IJERD – International Journal of Environmental and Rural Development (2020) 11-2

Research article
erd

Reaction of Different Rice Varieties to Bacterial Blight
HAN SU YIN*
Yezin Agricultural University, Yezin, Nay Pyi Taw, Myanmar
Email: hsyyau@gmail.com

SEINT SAN AYE
Yezin Agricultural University, Yezin, Nay Pyi Taw, Myanmar

HTAY HTAY OO
Yezin Agricultural University, Yezin, Nay Pyi Taw, Myanmar

YI YI MON
Yezin Agricultural University, Yezin, Nay Pyi Taw, Myanmar

TIN AYE AYE NAING
Yezin Agricultural University, Yezin, Nay Pyi Taw, Myanmar
Received 20 January 2020

Accepted 5 December 2020(*Corresponding Author)

Abstract Rice is the major food crop in Myanmar and bacterial blight is one of thedevastating diseases affecting production. In this study, 37 local rice varieties and 41 ricelines were tested at Yezin Agricultural University, Myanmar, to three different isolates of
Xanthomonas oryzae pv. oryzae to evaluate the resistance levels of these different rice
varieties. The three bacterial isolates used in this experiment were collected from Zeyathiri,
Zabuthiri and Pyinmana townships in Nay Pyi Taw Union Territory. At maximum tillering
stage, the uppermost fully expanded leaves were inoculated by the clipping method. Three
weeks after the inoculation, the percent leaf area of the inoculated leaves was visuallyestimated and the disease reaction of the rice varieties determined. The thirty-seven local rice
varieties were classified into seven groups, with this grouping based on the reaction patterns
to the three isolates. Group VII, which contained two varieties, Nga Sar Kay and Sinthukha,
was moderately resistant to Pyinmana isolate and moderately susceptible to the Zeyathiri and
Zabuthiri isolates. The rice varieties included in Group I to Group VI showed susceptible
reactions to testing with all three isolates. Among YAU rice lines tested, YAU-1211-71-1-1
exhibited moderate resistance to the Pyinmana isolate only. Apart from the line mentioned
above, all the other YAU rice lines, did not exhibit resistance reactions to the test isolates.
Nga Sar Kay, a local rice variety, has the potential to be used in the future rice breeding
programs and YAU-1211-71-1-1 is the promising one to be used in areas where rice bacterial
blight disease is prevalent.
Keywords bacterial blight, resistant varieties, rice, Xanthomonas oryzae pv. oryzae

INTRODUCTION
Rice (Oryza sativa L.) is the most widely eaten staple food crop, especially in Asia, and is consumed
by more than half the world’s population. Unfortunately, rice crops are threatened by a considerable
number of diseases (more than 40 diseases) of fungal, bacterial and viral origin, and these diminish
rice yields throughout the world (Singh et al., 2013). Among rice diseases, bacterial leaf blight (BLB)
caused by Xanthomonas oryzae pv. oryzae (Ishiyama) (Swings et al., 1990) is one of the mostdestructive and widespread diseases of rice. In Myanmar, bacterial blight is also one of the mostserious diseases present, and every year, its occurrence has been reported from the different rice
growing regions throughout the country (Lwin, 2006). Higher losses are common in tropical Asian
countries, such as Myanmar, because of the prevalence of virulent pathogen populations and theⒸ ISERD

