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Sarhad J. Agric. Vol. 24, No.1, 2008
CHARACTERIZATION OF WILD RICE SPECIES IN RESPONSE
TO LEAFFOLDER Cnaphalocrocis medinalis
Syed Mehar Ali Shah*, Hidayat-ur-Rahman*, Abdul Rehman**, Fida Muhammad
Abassi**, Ifthikhar Hussain Khalil* and Asad Ali***
ABSTRACT
The rice leaffolder, Cnaphalocrocis medinalis (Gn) attained the status of major pest during the last few years in major rice
growing areas of the world. To search for possible sources of resistance against leaffolder, an experiment comprising 14 species
of wild rice (Oryza sp.), three extensively cultivated varieties of rice in Pakistan together with one susceptible check of cultivated
rice was conducted in the greenhouse of National Agricultural Research Centre, Islamabad during 2005. Most of the tested wild
species and the three cultivated varieties showed susceptibility to leaffolder. O. australiensis was highly susceptible to leaffolder
with maximum damage rating score of 9 and highest percent infestation of 56.6. O. alta, O. barthii, O. grandiglumis, O.
glumaepatula, O. latifolia, O. longistaminata, O. nivara, O. officinalis, O. punctata and O. rhizomatis gave damage rating score
of 5 and were moderately susceptible to leaffolder. However, two wild species, O. brachyantha and O. rufipogon were found
resistant to leaffolder with damage rating scale of 1. O. brachyantha and O. rufipogon showed low percent infestation values of
3.7 and 5.26, respectively. Whereas, O. meridionalis expressed moderate level of resistance with damage rating score of 3. Of the
cultivated varieties used in the present study, Bas-385 and KSK-282 were found susceptible to this pest, with damage rating score
of 7 while IR-6 was moderately susceptible with damage rating scale of 5. The use of these resistant wild species via
hybridization program is, therefore, suggested to incorporate resistance genes to cultivated rice and to develop rice cultivars
resistant to this major insect pest.
Keywords: Rice leaffolder, Cnaphalocrocis medinalis (Gn), characterization, response, screening, Oryza species, wild rice
species, cultivated rice
INTRODUCTION
The rice leaffolder, Cnaphalocrocis medinalis (Gn)
was considered a minor and sporadic insect pest of
rice in Asian countries including Pakistan. It has,
however, attained the status of major pest during the
last few years. Several outbreaks of the pest have
been reported in Bangladesh, China, Japan, Fiji,
India, Korea, Malaysia, Nepal, Philippines, Sri Lanka
and Vietnam (Wada et al., 1980 and Khan et al.,
1988). In Pakistan, this pest has multiplied
enormously, with severe incidence observed during
the August-September 1980-90 crop year. Overall
leaf infestation during the same year was 25%,
reducing 30% grain yield in major rice growing areas
of the Punjab. While, at some locations the
infestation was as high as 50% (Salim et al., 1991).
Changes in physical factors of environment, cultural
practices, multiple cropping patterns, reduced genetic
variability of improved high yielding cultivars,
application of high levels of nitrogenous fertilizers
and prophylactic use of pesticides are reported to be
the major reasons of leaffolder infestation (Khan et
al., 1989). In Pakistan, the application of insecticides
is the most common approach for controlling
leaffolder. Overdependence on insecticides is usually
not a preferred and sustainable pest control strategy
as it results in development of the insecticide
resistance in insects, destruction of bio-control
agents, resurgence of target pests, outbreak of
secondary pests, environmental pollution and food
products contamination (Rehman, 2001).
Development and use of resistant varieties can be a
better option to reduce dependence on insecticides
and ensure sustainable rice production. Locally
available rice germplasm has already been screened
against leaffolder under controlled conditions but
none of the cultivated rice variety was found resistant
(Ahmed et al., 2000 and Rehman, 2003). It is,
therefore, imperative to search resistant sources in
wild rice germplasm to develop rice varieties
resistant to leaffolder. Realizing the importance of
varietal resistance in insect control strategies, the
present study was, therefore, planned to screen wild
relatives of rice for a possible source of resistant
genes to leaffolder.
