Impact of Gall Midge, Orseolia Oryzae (Wood-Mason) Infestation on Total ... 265
2.96 and 3.92 μg/g, respectively, and it increased
to 6.19, 5.26 and 6.86 μg/g, respectively, on the
fifth day and 11.96, 10.21 and 13.50 μg/g on the
seventh day after infestation, respectively. Thus,
the rapid accumulation of proline in relation to
insect infestation in susceptible genotypes indi-
cated clearly their role under stress conditions.
Among the genotypes, studies for proline
profile in relation to gall midge infestation were
significantly higher with rapid accumulation of
proline on the third, fifth and seventh day after
infestation in susceptible genotypes. In resistant
genotypes this phenomenon was not evident. On
the third day after infestation, the proline con-
tent in susceptible genotypes viz., Jaya, IR20
and TN1 was 3.70, 2.96 and 3.92 μg/g and it in-
creased to 6.19, 5.26 and 6.86 μg/g on the fifth
and 11.96, 10.21 and 13.50 μg/g on the seventh
day after infestation, respectively.
Thus, the rapid accumulation of proline in
relation to insect infestation in susceptible geno-
types indicated clearly their role under stress con-
ditions. Silver shoots caused by gall midge infes-
tation contained higher levels of proline than the
healthy leaves. Even the healthy leaves from the
damaged plant contained more amount of proline
than the healthy leaves of the noninfested plant
as reported by Roy et al. ( 1988 ). In the present
study also higher accumulation of proline in sus-
ceptible (infested) genotypes was evident.
These observations clearly showed that insect
damage stimulates increase in free proline level
in rice and the concentration increases in the in-
sect damaged plants compared to the noninfested
plants (resistant). A similar trend of proline ac-
cumulation was reported in brown plant hopper
infestation, where the stems of the affected plants
(hopper burnt hills) possessed higher concen-
tration of proline than the stems of noninfested
plants (Roy et al. 1988 ). Thus, in physiological
stress, biotic stress caused by diseases (Mohanty
and Sridhar 1982 ) in the present study also makes
it evident that the gall midge infestation also in-
duces accumulation of free proline in rice plants.Indole Acetic Acid (IAA)
The data on IAA profile in resistant and suscep-
tible genotypes in relation to gall midge infesta-
tion are presented in Fig. 3. On the day of infesta-
tion, significant differences among the genotypes
were observed. Further, the day of infestation
had significant effect on the IAA. Among the
test genotypes, significantly higher accumulation
of IAA on the third, fifth and seventh day after
infestation was noticed in the infested suscep- ,$$ JJ-*/ 53 5'5 $EKD\D
-D\D 6 ,5 6 71 6 71 8QLQIHV WHG Fig. 3 Effect of gall midge infestation on indole acetic acid (days after infestation)