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susceptibility of the high yielding cultivars in tropical area (Aye et al., 2007). Yield losses due to thedisease are estimated to range from 0.5% to 50% (Myint et al., 1983; Win, 2013).
Many control strategies, including various cultural practices, application of various chemicals
and systematic use of chemical fertilizers have been attempted in an effort to control bacterial blightdisease, but these management tactics have not been very effective. Although chemical control plays
an important part in an integrated disease management program, it has a detrimental effect on humanhealth and non-target, beneficial microorganisms. Non-systematic use of agricultural chemicals canalso contribute to the emergence of new races of the pathogen and ultimately prove a waste of money
for resource limited farmers. The most feasible, effective and economical way of controlling bacterial
blight in Myanmar, is the exploitation of the host plant resistance. Moreover, use of resistant varietiesis also compatible with other disease control methods. Although research on varietal resistance isconducted irregularly in Myanmar, varietal resistance is probably the most important area to focus
on for effective disease management.
OBJECTIVE
This study was conducted to evaluate the resistance levels of different rice varieties and lines to
Xanthomonas oryzae pv. oryzae.
METHODOLOGY
Test Varieties and Preparation of Plants
Thirty-five local rice varieties, and 41 YAU rice lines were used in this study. Manawthukha wasused as a ‘susceptible’ control and Sinthukha was used as a ‘resistance’ control variety. Seeds ofthese rice varieties were obtained from the Department of Plant Breeding, Physiology and Ecology,
Yezin Agricultural University. Firstly, rice seeds were sterilized in hot water at 56 ˚C for 15 minutes
and germination accomplished using the paper towel method. Germinated seeds were sown in 20 cm
× 20 cm plastic pots containing sterilized soil, and twenty- one day old seedlings of each of the test
varieties were transplanted individually in plastic pots, containing 3 kg of lowland soil, and thesewere watered as necessary. Fertilizer application was carried out according to the standard methodsof managing rice plants.
Bacterial Isolates
Three very virulent isolates (Isolate I, Isolate II and Isolate III which were collected from Zeyathiri,
Zabuthiri and Pyinmana townships in Nay Pyi Taw Union Territory) of Xanthomonas oryzae pv.
oryzae were used for inoculation in this experiment.
Inoculum Preparation and Inoculation
Isolates from preserved tubes were sub-cultured on peptone sucrose agar (PSA) (Tsuchiya et al.,1982) medium plates and incubated for two days. The bacterial suspension was prepared bysuspending the bacterial mass from PSA plates in sterilized distilled water and adjusted to 108 cfu/ml
using a Thermo Scientific Evolution 201 Uv-Visible Spectrophotometer. In order to distinguish the
inoculated isolates, plants in a pot were bundled into three groups by labelling with different coloredties (Aye et al., 2007). Inoculation was done at maximum tillering stage, by clipping the uppermost
fully expanded leaves of five tillers 2-3 cm from the leaf tips with a pre-sterilized pair of scissors,which were then dipped in the bacterial suspension (Kauffman et al., 1973).
Disease Assessment and Data AnalysisⒸ ISERD

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Percent leaf area infected on inoculated leaves were visually estimated 21 days after inoculation.
Disease reaction of the rice varieties to the bacterial isolates were determined based on the diseasescores (IRRI 1988) (Table 1).
Table 1 Standard Evaluation System for Rice (for bacterial blight) (IRRI, 1988)% Leaf area infected

Score scales

Description

1-5

1

R

6-12

3

MR

13-25

5

MS

26-50

7

S

>50
9
HS
R: Resistant, MR: Moderately resistant, MS: Moderately susceptible, S: Susceptible, HS: Highly susceptible