MATERIALS AND METHODS
The experiment was carried out in the greenhouse of
Plant Genetic Resources Institute (PGRI), National
Agricultural Centre (NARC), Islamabad during the
2005 rice crop growing season. Germplasm of 14
wild species of rice provided by International Rice
Genebank Collection (IRGC), International Rice
Research Institute (IRRI), Philippines, three widely
used cultivated varieties of rice in Pakistan viz. Bas-
385, IR-6 and KSK-282 along with one susceptible
check of cultivated rice, TN1 was used. The list of
wild rice species along with their IRGC accession
number and source is given in Table I. Seeding was
* Department of Plant Breeding and Genetics, NWFP Agricultural University, Peshawar – Pakistan.
** Rice Programme, Crop Sciences Institute, National Agricultural Centre, Islamabad – Pakistan.
*** Imperial College London, UK
Syed Mehar Ali Shah, et al. Characterization of wild rice species in response to lenffolder …… 70
done on sterilized petridishes. Seven days after
seeding, seedlings were transplanted into well
puddled pots having both length and diameter of 25
cm. To increase the number of plants, cloning of
wild relatives was done. Clones derived from the
newly arising tillers of existing plants were
subsequently transferred to well puddled pots. Each
clone later developed into full fledge plant. To get
larvae of uniform age for use in experiment, insects
were reared in laboratory under controlled conditions.
The procedure for screening of wild rice species was
adopted according to Henrichs et al. (1985). Ten
larvae of leaffolder were applied 50 days after
transplantation to each pot having three plants/clones.
The plants were caged to avoid external infestation
from other insects and also to prevent predation of
leaffolder larvae from bio-control agents. Seven days
after infestation, cages were removed to provide
natural conditions for better growth of plants. The
material was evaluated 21 days after infestation when
almost 60% leaves of susceptible check were
infested. For each wild species and cultivated
varieties, all the leaves including infested ones were
thoroughly examined. The number of damaged leaves
along with undamaged ones was recorded and
percent infestation was determined for wild species
and cultivated varieties using the following formula
% Infestation=Number of damaged leaves × 100
Total number of leaves
During thorough examination of the leaves, each leaf
was rated from 0-3 based on the extent of damage as
0= No damage, 1= Up to 1/3 of leaf area scrapped, 2=
1/3 to 1/2 of leaf area scrapped and 3= More than 1/2
of leaf area scrapped. Based on the number of leaves
with damage grade, % damage rating (R) was
computed for each rice genotype and susceptible
check as follows:
(Leaves with damage (Leaves with damage (Leaves with damage
R= grade of 1×100) 1 + grade of 2×100) 2+ grade of 3 × 100) 3 ÷ 6
Leaves observed Leaves observed Leaves observed
Adjusted % damage rating (D) was also determined
for each test genotype as given below:
D = R of test genotype × 100
R of susceptible check
The adjusted damage rating (D) was converted to a
0-9 scale as follows:
Scale % Adjusted Damage Rating (D) Status
0 0 Highly Resistant
1 1-10 Resistant
3 11-30 Moderately Resistant
5 31-50 Moderately Susceptible
7 51-75 Susceptible
9 More than 75 Highly Susceptible
RESULTS AND DISCUSSION
Fourteen species of wild rice, three extensively
cultivated rice varieties of Pakistan along with one
susceptible check of cultivated rice were screened
against leaffolder with the objective that wild species
of rice could carry resistant genes against this major
insect pest. In O. alta plants, the numbers of damaged
leaves were 20 out of 55 leaves, showing 36.36
percent infestation. On the basis of extent of damage,
out of these 20 damaged leaves, 7 leaves were placed
under grade 1, 5 leaves under grade 2 and 8 leaves
were placed under grade 3 (Table II). O. alta showed
damage rating of 12.38% and adjusted damage rating
of 43.54%. On the basis of damage rating, this wild
species of rice was placed under score 3 and was
moderately susceptible to leaffolder (Table III). In a
total of 53 leaves, the damaged leaves numbered 30
in O. australiensis plants, giving a high percent
infestation of 56.6. Out of the 30 damaged leaves, 6
leaves were of grade 1, 8 were of grade 2 and 16
leaves were of grade 3 (Table II). This wild species
gave damage rating and adjusted damage rating of
22.01 and 77.43%, respectively. O. australiensis
manifested damage rating score of 9 and showed high
level of susceptibility to leaffolder (Table III). O.
