Mechanism of resistance to Helicoverpa armigera (Lepidoptera: Noctuidae) in chickpea: role of oxalic acid in leaf exudate as an antibiotic factor
1995
Yoshida, M. | Cowgill, S.E. | Wightman, J.A.
Mechanisms of resistance to Helicoverpa armigera Hubner in chickpea, Cicer arietinum L., were investigated. Inhibition of larval growth occurred in a feeding test using the leaves of chickpea genotypes, which had previously been identified as having resistance to H. armigera. A feeding test using unwashed and washed leaves revealed that the substance responsible for the growth inhibition was water soluble and present on the surface of the leaves. Acid components of the leaf exudate were analyzed by high-performance liquid chromatography. Oxalic acid and malic acid were detected as major components in all 4 genotypes that were analyzed. Genotypes resistant to H. armigera accumulated more oxalic acid on the leaves than susceptible genotypes. Oxalic acid showed significant 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. Inhibition of larval growth by oxalic acid was not caused by antifeedant effects but was more likely attributable to antibiosis. Malic acid had no effect on larval growth.
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