RESULTS AND DISCUSSION
Reaction of Myanmar Local Rice Varieties
Thirty-seven Myanmar local rice varieties were evaluated for their reaction to three isolates of
Xanthomonas oryzae pv. oryzae. Based on the reaction patterns to these three isolates, 37 rice
varieties were characterized into seven varietal groups, Group I-VII is shown in Table 2. Thirteen
Myanmar local rice varieties belonging to Group I were highly susceptible to Isolate I and Isolate II,
and susceptible to Isolate III. Group II consists of seven rice varieties, which showed moderate
susceptibility to Isolate III and were high susceptibility to Isolates I and Isolate II. In Group III, Khao
Phee Phan and Thiri Done Pathein were highly susceptible to Isolate I, susceptible to Isolate II andmoderately susceptible to Isolate III. Only one variety, Kauk Kyi Shan Ma, showed the same reaction(susceptible) to all three test isolates. Three varieties in Group V were susceptible to Isolate I, highly
susceptible to Isolate II and moderately susceptible to Isolate III. Bacterial isolates I, II and III werevirulent to all plants in Group VI, including the nine rice varieties which presented susceptible
reactions to Isolate I and II and moderately susceptible reactions to Isolate III. Two varieties, namely
Nga Sar Kay and Sinthukha, belonging to Group VII, exhibited a moderate resistance reaction to
Isolate III and a moderate susceptible reaction to Isolates I and II.
Reaction of Yezin Agricultural University (YAU) Rice Lines
Forty-one varieties of YAU’s promising rice lines were also tested for their response to these threeisolates of Xanthomonas oryzae pv. oryzae. According to disease severity, these YAU rice lines wereclassified into eight groups, Group I-VIII is shown in Table 3. Group I include only the Manawthukha
variety, which was highly susceptible to all test isolates. In Group II, three YAU lines showed highly
susceptible reactions to bacterial Isolates I and II and a susceptible reaction to Isolate III. The threerice lines included in Group III expressed highly susceptible reactions to Isolate II and susceptible
reactions to Isolates I and III. In Group IV, YAU-1201-90-2-2 showed the same reactions to Isolate
I and II as in Group III but it displayed a moderately susceptible reaction to Isolate III. The twelve
rice lines that belonged to Group V were susceptible to all test isolates. Group VI included nineteen
tested lines and they were susceptible to Isolates I and II and moderately susceptible to Isolate III.
Two rice lines in Group VII, YAU-1211-116-3-3 and YAU-1211-223-3-2, presented moderately
susceptible reactions to the three test isolates. The lowest disease severity values were found in thevarieties YAU-1211-71-1-1 and Sinthukha, which belong to Group VIII. Compared to other test
varieties, these rated as moderately resistant to Isolate III and moderately susceptible to Isolate I and II.
In the evaluation of the reaction of rice varieties, almost all of the local rice varieties showedsusceptible reactions to the three test isolates. Of the 37 Myanmar rice varieties, Nga Sar Kay and
Sinthukha, expressed a moderate resistance reaction to Isolate III (Pyinmana) only. This result
indicates that these varieties may harbor a gene resistant to Isolate III and so might be useful forⒸ ISERD

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further rice breeding program. In the present study, Sinthukha was moderately susceptible to two
isolates (Isolate I and II). Although Xa21 was used as a broad-spectrum resistance gene (Khush etal., 1990) in its breeding program, the Sinthukha variety which contains the Xa21 gene, showed amoderately susceptible reaction to two isolates. A similar result was observed by Swamy et al.,(2006) who reported that Pusa Basmati 1 and its transgenic derivative PB-Xa21 were much more
susceptible to virulent Mxo isolates than IRBB 21. The present finding is in conformity with theresults of (Myint, 2008) and (Maung, 2014) who reported that Sinthukha was susceptible to a test
isolate which showed a resistant reaction to IRBB 21.
Table 2 Reaction of thirty-seven rice varieties to three most virulent isolates of Xanthomonas
oryzae pv. oryzae
Sr. No.

Name of local varieties

Disease reaction and Disease severity (%) to bacterial isolate
Isolate I
Isolate II
Isolate III( Zeyathiri)( Zabuthiri)(Pyinmana)