barthii showed percent infestation of 36.66, while the
damaged leaves numbered 11 in a total 31 leaves. In
the damaged leaves, 4 leaves were placed under grade
4, 2 under grade 2 whereas 5 leaves were placed
under grade 3 (Table II). O. barthii gave damage
rating of 12.36% and adjusted damage rating of
43.47%. On the basis of damage rating, O. barthii
came under scale 5 showing it moderately susceptible
to leaffolder (Table III). In O. brachyantha plants
only a single leaf was observed damaged in a total of
27 leaves showing percent infestation of only 3.7. On
the basis of extent of damage, this single damaged
leaf was of grade 1 (Table II). This wild species
showed damage rating of 0.62% and adjusted damage
rating of 2.18%. O. brachyantha gave damage rating
score of 1 and showed resistance to leaffolder (Table
III). Damaged leaves in O. grandiglumis plants were
20 out of 53 leaves with 37.73 percent infestation.
Out of the 20 damaged leaves, 5 leaves were placed
under grade 1, 3 leaves under grade 2 and 12 leaves
were placed under grade 3 (Table II). O.
grandiglumis attained damage rating of 14.78% and
adjusted damage rating of 51.98%. On basis of
damage rating, this wild species was placed under
score 7, showing susceptibility to leaffolder (Table
III). Percent infestation observed for wild species O.
glumaepatula was 30.20 with damaged leaves
numbering 13 in a total of 43 leaves. On the basis of
Sarhad J. Agric. Vol. 24, No.1, 2008 71
extent of damage, 4 leaves were of grade 1, 3 were of
grade 2 and remaining 6 leaves were of grade 3
(Table II). This wild species gave damage rating of
10.85% and adjusted damage rating of 38.16%. O.
glumaepatula gave damage rating score of 5 and
showed moderate level of susceptibility to leaffolder
(Table III). Out of 57 leaves in O. latifolia plants, the
damaged leaves were 19 with 33.33 percent
infestation. Of the damaged leaves, 5 leaves were
placed under each grade 1 and grade 2 and 9 leaves
were placed under grade 3 (Table II). O. latifolia
revealed damage and adjusted damage ratings of
12.28 and 43.19%, respectively. On the basis of
damage rating, this species was placed under score 5
with moderate level of susceptibility to leaffolder
(Table III). In case of O. longistaminata, the
damaged leaves numbered 16 in a total of 43 leaves
with 37.20 percent infestation. On the basis of extent
of damage, 6 leaves were of grade 1, 3 leaves were of
grade 2 and remaining 7 damaged leaves were of
grade 3 (Table II). This wild species gave damage
rating of 12.79% and adjusted damage rating of 45%.
O. longistaminata gave damage rating score of 5 and
was moderately susceptible to leaffolder (Table III).
Percent infestation observed for O. meridionalis was
20 with damaged leaves numbering 7 in a total of 35
leaves. Of the 7 damaged leaves, 2 leaves each were
recorded for grade 1 and 2 and remaining 3 leaves
were of grade 3 (Table II). O. meridionalis gave
damage and adjusted damage ratings of 7.14 and
25.12%, respectively. On the basis of damage rating
this species got a score of 3 and showed moderate
level of resistance to leaffolder (Table III). Out of 28
leaves of O. nivara plants, the damaged leaves
numbered 10, showing 35.71 percent infestation. Of
the damaged leaves, 3 were of grade 1, 2 were of
grade 2 and remaining 5 leaves were of grade 3. This
wild species showed damage rating of 13.09% and
adjusted damage ratings of 46.04%. O. nivara was
placed under scale 5 of damage rating with moderate
level of susceptibility to leaffolder (Table III). O.
officinalis gave percent infestation of 29.54. In a total
of 44 leaves of O. officinalis plants, 13 leaves were
observed damaged. On the basis of extent of damage,
4 leaves were of grade 1, 2 were of grade 2 and 7
leaves were of grade 3 (Table II). It gave damage and
adjusted damage ratings of 10.98 and 38.63%,
respectively. O. officinalis gave damage rating score
of 5 and was moderately susceptible to leaffolder
(Table III). In O. punctata plants the damaged leaves
numbered 11 in a total of 45 leaves with percent
infestation of 24.44. Of the 11 damaged leaves, 3
leaves were placed in grade 1, 2 leaves in grade 2 and
remaining 6 were placed in grade 3 (Table II). It
recorded damage rating of 9.26% and adjusted
damage ratings of 32.57%. On the basis of damage
rating, O. punctata got score 5 and showed moderate
level of susceptibility to leaffolder (Table III).
