MECHANISM OF RESISTANCE TO HELICOVERPA-ARMIGERA (LEPIDOPTERA, NOCTUIDAE) IN CHICKPEA - ROLE OF OXALIC-ACID IN LEAF EXUDATE AS AN ANTIBIOTICFACTOR

Mechanisms of resistance to Helicoverpa armigera Hubner in chickpea, C icer arietinum L., were investigated. Inhibition of larval growth occu rred in a feeding test using the leaves of chickpea genotypes, which h ad previously been identified as having resistance to H, armigera. A f eeding test using unwashed and washed leaves revealed that the substan ce responsible for the growth inhibition was water soluble and present on the surface of the leaves. Acid components of the leaf exudate wer e analyzed by high-performance liquid chromatography. Oxalic acid and malic acid were detected as major components in all 4 genotypes that w ere analyzed. Genotypes resistant to H. armigera accumulated more oxal ic acid on the leaves than susceptible genotypes. Oxalic acid showed s ignificant growth inhibition on H. armigera larvae when included in a semi-artificial diet. The accumulation of oxalic acid is considered to be one of the mechanisms of H. armigera resistance in chickpea. Inhib ition of larval growth by oxalic acid was not caused by antifeedant ef fects but was more likely attributable to antibiosis. Malic acid had n o effect on larval growth.