamate 5g
Ca(NO3)2 1g
K2HPO4 2g
Peptone 2g
Sucrose 20g
Agar 17g
Distilled Water 1000ml
Fe-EDTA 1mg
PH- 6.8-7.0

58. Preparing the plants for inoculationPreparing the plants for inoculation
In a screening house
Clipping methodClipping method
In a green-house
Cut upper portion of
the leaf using sterile
scissor dipped on
bacterial suspension
(107-8/ml)
Two weeks after inoculation

59. AssessmentAssessment
Scale
(for greenhouse test, lesion area)
1 0-3%
2 4-6%
3 7-12%
4 13-25%
5 26-50%
Scale
(for field test, lesion area)
1 1-5%
3 6-12%5 26-50%
6 51-75%
7 76-87%
8 88-94%
9 95-100%
3 6-12%
5 13-25%
7 26-50%
9 51-100%
Note: In both seedling and fields tests, folded young leaves should not be
inoculated. Old or leaves with symptom of nutrient deficiency or other
diseases should also be avoided for inoculation.

60. Population Cross Donor
Gen.
Number of lines
(10
DS)
HHZ5 Huang-Hua-Zhan*2/OM1723 OM1723 BC1F5 75
HHZ8 Huang-Hua-Zhan*2/Phalguna Phalguna BC1F5 56
HHZ9 Huang-Hua-Zhan*2/IR50 IR50 BC1F5 62
HHZ11 Huang-Hua-Zhan*2/IR64 IR64 BC1F5 56
Materials evaluated for blast and bacterial blight resistance
HHZ12 Huang-Hua-Zhan*2/Teqing Teqing BC1F5 66
HHZ15 Huang-Hua-Zhan*2/PSBRC66 PSBRc66 BC1F5 45
HHZ17 Huang-Hua-Zhan*2/CDR22 CDR22 BC1F5 70
HHZ19 Huang-Hua-Zhan*2/PSBRC28 PSBRc28 BC1F5 82
by Dr. Xu in 2010-2011

61. 10
15
20
25
30
PXO 61
PXO 86
PXO 79
PXO 340
PXO 71
PXO 112
PXO 99
PXO 145
PXO 280
PXO 339
PXO 341
PXO 347
0
5 PXO 349
PXO 363
Interaction among 14 Xoo strains and selected lines in HHZ15 population.

62. Blast evaluation of virulent strainsBlast evaluation of virulent strains
Evaluation of BB resistance of >500 lines (HHZ background) against 14 strains of 10Evaluation of BB resistance of >500 lines (HHZ background) against 14 strains of 10 XooXoo races, 2010 WSraces, 2010 WS
HHZ PSBRc66 BC1F5 # 329 BC1F5 #350
Meirong Xu et al

63. ◇◇◇◇ Rice diseases caused by viruses and
mycoplasma- like organism (MLO)
Screening Rice Resistance to Virus
Diseases
◇◇◇◇◇◇◇◇ Rice Tungro Disease (RTD)Rice Tungro Disease (RTD)
mycoplasma- like organism (MLO)

64. Rice disease caused by viruses andRice disease caused by viruses and
mycoplasmamycoplasma--like organism (MLO)like organism (MLO)
The reaction of a certain genotype to rice virus
infection can be assessed by a skilled worker based
on visible symptoms after inoculation under natural
conditions (in a field), or under controlled conditionsconditions (in a field), or under controlled conditions
(in a greenhouse).
The factors needed for a successful test are the
presence of virus sources and insect vectors,
inoculation at the susceptible growth stage of the test
plants and favorable environmental conditions.

65. Field test:Field test:
Screening of test materials, notably breeding lines, can
be done in the fields and their reaction to virus
infection can be assessed on a scale 0-9 based on the
percentage of infection observed.
Scale (% infection)
0 No symptom observed0 No symptom observed
1 1-10%
3 11-30%
5 31-50%
7 51-70%
9 71-100%
However, field tests generally select vector resistance
and are not appropriate for selecting virus resistance.

66. Greenhouse test:Greenhouse test:
Resistance to the virus can be assessed in the
greenhouse where factors needed for infection
can be manipulated. Inoculation using a high
number of vectors is desired and the
susceptible check should have at least 90% ofsusceptible check should have at least 90% of
infection.
A healthy check would be also useful as a
reference to measure plant height. Since some
fertilizers might affect symptoms, it is
recommended not to use any during the
experiment.

67. Disease index (DI)Disease index (DI)
A disease index (DI) for the genotype, which would
represent both disease incidence and symptom severity,
can be used as an indicator foe virus resistance in a
greenhouse test. DI can be calculated as:
DI =
n (3)+ n (5)+ n (7)+ n (9)
tn
Where n (3), n (5), n (7), and n (9) = number of plants showing a
reaction in scale;
tn = total number of plants scored

68. The resulting DI can be classified as:The resulting DI can be classified as:
DI Reaction
0-3 Resistant/Tolerant
4-6 Moderate
7-9 Susceptible
For further confirmation, test materials with DI rating of
0-3 may be tested by forced inoculation using different
number of vectors, at different plant growth stages, and
may be assayed serologically to differentiate between virus
resistance/tolerance or insect (vector) resistance.