Group I
1
Boke Thwin Phyu
HS (72)HS (84)
S (43)
2
Khao LinHS (59)HS (56)
S (26)
3
Muyinn Saba
HS (63)HS (72)S (30)
4
Yoe WaHS (53)HS (63)S (29)
5
V15
HS (60)HS (71)S (30)
6
Bu ToylHS (56)
HS (72)S (30)
7
Khun Na Yar Po
HS (63)HS (67)
S (27)
8
Sa WanaHS (66)HS (90)S (28)
9
Japan Ni
HS (73)HS (66)
S (41)
10
Khao Mae Pan
HS (59)HS (70)S (29)
11
Lone Phyu
HS (55)HS (84)S (30)
12
Sa Bong Thaw
HS (72)HS (86)
S (31)
13
Manawthukha
HS (73)HS (71)S (49)
Group II
14
Ant Paw
HS (59)HS (64)
MS (24)15
Khao Pi Paung
HS (55)HS (54)
MS (24)
16
Thu Kha-2
HS (55)HS (67)MS (24)17
Tayote Hmwe
HS (59)HS (67)MS (25)18
Shal Thu Kha
HS (54)HS (66)
MS (24)19
Aye Yar Padae Thar
HS (54)HS (67)MS (24)20
Shwe Thwe Yin
HS (51)HS (60)MS (24)
Group III
21
Khao Phee Phan
HS (51)S (49)
MS (19)22
Thiri Done Pathein
HS (52)S (50)
MS (24)
Group IV
23
Kauk Kyi Shan Ma
S (47)S (44)S (26)
Group V
24
Kauk Kyi
S (48)HS (60)MS (17)25
Khao Kham To
S (39)HS (64)
MS (22)26
Shwe War Yin
S (34)
HS (55)MS (14)
Group VI27
Paw (1)S (50)S (50)
MS (25)28
Paw San Hmwe
S (36)S (39)
MS (21)29
Khao Lamil
S (42)S (45)
MS (17)30
Naung Ta Moe Se
S (46)S (48)
MS (21)
31
Kun Lone
S (48)S (47)
MS (25)32
Hmaw Bi Kyauk Nyin Hmwe
S (42)S (27)
MS (21)33
IR 36
S (43)S (34)
MS (18)34
Ma Naw Tun
S (50)S (39)
MS (20)35
Bu Aung Ban
S (48)S (45)
MS (23)
Group VII36
Nga Sar Kay
MS (19)MS (24)MR (10)37
Sinthukha
MS (16)MS (14)MR ( 8 )Sr. No.: Serial number, MR: Moderately resistant, MS: Moderately susceptible, S: Susceptible, HS: Highly susceptibleⒸ ISERD112

IJERD – International Journal of Environmental and Rural Development (2020) 11-2

Table 3 Reaction of forty-one YAU rice lines and two check varieties to three most virulent
isolates of Xanthomonas oryzae pv. oryzae
Sr. No.

Name of YAU rice lines

Disease reaction and Disease severity (%) to bacterial isolate
Isolate I
Isolate II
Isolate III( Zeyathiri)( Zabuthiri)(Pyinmana)

