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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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of lCPL 84060, ICPL 87119, ICPL 187-1, and ICPL 98001 were dn par with the resistant check, ICPL 332. In case of ICPL 98001, the 'b' value was greater than I, and residual mean square equal to zero; indicating its adaptability to high-yielding environments (Eberheart and Russell, 1966). For ICPL 84060, ICPL 87119 and ICPL 187-1; the grain yields were unstable with zero RMS values and bi I.

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compared to the long-duration genotypes. This may be because of greater H,armigera population early in the season (September to October) than during the later part of the season (November to December) when there is a slight decline in temperature. On pigeonpea, most of the eggs were laid on flowers and flower buds, and sparingly on the leaves (mostly during the vegetative phase of the host). In the field, the larval population was significantly greater on the top flowers and pods compared to the flowers and pods at middle and lower parts. Egg laying was quite high on floral parts and new pods as compared to foliage. Egg count was low on the H. armigera resistant lines such as ICPL 332, ICPL 84060, lCPL 871 19, lCPL 88039, and T 21 compared to the susceptible genotypes (ICPL 87 and ICPL 87091).

This suggested that oviposition nonpreference is one of the components of resistance to H, armigera in pigeonpea.

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compared to the other genotypes tested. Egg and larval numbers have also been found to be lower on pod borer-resistant lines ICP 11964, ICP 1903, ICPL 84060, ICPL 87088, ICPL 87089 and ICP 1691 compared to the susceptible cultivar, ICP 1691 (ICRISAT, 1991). The number of eggs laid were more on genotypes with yellow flowers compared to the genotypes with red flowers. Similar observations

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laid and larval abundance (r = 0.32) and number of eggs and pod damage % (r 0.001) Similar observations have also been made by Lateef (1985) and = Srivastava and Srivastava (1 989). A proportion of the larvae are possibly lost due to biotic and abiotic factors, and hence, it becomes difficult to obtain reliable data on larval density as a measure of genotypic resistance to this pest. Therefore, it is important to develop reliable techniques to screen for resistance to H. armigera under laboratory and field conditions using uniform level of infestation at the most susceptible stage of the crop.

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growth and survival of H,armigera reared on leaves, flowers and pods of different pigeonpea varieties. This is similar to the observations of Sison and Shanower (1994), who showed that the H. armigera larvae reared on leaves and flowers of pigeonpea had lower larval weights and longer development times than those reared on pods. Differences in the nutritional quality of different plant parts may account for the variation observed in the growth and survival of H.armigera. Bilapate el al., (1988) showed that larval survival and adult fecundity were significantly greater on chickpea as compared to that on safflower, maize, cotton and pigeonpea. According to Vijaya Kumar and Jayaraj (1982), the preferred host plants are pigeonpea field bean, chickpea, tomato, cotton, chillies, mungbean and sorghum.

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larvae H. armigera fed on developing pods of resistant varieties were significantly lower and the duration of the both the stages were longer than in larvae fed on the susceptible variety. The growth of larvae reared on flowers was faster than that on the pods.

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reared on artificial diet containing lyophilized leaf and pod powders compared to the larvae reared on leaves, flowers and pods collected from field. This may be due to availability of more nutrients in the artificial diet. Reduced larval and pupal weights and prolonged larval and pupal periods were observed in insects reared on ICPL 332, ICPL 84060, ICP 7035, ICPL 88039 and T 21 as compared to the insects reared on ICPL 87 and ICPL 87091. These results indicated that antibiosis is one of the components of resistance to H.armigera in pigeonpea.

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and pod powders compared to the standard diet. Similar observations have earlier been made by Yoshida and Shanower (2000), who indicated that the presence of growth inhibitors in the leaf and pod powder may result in reduced survival and slow growth of the larvae. Larval survival, pupal weights, pupation and adult emergence were lower on the resistant genotypes than on the susceptible ones, and the standard artificial diet. Slower larval growth, which resulted in prolonged development, may increase the probability of predation, parasitism, infection by

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Expression of resistance to H. armigera in artificial diet impregnated with leaves, flowers or pods of different pigeonpea genotypes were quite consistent. Therefore, impregnation of different plant parts consumed by the insect into the artificial diet can be used as a reliable means of evaluating pigeonpea genotypes for resistance to H. armigera. However, the results of such assays are slightly different than those observed with the intact plant parts. Therefore, efforts should be made to establish a clear cut relationship between laboratory data based on artificial diets impregnated with different plant parts and survival and development on intact plant parts and, overall expression of resistance to H.armigera under field conditions.





