274 V. K. Lingaraj et al.
Venkataswamy 1966 ; Roy et al. 1971 ). Subse-
quent studies did not confirm this view (Shastry
et al. 1972 ; Rao 1972 ; Kalode 1973 ). Antixenosis
studies have indicated greater attraction of adult
midges toward the susceptible genotypes than the
resistant genotypes (Kalode et al. 1977 ). In this
study, significant differences were recorded on
the number of adults settled 6 h after adult re-
lease further, Kalode et al. ( 1983 ) also observed
the similar results. But this study is contradicted
by the reports of Sain and Kalode ( 1994 ) who
observed nonsignificant differences with respect
to the number of adults settled between resis-
tant and susceptible cultivars. Studies in India
(AICRIP 1969 ), Sri Lanka (Modder and Alagoda
1971 ), and Thailand (Hidaka et al. 1974 ) indicat-
ed ovipositional antixenosis by the adult female
gall midge. Kalode ( 1980 ) and Sain and Kalode
( 1994 ) also found significant differences in the
number of eggs laid on resistant and susceptible
rice varieties. This study also revealed significant
differences in the number of eggs oviposited on
the resistant and susceptible cultivars.
Nevertheless, these differences could not be
linked to resistance against gall midge. In view
of the short adult life span of one day and total
inactivity of adults during the day time, it is not
surprising if antixenosis component is not clearly
expressed in rice gall midge. In this study, NDR
2063, JGL 11459, and JGL 13376 despite record-
ing comparable proportion of eggs to the suscep-
tible TN1 and Jaya, continued to be resistant.
Antibiosis
Among the genotypes, maximum number of live
maggots after 7 days of release was observed on
TN 1 (5.77 per plant) and Jaya (4.22 per plant),
and was significantly superior compared to the
rest. The number of live maggots at 7 days after
release on OR 2093-4, RDR 987, OR 1914-8,
NDR 3110, NDR 2063, MTU 1075, RP 4644-
1183, RP 4613-260, RP 4647-1073, and JGL
13595 was 1.11, 1.22, 1.33, 1.44, 1.55, 1.88,
2.10, 2.66, 3.44, and 3.44 maggots per plant, re-
spectively. But, the maggots in all the resistant
genotypes tested remained in the first instar while
in susceptible genotypes the maggots reached the
second instar. At 14th day after adult release, in
all the resistant genotypes the mortality of mag-
gots was evident but in JGL 13595 and RP 4647-
1073, live maggots were observed. But still the
maggots remained in the first instar only, while
in susceptible genotypes they moulted to second
and third instars (Table 1 ).
Observations on 18th day revealed high mag-
got mortality in all the resistant donors includ-
ing JGL 13595 and RP 4647-1073, while most of
the surviving insects on TN 1 and Jaya were in
pupal stage. Not only survivals of maggots were
adversely affected on resistant varieties, even the
development of surviving insects was retarded.
In 2006 wet, 7 days after adult release, signifi-
cantly higher numbers of live maggots ( P < 0.05)
were noticed in TN 1 and Jaya which recorded
6.33 and 5.33 maggots/plant and were on par
with each other. Among the resistant genotypes,
lower (0.77 maggot per plant) number of mag-
gots was observed in WGL 157 and significantly
differed other genotypes. Likewise, the number
of live maggots on OR 1967-15, JGL 13418,
JGL 11459, RP 4643-713, and JGL 11605 was
0.88, 1.33, 1.66, 1.99, and 2.33 maggots/plant,
respectively. Though the maggot survival was
noticed on resistant genotypes at 7 days of adult
release, the maggots remained in the first instar
only, while in the susceptible genotypes, TN 1
and Jaya, the maggots reached the second instars
(Table 2 ).
After 14 days of adult release, on resistant
genotypes maggot mortality was observed ex-
cept in JGL 13376 and NDR 9930095, where
the maggots remained in first instar only. But,
on susceptible genotypes, TN 1 and Jaya sec-
ond- and third-instar maggots were observed.
Further, subsequent observations on 18th day of
adult release indicated higher maggot mortality
on the resistant genotypes including JGL 13376
and NDR 9930095. Most of the surviving mag-
gots in TN 1 and Jaya were already in pupal stage
on 18th day. Thus, antibiosis is evident; not only
in survival of maggots were adversely affected
on resistant genotypes, but even the development
of surviving maggots was retarded.
So, in the present investigation distinct anti-
biosis effects leading to mortality of maggots on
the resistant cultivars were evident. This study