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«D. ANITHA KUMARI THESIS SUBMITTED TO THE ACHARYA N.G RANGA AGRICULTURAL UNIVERSITY COLLEGE OF AGRICULTURE, RAJENDRANAGAR IN PARTIAI FULFILLMENT OF ...»

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Dodia et al. (1996). Growth and development of H. armigera were adversely affected on flowers of all wild species. The larval mortality during first 7 days was higher for the larvae fed on wild relatives than on pigeonpea. Very few larvae survived to the pupal or adult stages, when reared on flowers of wild species as compared to cultivated pigeonpea. Growth index and fecundity were also adversely affected in the larvae reared on wild species and their FI.The adults emerging from larvae reared on wild species were smaller than the adults which emerged from cultivated pigeonpea.

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parts on growth and survival of H,armigera. Larvae were reared on flowers, pods and leaves of six short-duration pigeonpea genotypes (ICPL 86005, ICPL 86015, ICPL 86012, ICPL 87101 ICPL 88023 and ICPL 87) under laboratory conditions.

Larval and pupal weights were significantly higher, larval developmental period significantly shorter, and adult life span significantly longer when reared on pods compared with flowers and leaves. Larvae reared on ICPL 87 had the shortest larval developmental time, the highest larval and pupal weights, and the longest adult life span. Lowest larval weights were recorded in ICPL 86012 and ICPL 86015. There was a significant variation in growth, development, and survival of H.armigera due to differences in biochemical constituents (nutrients or secondary metabolites) between genotypes and plant parts.

Srivastava and Srivastava (1990) studied antibiosis in chickpea genotypes to H. armigera (ICCX 730041, ICC 10613, ICC 10817, ICCL 79048, C 235, K 850, ICC 1403, ICC 3137). The percentage larval survival was lowest (76.8%) on ICCL - 79048, with longest larval period of 24 days and thus exhibited high level of antibiosis.

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Trichomes are a potentially important resistant mechanism, and have been utilized in developing resistant cultivars of several other crops. Previous work has indicated that for many herbivorous insects such as leafhoppers and Lepidoptera, glandular trichomes provide a resistance mechanism owing to both the compounds exuded by them (Ranger and Hower, 2001; Frelichowski and Juvik. 2001) and their density (Valverde er al., 2001; Gurr and McGrath, 2001).

Non-glandular trichomes and yellow glandular sacs are present on pods and leaves of all Cajanus species. Glandular trichomes that release chemicals are confined to the pods of C. cajan and C, platycarpus and are absent on the pods of C. scarabaeoides C. platycarpus pods have the longest non glandular trichomes.

Pods of C. scarabaeoides are highly pubescent, followed by those of C.cajan and C, platycarpus. H. armigera avoids the highly pubescent C. scarabaeoides for oviposition. Trichome density exhibited a negative impact on larval survival, growth and development. Behavioural study indicated that the neonate larvae were unable to reach the feeding site in time, which led to larval desiccation (John peter, 1995).

Differences in physical and biochemical characters between pigeonpea and its wild relatives may account for the relative differences in food preference by the larvae of H,armigera. Five types of trichomes have been identified on pods of Cajanus spp.

three glandular and two nonglandular. Pods of C. scarabaeoides have a dense covering of short non-glandular trichomes and lack the long, tubular glandular trichome common on pigeonpea and C, platycarpus pods. Pigeonpea and C. platycmpus pods are much less densely covered with non glandular trichomes than C.scarabacoides. The very dense non-glandular trichomes on pods of C. scarabaeoides provide a physical barrier to young H. armigera larvae, while the glandular trichomes secrete chemicals that act as attractants to adult moths (Hartlieb and Rembold, 1996), and also act as phagostimulants / antifeedants to the larvae of H. amigera (Sharma el al., 2001).

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The non glandular trichomes acted as physical resistance mechanism and prevented small larvae from reaching the pod surface to feed. But these trichomes were less effective for larger larvae which were able to establish and feed, but grew more slowly and took longer to develop than the larvae on the other two Cajanus spp. The

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larval growth and increased larval development period, resulting in lower pupal weight and low fecundity of H.armigera on this species ( Shanower el al., 1997).