Group I
1
Manawthukha
HS (84)HS (90)HS (81)
Group II2
YAU-1214-B-B-B-153-3-1
HS (52)HS (66)
S (33)3
YAU-1214-183-3-4-1-1-1
HS (54)HS (68)S (36)4
YAU-1215-S- S- S-77- 2-1
HS (52)HS (66)
S (30)
Group III5
YAU-1201-187-1-2
S (44)
HS (56)
S (26)6
YAU-1201-1-2-1
S (39)
HS (53)S (26)7
YAU-1211-223-3-1
S (39)
HS (72)S (28)
Group IV8
YAU-1201-90-2-2
S (40)
HS (54)
MS (23)
Group V9
YAU-1201-179-2-1
S (39)S (43)S (32)10
YAU-1211-22-2-1
S (34)S (48)S (27)11
YAU-1211-118-1-1
S (40)S (48)S (28)12
YAU-1211-211-2-1
S (31)S (45)S (29)13
YAU-1214-S-S-S-77-1-1
S (36)S (44)S (26)14
YAU-1215-B-B-B-139-3-1
S (41)S (42)S (31)15
YAU-1215-B-B-B-153-3-1
S (41)S (43)S (27)16
YAU-1214-183-3-1-2-1-1
S (35)S (42)S (31)17
YAU-1214-183-3-3-1-1-1
S (38)S (42)S (28)18
YAU-1214-183-35-1-1-1-1
S (30)S (38)S (26)19
YAU-1215-73-2-3-1-1-1
S (39)S (41)S (29)20
YAU-1215-B-B-B-168-1-1
S (39)S (43)S (27)
Group VI21
YAU-1215-S-S-S-40-2-1
S (36)S (49)
MS (20)22
YAU-1215-S-S-S-41-1-1
S (29)S (37)
MS (23)23
YAU-1215-S-S-S-55-2-1
S (30)S (34)
MS (21)
24
YAU-1215-B-B-B-10-1-1
S (31)S (41)
MS (17)25
YAU-1201-61-3-3
S (27)S (32)
MS (19)26
YAU-1201-90-2-4
S (32)S (37)
MS (25)27
YAU-1201-121-3-1
S (36)S (42)
MS (24)28
YAU-1201-202-1-2
S (30)S (28)
MS (21)
29
YAU-1201-202-2-2
S (34)S (41)
MS (24)30
YAU-1201-202-2-1
S (38)S (34)
MS (22)
31
YAU-1211-20-1-1
S (33)S (40)
MS (20)32
YAU-1211-54-2-1
S (26)S (32)
MS (22)
33
YAU-1211-95-2-1
S (28)S (31)
MS (19)34
YAU-1211-116-3-4
S (33)S (44)
MS (23)35
YAU-1211-118-2-1
S (35)S (44)
MS (18)36
YAU-1211-154-3-1
S (35)S (41)
MS (25)37
YAU-1211-179-3-2
S (32)S (31)
MS (22)
38
YAU-1214-183-3-1-1-1-1
S (30)S (39)
MS (22)
39
YAU-1215-80-1-2-1-1-1
S (27)S (29)
MS (22)
Group VII40
YAU-1211-116-3-3
MS (19)MS (25)MS (13)
41
YAU-1211-223-3-2
MS (25)MS (21)
MS (14)
Group VIII42
YAU-1211-71-1-1
MS (19)MS (24)MR (11)43
Sinthukha
MS (17)MS (18)MR (12)
Sr. No.: Serial Number, MR: Moderately Resistant, MS: Moderately Susceptible, S: Susceptible, HS: Highly Susceptible

As mentioned, in this study, all YAU rice lines except YAU-1211-71-1-1 displayed moderately
susceptible to highly susceptible reactions and rice lines differed in reaction with different isolatesof the pathogen. The present study reached similar conclusions to Noor et al., (2006), who stated that
the Xanthomonas oryzae pv. oryzae strains which induced a susceptible reaction in one variety ofⒸ ISERD

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rice, are not necessarily able to induce similar reaction in other varieties. YAU-1211-71-1-1 andSinthukha varieties showed moderate resistance to isolate III (Pyinmana) in the present study. The
YAU-1211-71-1-1 may also contain a resistance gene (Xa21) because it was developed from a crossof Sinthukha, a popular variety which is resistant to bacterial blight disease (and as mentioned, carries
the resistance gene Xa21), and Long 8, a hybrid rice variety which is high yielding.
CONCLUSION
The Nga Sar Kay and Sinthukha rice varieties and YAU-1211-71-1-1 rice line are moderately
resistant to Isolate III (Pyinmana). Nga Sar Kay, considered as a Myanmar local variety, has potential
to be used in future rice breeding program. Also Sinthukha and YAU-1211-71-1-1 show goodpotential for use in disease prone areas, especially in combination with other management practices.
The YAU-1211-71-1-1 can be considered as a promising rice line that could be grown in bacterial
blight prone areas, again in combination with other management practices. The emergence of a newrace is responsible for the removal of many resistant varieties according to the gene-for-gene concept.
Therefore, further research such as the investigation of new strains that have arisen in nature and thescreening of rice varieties for their resistance or/ susceptibility to that race, need to be constantly andfrequently undertaken in the future.
ACKNOWLEDGEMENTS
We acknowledge the financial support provided by YAU-JICA Technical Cooperation Project,
Yezin, Nay Pyi Taw, Myanmar.
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