69. Rice Tungro Disease (RTD)Rice Tungro Disease (RTD)
Causal agents: Rice tungro bacilliform virus (RTBV) and rice
tungro spherical virus (RTSV)
Symptoms: Yellow to yellow orange leaves, stunting, and slightly
reduced tillering.
At growth stages (IRRI):
2 (for the GH)
3-5 (for the field)

70. Scale of RTDScale of RTD
1 no symptom observed
3 1-10% height reduction, no distinct yellow to
yellow orange leaf discoloration
5 11-30% height reduction, no distinct yellow to
yellow orange leaf discoloration
7 31-50% height reduction, with distinct yellow to
yellow orange leaf discoloration
9 More than 50% height reduction, with distinct
yellow to yellow orange leaf discoloration

71. Discussion on genetic studies of
host plant-pathogen interactions

72. Disease reactions of the parents, IR64, Teqing and their
introgression lines (ILs) and 75 Teqing ILs to 10 Philippine
Xanthomonas oryzae pv oryzae (Xoo) races that cause bacterial
leaf blight (BLB) in rice
Xoo races IR64 Teqing Binam IR64 ILs Teqing ILs
Race 1 R a MS S R S
Race 2 S S S S S
Race 3 S S S R SRace 3 S S S R S
Race 4 MS S S R MS
Race 5 MR MR S MR MS
Race 6 S S S R/S b S
Race 7 MR R S MR S
Race 8 R R MS R S
Race 9 S R MR R/S b R
Race 10 R R S R MS

74. R
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RM600(1.5)
RM525(2.8)
RM50(6.3)
RM6(2.9)
RM10916(?)
RM55(3.9)
RM411(3.8)
IR64
Binam
S
S
S
S
S
S
33
35
36
50
66
5
7
1
78
34
37
77
38
13
46
73
2
15
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Race3
Race4
Race6
ILs
95
90
89
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S R
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17
39
93
84
18
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8
68
4
42
25
21
45
23
55
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IR64
Binam
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R
RM55(3.9)
RM600(1.5)
RM525(2.8)
RM50(6.3)
RM6(2.9)
RM10916(?)
RM411(3.8)
Race3
Race4
Race6
ILs
Graphic presentation of the genotypes of 99 IR64 ILs at 7 loci
associated with resistance to Xoo races 3, 4, and 6.
R
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19
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24
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57
62
72
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44
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26
61
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51
27
64
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87
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55
81
91
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47
32
69
85
94
56
10
58
6
22
52
86
12
92
49
11
60
40
28
29
3
14
98
79
48
30
40
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R

75. Conclusion remarksConclusion remarks
Appropriate screening methods are essential
for identifying resistant plants from a
segregating population;
Screening resistance to airborne fungal
diseases and/or race specific bacterialdiseases and/or race specific bacterial
diseases requires use of multiple
races/isolates and/or evaluation in multiple
sites under natural disease hotspots;
Scoring for reactions to race-specific
diseases should include both qualitative and
quantitative measurements

76. Screening for BPH Resistance
IR64

77. *A total of 193 BC2F2 populations was screened for BPH
resistance using the BPH screening facility at IRRI.
*One hundred pre-germinated seeds per BC2F2 bulk were sown in
plastic trays (40 cm 60 cm) half-filled with garden soil
along with TN1 (susceptible check) and RPs.
*Ten days after sowing, each seedling was infested with two 2nd to
PROTOCOL
*Ten days after sowing, each seedling was infested with two 2nd to
3rd instar nymphs using the local BPH population.
*The plastic insect cage was installed on each tray to contain the
insect population.
*When TN1 and RPs were killed, surviving plants
from each BC2F2 population were counted and transferred to
the field.

78. Summary results of BC populations screened for brown planthopper
resistance
Details Brown planthopper resistance
IR64 TQ NPT Total
Total BC2F2 populations 64 67 62 193
Single plant selections per BC
population 0 - 22 0 - 22 0 - 2
Total selected BC2F3 lines 652 255 2 909
Selection intensity (%) 10.19 3.81 0.03 4.71
Number of indica donors 49 60 49 158
Selected lines 565 221 2 788
Selection intensity (%) 11.53 3.68 0.04 4.99
Number of japonica donors 9 11 7 27
Selected lines 54 21 0 75
Selection intensity (%) 6.00 1.91 0.00 2.78
Number of intermediate
donors 4 3 3 10
Selected lines 33 2 0 35
Selection intensity (%) 8.25 0.67 0.00 3.50
For individual BC populations of 100 plants, a difference of 2.5% between two populations in selection
intensity (survival rate) is statistically significant at P < 0.05 when the selection intensity is < 0.1.

79. # of BC2F2 pop. 64 74 62 200
BHP resistance
IR64 Teqing NPT Total
Summary results of BC populations for screening
for BPH resistance
# of selections per pop. 0 - 22 0 - 22 0 - 2
Total selected lines 652 255 2 909
# of contributing
donors 62 67 59 189
SI (%) 10.19 3.81 0.03 4.71
For individual BC populations of 200 plants, a difference of 4% between two populations in
selection intensity (survival rate) is statistically significant at P < 0.05 when the selection
intensity is between 0.1 and 0.5.

80. Ragged stunt virus-BPH outbreak in Sukamandi, Indonesia Ragged stunt virus-BPH –Tolerant inbred lines
Promising Multiple disease resistant GSR hybrids at Jakenan rainfed conditions DS2010

81. Zhongzu14-ski-4-1

82. BPH and Virus Resistance Screening
IRRI-ICRR joint project collaborators: Prof.Baehaki/Drs Muhsin,Untung
• 30 BC3F2 and BC2F3 population (CS 3)
• 39 BC3F3 and BC2F4 population (CS 4; 3rd
year)ongoing
BC2 F3 HHZ populations screened against virulent
BPH strain that caused outbreak in Sukamandi in 2010
Several populations showed ILs with comparable
resistance with the checks in second round of
screening.
ICRR 8.2011