Trichome types and their density in pigeonpea genotypes 5.2.3

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(Peter et al., 1995). Trichomes and their exudates and/or pod surface chemicals may provide some protection against H.armigera damage (Romeis el al.. 1999b. Sharma et al., 2001, Green et ol., 2002). Plant trichomes interfere with the searching behaviour of natural enemies of insect pests (Obrycki, 1986). Abundance of Type A trichomes and their exudates on reproductive structures also effect H. ormigeru natural enemies (Romies et al., 1996, 1998). Glandular trichomes and their exudates also influence the activity and abundance of natural enemies (Sharma et a/., 2001).

Different types of trichomes were present in the pigeonpea genotypes tested. The density of each trichome type differed significantly in pods and flowers. Genotypic differences and environmental factors affect the growth and development of trichomes (Southwood, 1986).

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in flowers and pods of the pigeonpea genotypes examined. In case of pods, Type 'D' trichomes were present in greater numbers compared to Type A trichomes.

Trichomes were present in greater density towards the edges than in the middle areas of flowers and pods. Similar observations have been made by Romeis et al. (1996).

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and calyxes (Romeis, 1997). High density of nonglandular trichomes (Type A and Type B) might contribute to the larval mortality in the resistant genotypes lCPL 84060, ICPL 871 19, ICPL 88039, ICPL 7203-1, ICPL 187-1 and T 21 although the cause and effect relationships needs to be established clearly.

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Sheldrake (1981) suggested that this is the source of characteristic fragrance. The secretions in the Type B-trichome are liberated only when the cell wall is ruptured.

This could be caused by a chewing insect such as H.armigera or by abiotic factors such as high temperatures or low air humidity (Ascensao et al., 1995). Bisen and Sheldrake (1981) considered Type E trichome to be a developmental stage of type B. Since no intermediate forms between Type E add Type B are found, Type E is considered to be a separate trichome type.

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and were present in all the 12 genotypes examined. Type E trichomes were low or absent in a few genotypes. On the pods, Type D trichomes were greater in ICPL 187-1 than in ICP 7035.

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Nutritionally important constituents of a host plant play a significant role in the feeding behaviour of phytophagous insects (Beck and Hanec, 1958). The phosphorus and potassium contents in flowers and pods of the pigeonpea genotypes differed significantly. The levels of potassium and phosphorus were lower in pod borer resistant genotypes such as ICPL 332, lCPL 84060, ICPL 7035 and ICPL 187-1, but high in case of susceptible genotype, ICPL 87. Highest potassium content was observed in ICPL 87091 (susceptible genotype). Lowest potassium content was observed in ICPL 88039, which is a short-duration type and is relatively less susceptible to pod borer damage. Protein content was highest in ICPL 332, ICPL 7035, and ICPL 84060. ICPL 332, ICPL 84060, ICPL 7035, and ICPL 871 19 which are long-duration types and hence tolerance or recovery to pod borer damage is one of the components of resistance. Because of high protein content, the damage by H. armigera may be more. Similar observations have been made by Khurana and Verma (1983). Highest sugar content was recorded in leaves and pods of ICPL 187-1 and lowest in ICP 7035 leaves and pods of T 21.

Bioassay of pod surface extracts from ICPL 87 (susceptible 5.2.5

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ICPL 332 suggested that the compounds on the pod surface play an important role in feeding preference by larvae of H. armigera. The feeding indices and antifeedant activity confirmed that the compounds extracted from pod surface of ICPL 87 by

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upon pods. Specially, switching From feeding primarily on flowers (up to the 3d instars) to feeding upon both flowers and pods (4' and 5" instars) may be due to differences in nutritional requirements for different instars. Older larvae have increased appetite (Raubenheimer and Barton, 2000) and need more proteins (Simpson et al., (1988), and this may be one of the factors responsible for a change in feeding behaviour of different larval instars.

