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Accueil du site → Doctorat → Inde → Mechanisms of Resistance to Helicoverpa armigera (Hubner) in pigeonpea [Cajanus cajan (L.) Millsp.]

Acharya N G Ranga Agricultural Univerisity (2005)

Mechanisms of Resistance to Helicoverpa armigera (Hubner) in pigeonpea [Cajanus cajan (L.) Millsp.]

Anita Kumari, D

Titre : Mechanisms of Resistance to Helicoverpa armigera (Hubner) in pigeonpea [Cajanus cajan (L.) Millsp.]

Auteur : Anita Kumari, D

Etablissement de soutenance : Acharya N G Ranga Agricultural Univerisity

Grade : PhD thesis 2005

The present investigations on "MECHANISMS OF RESISTANCE TO Helicoverpa armigera (Hubner) IN PIGEONPEA [Cajanus cajan (L.) Millsp.]" were undertaken under laboratory and field conditions at International Crops Research Institute For Semi Arid Tropics (ICRISAT), Patanchem, Andhra Pradesh, India during 2000 - 2001 and 2001-2002 cropping seasons. Twelve germplasm accessions of pigeonpea were evaluated for stability of resistance to H. arrnigera under natural infestation. Stability of resistance was measured by regression analysis of the data for pod damage and grain yield. Amongst the 12 genotypes tested, lowest pod damage was recorded in ICPL 187-1 (39%) followed by ICPL 332, ICPL 84060, and ICPL 88039 (47-53%). For ICPL 84060, the regression (b) value was and residual mean square equal to zero. However the pod damage percentage was not stable over the seasons. Mechanisms of resistance (antixenosis for oviposition, antibiosis and tolerance) to H. armigera in 12 pigeonpea genotypes were studied in laboratory and field conditions. Oviposition studies under no-choice, dual-choice and multi-choice conditions revealed that among the medium to long duration genotypes ICPL 871 19 and ICP 7035 were preferred for oviposition compared with ICPL 84060 and ICPL 332 (resistance check). Among the short-duration genotypes, the susceptible check ICPL 87 was preferred most, followed by ICPL 87091, ICP 7203-1, lCPL 88039, and ICPL 98001. Reduced larval and pupal weights, and prolonged larval and pupal development was recorded on artificial diet impregnated with lyophilised leaves and pods of ICPL 332, ICPL 84060, ICP 7035, ICPL 187-1, ICPL 88039 and ICP 7203-1 as compared to the susceptible genotypes ICPL 87 and ICPL 87091 indicating the presence of antibiosis component of resistance to H, armigera in these genotypes. Five morphologically distinct trichomes : Type A, B, C, D and E were identified on pods and calyxes of the 12 pigeonpea genotypes studied. Type A and B trichomes were present in greater density in flowers and pods. In case of pods, Type D trichomes were present in greater numbers compared to Type A. High density of nonglandular trichomes (Type A and Type B) might contribute to the larval mortality in the resistant genotypes (ICPL 84060, ICPL 871 19, ICPL 88039, ICP 7203-1, ICPL 187-1 and T 21). The pod surface extracts of ICPL 87 and lCPL 332 stimulated feeding by the third, fourth and fifth instar larvae of H. armigera when presented at pod surface equivalents. The attractions of H. armigera larvae to ICPL 87 and ICPL 332 plant extracts appears to result from chemical compounds present in the extracts. Nutritionally inlportant constituents of a host plant play a significant role in the feeding behaviour of phytophagous insects. The levels of Potassium and Phosphorus were low in resistant genotypes such as ICPL 332, ICPL 84060, ICP 7035 and JCPL 187-1, but high in susceptible check lCPL 87. Higher protein content was observed in resistant geneotypes ICPL 332, ICP 7035 and ICPL 84060 as compared to susceptible check lCPL 87. The loss in grain yield due to H. armigera in 12 pigeonpea genotypes under protected and unprotected field conditions indicated the presence of tolerance mechanism of resistance in pigeonpea genotypes. Reduction in grain yield was lowest in the resistant check ICPL 332, followed by ICPL 84060, ICPL 87 and lCPL 87 1 19 indicating tolerance to pod borer damage in these genotypes.

Présentation : ICRISAT

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