Biochemical mechanisms of resistance 2.2.4 Nutritionally important constituents of a host plant play a significant role in the feeding behaviour of phytophagous insects (Thorstkeinson, 1960). At physiological concentrations, sugar, amino acids, lipids, salts and some secondary plant substances act as phagostimulants. A combination of these components quite often produces synergistic effects (Beck and Hanec, 1958; Thorsteinson and Nayar, 1963; Gothilfs and Beck, 1967; Doss el a!.,1982; Doss, 1983).

In addition to being phagostimulants, sterols are important for insect growth and development, lnsects are incapable of de novo synthesis of the steroid skeleton, which they requlre to synthesize the moulting hamone, ecdysone. To meet the sterol requirements, the phytophagous insects depend on their host plant or symbionts (Shanna, 1993). Ethyl acetate fraction showed phagostimulant properties compared to sucrose. Sterols (5 mgtdisc) and soybean leaf extract (40 mgldisc) in combination with (400 mgldisc) showed synergistic effect as phygostimulants.





Annadurai et al.. (1990) suggested that the relative concentrations of various phenols play an important role in determining the suitability of pigeonpea plant tissues for the presence of phloroglucinol in pods which stimulates the growth and enhances the survival of larvae. The compound resorcinol may be the cause of poor larval growth and survival on leaves.

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groups (early, medium, and late) were analyzed at green pod stage and at maturity for various biochemical parameters (proteins, total sugars, phosphorus and potassium). Total sugars on the pods varied at the two stages of pod development, and indicated that the early maturing varieties (WAS 120, ICPL 87 and TAT 10) which were susceptible to pod borer damage, had significantly higher total sugar content (3.56 to 4.70%) than the late maturing cultivars viz., PT 35, PT 25, C 11, N 290-21 (2.99 to 3.30% sugar content). Total sugar content showed a significant and positive correlation coefficient with pod borer damage (Knap el al., 1966; Singh and Jotwani, 1980, Khurana and Venna, 1983). Resistant varieties of pigeonpea have lower phosphorus and potassium contents than susceptible ones The polyphenols have been reported by several workers in different crops (Hahn et al., 1981; Khurana and Verma, 1983; Mohan el al., 1987).

Poly phenoloxidase activity in the pods of 12 cultivars of pigeonpea at two stages of growth indicated that the late-maturing cultivars (resistant to pod borer damage) had comparatively much higher activity, followed by mediummaturity cultivars (Murkute et al., 1993). Surface chemicals from pods of pigeonpea and two wild Cajanus species also effect the behaviour of H. armigera larvae. A filter paper feeding test showed that acetone extract from the surface of pigeonpea and C.platycarpus pods contains H.armigera feeding stimulants (Shanower el al.,

1997) but not in extracts from pods of C,scarabaeoides. Feeding stimulants are contained in the trichome exudates. Polar chemicals on the plant surface also stimulate oviposition behaviour of H.armigera (Romeis el at., 1999a).

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caffeoylquinic acids was evaluated by Kimmins el al., (1995). A mixture of compounds containing 5-caffeoylquinic acid (SCQA), 3-caffeoylquinic acid (3CQA) and a novel compound, I-caffeoyl-4 deoxyquinic acid (IcdQA), which were extracted from the wild groundnut species Arachis paraguariensis, showed inhibitory effects of larval development of H.armigera.

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stimulant for fifth instar H. armigera has shown to contain four main phenolic compounds. The four compounds were identified as isoquercetin, quercetin,

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compounds. An absence of quercetn and higher concentrations of iso-quercetene than the cultivated variety characterised pod surface extracts of pod borer resistant cultivars. In addition, the ratio of stilbene to quercetene 3 methyl ether was greater in the pod borer resistant cultivars (Green et al., 2003).