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pigeonpea genotypes tested, there was high damage in flowers and pods of the susceptible genotypes such as ICPL 87 and ICPL 87091. These observations were similar to genotypic reaction under field conditions. In case of ICPL 84060, ICPL 332, ICP 871 19, ICP 7035, ICPL 88039, and ICPL 187-1, lower pod damage was observed both under field and laboratory conditions. This indicates that the larvae are able to select the nutritionally more optimum food when a choice is offered between a resistant and a susceptible genotype.

Differences in pod surface chemistry, that resulted from extraction of pod surface compounds in different solvents affected the behaviour of H. armigera larvae. In case of resistant genotypes such as ICPL 84060, ICPL 88039, ICP 7203-1 and ICPL 98008, more damage was observed in pods extracted in hexane than in the control pods. The results of these studies suggested that the compounds on the pod surface of pigeonpea genotypes play an important role in acceptance or rejection of food by H. armigera larvae.

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stage was very low. However, during the reproductive stage, the larvae damaged the flowers and developing pods. There was a significant and positive correlation between the larval population and pod damage (r = 0.585).

Pigeonpea genotypes with indeterminate growth habit were less susceptible than the genotypes with determinate growth habit. Greater infestation on the determinate plant types may be because of the fact that such genotypes have clustered flower arrangement, which might facilitate easy access to flowerdpods to the borer larvae, e.g., in ICPL 87 and ICPL 87091. These observations were similar to the findings of Kushawaha and Malik (1 988).

Significantly higher grain yield was recorded in ICPL 187- 1, ICPL 332, lCPL 84060, ICPL 7203-1, ICPL 87119, lCPL 98001, T 21 and ICPL 88039 under protected conditions as compared tp ICPL 87. Under unprotected conditions, high grain yield was recorded only in case of ICPL 84060 and ICPL 187-1.

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under protected conditions. The pod damage in lCPL 87 and ICPL 87091 was high under both protected and unprotected conditions. Both of these genotypes were of determinate type, and short- duration varieties, Indeterminate growth habit coupled with long-duration resulted in less H.armigera damage.

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par with that of the resistant check, ICPL 332, lCPL 98008, T 21 and ICPL 871 19 were on par with each other. Under protected conditions, all the genotypes were on par with the resistant check, ICPL 332 in terms of pod borer damage. Under unprotected conditions, lCPL 7035 (24.4%) was on par with the resistant check, ICPL 332 (22.9%) for pod damage. These observations suggested the presence of tolerance mechanism of resistance in pigeonpea to H. armigera damage. Loss in grain weight was lowest in ICPL 332, followed by ICPL 84060, ICPL 187-1, ICPL 87091, ICPL 871 19, ICPL 88039, ICPL 98001, and T 21.

Chapter V I

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Helicoverpa urrnigera (Hubner) in pigeonpea [Cbjanus cajan (L.) Millsp.]" was conducted at lCRISAT Patanchem during 2000-2002. The results are summarized

as follows:

1. There was a strong genotype x environment interaction for H.armigera damage and most of the genotypes were unstable across environments in terms of grain yield, except lCPL 332 (resistant check).

2. Among the genotypes tested, high grain yields were recorded in ICPL 84060, ICPL 871 19, lCPL 332, ICPL 98008 and ICPL 187-1.

3. Lowest pod damage was recorded in ICPL 187-1 (39%), followed by resistant check ICPL 332, ICPL 84060 and ICPL 88039 (47-53%, pod damage).

4. All the genotypes were unstable in their reaction to H armigera in terms of percentage pod damage. However the regression coefficient was less than unity in case of ICPL 187-1, ICP 7203-1, ICPL 88039, ICPL 98008, T 21 and ICPL 332, while ICPL 87091, ICPL 871 19 and ICPL 87 had regression coefficients greater than unity and these genotypes suffered greater pod damage with increase in the intensity of H. armigera infestation.

5. Studies on oviposition preference under no-choice, dual-choice and multi-choice conditions revealed that among medium and long duration genotypes; ICPL 332 (resistant check). Among the short-duration genotypes; the susceptible check ICPL 87 was preferred most, followed by lCPL 87091, ICP 7203-1, ICPL 88039 and ICPL 98001.



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