Impact of Gall Midge, Orseolia Oryzae (Wood-Mason) Infestation on Total ... 263
Total Phenols, Proline and IAA Profile
Four resistant viz., JGL 13595, RP 4639-233,
RDR 987, Abhaya and three highly susceptible
viz., Jaya, IR 20 and TN1 rice genotypes were
selected based on the field and laboratory evalu-
ation against local gall midge populations from
wet and winter seasons of 2005 and 2006. The
genotypes were grown in plastic trays as a row
of 25–30 seedlings and exposed to gall midge
populations (50 females and 10 males) 8 to 10
days after sowing. The next day the trays were
shifted to shallow trays containing water, and
plants were frequently (once in 2 h) sprayed with
water using hand atomizer to create high rela-
tive humidity for egg incubation and hatching.
Eggs hatched on the third day were treated as day
0 of infestation. Stem bases, 3–5 cm in length,
were cut from five seedlings/replication; pooled
and fresh weights were recorded before phenol
extraction in methanol at 60 °C for 20 min. Five
replications variety were maintained. The plants
were sampled on 0, 1, 3, 5 and 7 days after infes-
tation. The total phenols was estimated following
the Folin–Ciocalteau method (Bray and Thorpe
1954 ), proline by the acid ninhydrin method
(Sadasivam and Manickam 1996 ) and IAA by
the fluorimetric method of Knegt and Bruinsma
( 1973 ). The biochemical profiles in gall midge
resistant and susceptible genotypes were com-
pared with a noninfested, susceptible TN1. The
data on biochemical contents were subjected to
analysis of variance (ANOVA) and means were
separated by LSD at P < 0.001 (SPSS Inc 1999 ;
SAS 2007 ).
Results and Discussion
Total Phenols
On the day of infestation each resistant and sus-
ceptible genotypes differed significantly with
respect to total phenols. Further, the day of in-
festation had a significant effect on the total phe-
nol content in all the genotypes. All the resistant
genotypes showed increased level of phenols
from 3−7 days after infestation compared to a
susceptible and noninfested TN 1.
On the third day subsequent to infestation
all the resistant genotypes viz., JGL 13595, RP
4639-233 RDR 987, OR 1941-8, NDR 2063, JGL
11605 and Abhaya recorded significantly higher
total phenols compared to a susceptible and non-
infested TN 1. Similarly, on the fifth and seventh
day after infestation, in all the resistant genotypes
there was a rapid increase in accumulation of
total phenols compared to susceptible genotypes
viz., Jaya, IR 20 and TN 1 and the day effect on
the level of phenol contents in resistant geno-
types was found significant. The total phenol
content in resistant genotypes viz., JGL 13595,
RP 4639-233, RDR 987, OR 1941-8, NDR 2063,
JGL 11605 and Abhaya on the seventh day after
infestation was 0.576, 0.550, 0.547, 0.510, 0.520,
0.549 and 0.596 mg/g, respectively, as against
the day of infestation (0.240, 0.242, 0.290, 0.216,
0.180, 0.230 and 0.242 mg/g, respectively) in
Fig. 1.
Thus, there was a higher accumulation of total
phenols in resistant genotypes compared to sus-
ceptible genotype in relation to gall midge infes-
tation. Thus, the rapid accumulation of total phe-
nols in all the resistant genotypes following gall
midge infestation highlights the inducible bio-
chemical pathways, probably involving synthesis
of phenolic precursors and their further oxidation
into toxic quinones in the insect.
The present investigation was in close agree-
ment with the study made by Amudhan et al.
( 1999 ). Similarly, higher concentration of poly-
phenols has been reported in shoot apices of
resistant rice cultivars such as Shakti, Leauang
152 (Vidyachandra et al. 1981 ), Ptb 18 (Raja-
mani 1982 ), IET 7009, IET 7008 and Siam 29
(Joshi and Venugopal 1984 ). Increased phenolic
content in the growing point of resistant rice cul-
tivars during early infestation by gall midge has
been reported (IRRI 1977 ). In the present inves-
tigation, the amount of total phenols in relation
to gall midge infestation could be related to re-
sistance. Even in susceptible genotypes such as
Jaya, IR 20 and TN1 in the present investigation,
slight increase in phenol content was observed,
and it may be associated with the gall midge initi-