GENE EXPRESSION ANALYSIS OF RICE GENOTYPES DURING RICE TUNGRO VIRUS INFECTION
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Date
2013
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ACHARYA N.G. RANGA AGRICULTURAL UNIVERSITY
Abstract
Rice tungro disease (RTD) is a major constraint in production of rice (Oryza
sativa L.) not only in India but in all South and Southeast Asia. In Andhra Pradesh, rice
tungro disease (RTD) has been reported to occur in almost all the popular rice cultivars
grown in Khammam, East Godavari, Ranga Reddy, West Godavari, Medak, Nalgonda,
Nellore, Chittoor and Prakasam districts. Host plant resistance is the most effective and
economical method for control of this virus disease. Regular research is required in
search of useful genes providing resistance against various strains of virus. Keeping this
in view, a detailed study on gene expression analysis of rice genotypes infected with
rice tungro virus was conducted at Department of Plant Pathology, College of
Agriculture, ANGRAU in collaboration with Directorate of Rice Research (DRR),
Rajendranagar, Hyderabad, Andhra Pradesh, India during the year 2012-2013.
One hundred and twenty rice genotypes (120) comprising of fifty one (51) rice
entries of International Rice Tungro Nursery (IRTN) lines and sixty six (66) rice entries
of N 22 mutants along with two resistant rice cvs. Vikramarya and Nidhi and one
susceptible check T(N)1 collected from DRR, Hyderabad, India were screened against
RTD using viruliferous GLH vector under glasshouse conditions. Among the screened
rice genotypes, twenty nine (29) rice genotypes (N22M RT 443, N22M RT 444,
N22M RT 16, N22M RT 152-2, N22M RT 418, N22M RT 360, N22M RT 407,
ASD 7 (ACC6303), IR 62, IR 72, Moddai Karuppan (ACC15471), Pankhari 203
(ACC5999), Ptb 8 (ACC6291), TKM 6 (ACC237), ARC10312 (ACC12428),
ARC12596 (ACC22176), Palasithari 601 (ACC12069), Utri Merah (ACC16680),
Utri Merah (ACC16682), Utri Rajapan (ACC16684), Balimau Putih (ACC17204),
Tjempo Kijik (ACC16602), CNTLR85033-9-3-1-1, DM24, DR31, Milagrosa
(ACC5159), ARC 11554 (ACC 21473), Nidhi and Vikramarya) showed resistant
reaction, thirty seven (37) rice genotypes showed moderately resistant reaction while
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forty seven (47) rice showed susceptible reaction and seven (7) rice genotypes showed
highly susceptible reaction against RTD.
Resistant rice genotypes produced symptoms after 21 days of inoculation with
mild or no symptoms at the time of scoring. Moderately resistant genotypes produced
11- 30% partial yellow leaf discoloration symptoms at 15-20 days after inoculation with
RTV whereas the susceptible genotypes expressed symptoms at 10-15 days after
inoculation with RTV and produced 31-50% yellow to orange leaf discoloration and
highly susceptible genotypes recorded > 50 % yellow to orange leaf discoloration.
Interveinal chlorosis and twisting of tips of leaves were observed in moderately
resistant, susceptible and highly susceptible rice genotypes.
Six rice cvs. T(N)1 and Tapaswini (susceptible), IR 20 and IR 67406-6-3-2-3
(moderately resistant), TKM-6 and Vikramarya (resistant) were tested against RTD on
yield parameters. The results showed that the resistant rice cv. Vikramarya was less
affected cultivar in terms of plant height when inoculated with RTV at 60 DAS with
0.35 % increase and 0.89 % reduction in plant height at 50 DAS. Whereas resistant rice
cv. TKM-6 when inoculated with RTV at 60 DAS showed 2.53 % reduction in plant
height. Moderately resistant rice cvs. IR 20 and IR 67406-6-3-2-3 showed less reduction
in terms of plant height as compared to susceptible rice cvs. T(N)1 and Tapaswini.
Reduction in number of panicles per plant was found less in Vikramarya inoculated
with RTV at 60 DAS (1.53 %) and 40 DAS (1.91 %). Healthy plants of rice cvs. T(N)1
and Tapaswini produced more number of panicles per plant than those of IR 20,
IR67406-6-3-2-3, TKM-6 and Vikramarya.
A significant decrease of 15.51 % in number of grains per panicle was observed in
rice cv. Vikramarya when inoculated with RTV at 20 DAS while a decrease of 16.25 %
was noticed in TKM-6 plants when inoculated with RTV at 20 DAS. However rice cvs.
TKM-6 and Vikramarya when inoculated with RTV at 60 DAS had almost no
significant effect on number of grains per panicle. In terms of grain yield per plant
Vikramarya, TKM-6 and IR 20 was less affected when inoculated with RTV at 60 DAS
with increase of 0.49 % and decrease of 3.38, 3.40 % , respectively. The most affected
cultivars in terms of hundred-grain weight was T(N)1 when inoculated at 20 DAS as
the inoculated plants did not reach the flowering phase to produce panicles while rice
cv. Vikramarya showed an increase of 0.42 and 1.25 % in hundred-grain weight when
inoculated at 50 DAS and 60 DAS. The effect of RTV infection on all quality
parameters was high when cultivars were inoculated with RTV at 20 DAS and it was
found less when inoculated at 30, 40, 50 and 60 DAS, respectively.
Gene expression studies of selected genes (PBZ1, LRR, CAT and RF2a) in
susceptible rice cv. T(N)1 and resistant rice cv. Nidhi by artificial inoculation of RTV
using viruliferous GLH revealed that PBZ1 gene was up-regulated in RTV inoculated
shoot and root of both rice cvs. T(N)1 and Nidhi. In mock inoculated root of both
cultivars PBZ1 gene was up-regulated whereas it was down-regulated in mock
inoculated shoot of T(N)1. LRR gene showed up-regulation in RTV inoculated root and
mock inoculated root of both rice cvs. T(N)1 and Nidhi whereas it showed downregulation
in RTV inoculated shoot and mock inoculated shoot of both rice cvs. T(N)1
and Nidhi. CAT gene showed up-regulation in RTV inoculated root of both rice cvs.
T(N)1 and Nidhi and down-regulation in RTV inoculated shoot of both rice cvs. T(N)1
and Nidhi. In mock inoculated shoot and root of T(N)1, CAT gene was down-regulated
whereas it was up-regulated in mock inoculated root of rice cv. Nidhi and downregulated
in mock inoculated shoot of rice cv. Nidhi. RF2a gene expression pattern in
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shoot and root of both cvs. T(N)1 and Nidhi was found similar as the expression pattern
of CAT gene.
Expression of targeted genes viz., PBZ1, LRR, CAT and RF2a was found similar
in mock inoculated leaf and shoot of both rice cvs. T(N)1 and Nidhi. Whereas, similar
gene expression was recorded with PBZ1, LRR, CAT and RF2a genes in RTV
inoculated leaf and shoot of both rice cvs. T(N)1 and Nidhi. Gene expression studies in
resistant and susceptible cultivars against RTV showed more up-regulation of selected
genes (PBZ1, LRR, CAT and RF2a) in resistant rice cv. Nidhi than in susceptible rice
cv. TN(1) indicating the possible role of genes and transcription factors in acquiring
resistance in rice during RTV infection.
Description
Keywords
rice, application methods, planting, diseases, genes, biological phenomena, vegetative propagation, viruses, genotypes, grain