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Tolerance provides the plant an ability to produce satisfactory yield in the presence of a pest population that would result in a significant damage in the susceptible plants. Tolerant cultivars do not suppress pest populations, and thus do not exert a selection pressure on the pest population. Effects of tolerance are cumulative as a result of interacting plant growth responses such as plant vigor, inter and intra plant growth compensation, mechanical strength of tissues and organs, and nutrient and growth regulation and partitions. Plants with tolerance mechanisms of resistance have a great value in pest management as such plants prevent the evolution of new insect biotypes, and also help in maintaining the populations of the natural enemies. Development of new insect biotypes capable of feeding on resistant cultivars with antixenotic or antibiosis mechanisms of resistance can be delayed or minimized by utilizing tolerance as a polygenic resistance (Tingey, 1981).

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Nos. 94, 154, 151, 289, 184, 146, 83 17, 8322, 315, 267, and 148) for resistance to H. armigera, which were of early-maturity group and determinate type of growth habit. The mean pod damage over three years indicated that ICPL 154 and ICPL 94 recorded low levels of pod damage of 9.8 and 10.9%, respectively, as compared to the other test cultivars.

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H.amigera was determined in field plot tests in Rahuri in1978. None of larvae of the entries were free from infestation, but those least susceptible were nos.148 Hy-2,

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International Crops Research Institute for Semi Arid Tropics, Patancheru, between June 2000 to December 2002. The materials and methods used in conducting these experiments are elucidated below.

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The present investigation was conducted at ICRISAT (International Crops Research Institute for the Semi-Arid Tropics), Patancheru, India. The latitude and longitude are 17" 27W and 78" 28'E, respectively, and altitude is 545 m above sea level. Four plantings were taken up in two years between 2000-2002.

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earlier developed at ICRISAT are given below.

Short duration genotypes: ICPL 87,ICPL 98001,ICPL 98008,ICPL 87091,ICPL 88039,T 21, ICPL 187-1,ICP 7203-1.Among these ICPL 87 and ICPL 98001 are determinate types while the other genotypes have a indeterminate type of growth habit. Plant growth habit has a substantial influences on the extent of pod borer

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There were 36 plots (each plot having 4 rows, 4 m long during kharif2000-01 and 6 rows, 4 m long during khurif2002). There were three replications in a randomized complete block design. To reduce the incidence of seed born diseases, the seeds were treated with thiram ( j g kg") of seed. The treated seed were sown on 22ndJune and 21" July 2000. During kharif2001-02 the crop was sown on 26* June and 28* July 2001. The rows were spaced at 75 cms, and the spacing between the plants within a row was 30 cm. The plots were separated by an alley of 1 m. The seeds were sown with a 4-cone planter at a depth of 5 cm below the soil surface at optimum soil moisture conditions. The crop was thinned to a spacing of 30 cm at

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in rows before sowing. Top dressing with urea @ 80 kg ha" was given at one month after crop emergence. Interculture of weeding was carried out as and when needed. Insecticide was applied to the untreated plot during the reproductive stage of the crop.

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recorded at maturity in pods harvested from the tagged inflorescences from random three plants. Pod borer damage to pods was quantified by expressing the number of pod borer damaged pods as a percentage of total number of pods.

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release. The significance of differences between the genotypes was determined by F-test, while the treatment means were separated by least significant difference (LSD)at P.50.05. For the twelve pigeonpea genotypes, stability analysis was done for 4 seasons by the method of Eberhart and Russel (1966) and stability statistics were analysed.

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maintained at ICRJSAT-Patancheru, India. The lab culture was regularly supplemented with field collected larvae. The larvae were reared on the chickpea based diet (Annes et a/., 1992) at 27°C (Table 2). The adults were released in a cage with nappy liners for oviposition. The adults were supplied with 10% sucrose on absorbant cotton inside the cage. Eggs laid on the liners were sterilized with 1% sodium hypochloride, and transferred into the cups for rearing on the artificial diet.

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were studied for the 12 genotypes under laboratory conditions. Among them; ICPL 87 and ICPL 332 were used as susceptible and resistant checks, respectively.

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12 hours). The twigs /inflorescences used for studying antixenosis were procured from the field. The plant material was thoroughly examined for the presence of eggs or larvae before use in laboratory.

Table 2: Chemical composition of diet used for rearing H.ormigera larvae (Armes et al., 1992)

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