Damaged leaves in O. rhizomatis were 14 in a total of
43 leaves with 32.55 percent infestation. On the basis
of magnitude of damage, 3 leaves each were recorded
for grade 1 and grade 2 whereas 8 leaves were placed
in grade 3 (Table II). It showed damage and adjusted
damage ratings of 12.79 and 45%, respectively. O.
rhizomatis got damage rating score of 5 and was
moderately susceptible to leaffolder (Table III). In O.
rufipogon plants, the damaged leaves numbered only
2 out of a total of 38 leaves with a low percent
infestation value of 5.26. The only 2 damaged leaves
observed for this wild species were of grade 1 (Table
II). It recorded damage and adjusted damage ratings
of 0.88 and 3.09%, respectively. On basis of damage
rating, O. rufipogon gave score 1 and showed
resistance against leaffolder (Table III). Bas-385, IR-
6 and KSK-282 which are widely cultivated varieties
in Pakistan gave percent infestation values of 39.39,
33.33 and 37.5, respectively. In Bas-385 plants,
damaged leaves numbered 13 in a total of 33 leaves.
On the basis of quantum of damage, 2 leaves were
placed in grade 1, 3 leaves in grade 2 and remaining
8 leaves were placed in grade 3 (Table II). Bas-385
gave damage rating of 16.16% and adjusted damage
rating of 56.84%. It got damage rating scale of 7 and
showed susceptibility to leaffolder (Table III). In IR-
6 plants, the damaged leaves were 11 in a total of 33
leaves. Of the 11 damaged leaves observed for this
cultivated variety, 3 leaves were of grade 1, 2 were of
grade 2 and remaining 7 leaves were of grade 3
(Table II). IR-6 recorded damage and adjusted
damage ratings of 12.62 and 44.39%, respectively.
On the basis of damage rating, it attained scale 5,
showing moderate level of susceptibility to leaffolder
(Table III). In KSK-282 plants, 12 leaves were
observed damaged in a total of 32 leaves. Out of 12
damaged leaves, 3 leaves were placed in grade 1, 2 in
grade 2 and 7 were placed in grade 3 (Table II).
KSK-282 exhibited damage rating of 14.58% and
adjusted damage rating of 51.28%. It gave damage
rating score of 7 and was susceptible to leaffolder
(Table III). TN1, a susceptible check used in the
study gave a percent infestation value of 64.70. Out
of 34 leaves in plants of this susceptible check,
damaged leaves numbered 14. On the basis of
magnitude of damage, 2 leaves were of grade 1, 4
leaves were of grade 2 and 16 leaves were of grade 3
(Table II). TN1 showed damage and adjusted damage
ratings of 28.43 and 100%. TN1 was placed in scale 9
of damage rating and was found highly susceptible to
leaffolder (Table III).
The data revealed that majority of tested wild rice
species were susceptible to leaffolder. O.
Syed Mehar Ali Shah, et al. Characterization of wild rice species in response to lenffolder …… 72
australiensis was highly susceptible to leaffolder with
maximum damage rating score of 9 and highest
percent infestation of 56.6. O. alta, O. barthii, O.
grandiglumis, O. glumaepatula, O. latifolia, O.
longistaminata, O. nivara, O. officinalis, O. punctata
and O. rhizomatis gave damage rating score of 5 and
were moderately susceptible to leaffolder. All of
these wild species showed percent infestations of
above 30 except O. officinalis and O. punctata which
gave infestations of 29.54 and 24.44%, respectively.
O. meridionalis showed moderate level of resistance
with damage rating score of 3 and 20 percent
infestation. However, two wild species, O.
brachyantha and O. rufipogon were found resistant to
leaffolder with damage rating scale of 1. O.
brachyantha and O. rufipogon showed low percent
values of 3.7 and 5.26, respectively. This
manifestation of resistance of wild rice against
leaffolder is in line with findings of Gupta et al.
(2003), Mishra et al. (2002), Singh and Singh (2001)
and Patnaik et al. (2000). In all these studies, rice
germplasm was evaluated for resistance to leaffolder
and resistant sources of varying degree against this
insect pest were identified. O. brachyantha and O.
rufipogon seemed to possess resistance genes against
leaffolder. Apart from resistant genes, leaves of O.
brachyantha were comparatively narrower. This
reduced leaf area could also have played a principal
role in keeping leaffolder away from this wild
species. However, leaves of O. rufipogon were not
narrower and so in this wild species resistant genes
solely seemed to be responsible for quite low
infestation of this pest. Further studies need to be
carried out to investigate mechanism of resistance. Of
the cultivated varieties used in the present study, Bas-
385 and KSK-282 were found susceptible to
leaffolder, with damage rating score of 7 while IR-6
was moderately susceptible with damage rating score
of 5. These observations are in line with findings
Ahmed et al. (2000) and Rehman (2003). In the
reported studies, locally available rice germplasm of
the country was screened against leaffolder under
controlled conditions and none of the cultivated
variety was found resistant.
CONCLUSIONS
The resistance sources against leaffolder observed
during the present study identifies new sources of
desired resistant genes and avenues to incorporate
resistance genes from these wild relatives to
cultivated rice to develop resistance against this
insect pest. Cultivation of insect resistant rice
cultivars is a major component of IPM endeavors and
is highly compatible with other control measures. It is
also the preferred strategy by the farming community
as planting insect pest resistant cultivars help them
avoid extra cost associated with chemical sprays.
Furthermore, growing of these pest resistant
genotypes do not appear to disturb the natural
ecosystem and is environment friendly as well.
Table I: International Rice Genebank Collection (IRGC) accession number and source countries of wild rice
species tested for resistance against leaffolder at NARC, Islamabad during 2005.
Wild rice species IRGC accession Source country
O. alta 100161 Brazil
O. australiensis 103303 Australia
O. barthii 100921 India
O. brachyantha 101233 Sierra Leone
O. grandiglumis 105144 Brazil
O. glumaepatula 100184 Cuba
O. latifolia 100966 Panama
O. longistaminata 101200 Nigeria
O. meridionalis 101145 Australia
O. nivara 104644 Thailand
O. officinalis 100954 India
O. punctata 100892 India
O. rhizomatis 103410 Sri Lanka
O. rufipogon 103308 Taiwan
Sarhad J. Agric. Vol. 24, No.1, 2008 73
Table II: Reaction of wild species and cultivated varieties of rice to leaffolder under greenhouse
conditions at NARC, Islamabad during 2005.
Rice genotypes Leaves Leaves with damage grade
Total Damaged % Infestation 1 2 3
O. alta 55 20 36.36 7 5 8
O. australiensis 53 30 56.60 6 8 16
O. barthii 31 11 36.66 4 2 5
O. brachyantha 27 1 3.70 1 0 0
O. grandiglumis 53 20 37.73 5 3 12
O. glumaepatula 43 13 30.23 4 3 6
O. latifolia 57 19 33.33 5 5 9
O. longistaminata 43 16 37.20 6 3 7
O. meridionalis 35 7 20.00 2 2 3
O. nivara 28 10 35.71 3 2 5
O. officinalis 44 13 29.54 4 2 7
O. punctata 45 11 24.44 3 2 6
O. rhizomatis 43 14 32.55 3 3 8
O. rufipogon 38 2 5.26 2 0 0
Bas-385 33 13 39.39 2 3 8
IR-6 33 11 33.33 3 2 7
KSK-282 32 12 37.50 3 2 7
TN1 34 22 64.70 2 4 16
Table III: Status of wild species and cultivated varieties of rice in response to leaffolder based on % damage-rating (R),
adjusted % damage rating (D) under greenhouse conditions at NARC, Islamabad during 2005.
Rice genotypes R D Scale Status
O. alta 12.38 43.54 5 MS
O. australiensis 22.01 77.43 9 HS
O. barthii 12.36 43.47 5 MS
O. brachyantha 0.62 2.18 1 R
O. grandiglumis 14.78 51.98 7 S
O. glumaepatula 10.85 38.16 5 MS
O. latifolia 12.28 43.19 5 MS
O. longistaminata 12.79 45.00 5 MS
O. meridionalis 7.14 25.12 3 MR
O. nivara 13.09 46.04 5 MS
O. officinalis 10.98 38.63 5 MS
O. punctata 9.26 32.57 5 MS
O. rhizomatis 12.79 45.00 5 MS
O. rufipogon 0.88 3.09 1 R
Bas-385 16.16 56.84 7 S
IR-6 12.62 44.39 5 MS
KSK-282 14.58 51.28 7 S
TN1 28.43 100 9 HS
R= Resistant MR= Moderately Resistant MS = Moderately Susceptible
S = Susceptible HS= Highly Susceptible
Syed Mehar Ali Shah, et al. Characterization of wild rice species in response to lenffolder …… 74
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