Tolerance to Simulated Pod‐Borer Herbivory Among Several Genotypes of Extra Short‐Duration Pigeonpea (Cajanus cajan)

Abstract

Pigeonpea is a major global legume crop that provides nutrition and income for some of the world's poorest people. Global pigeonpea yields are constrained due to damage from flower‐ and pod‐feeding lepidopteran pests, particularly Helicoverpa armigera. In this study, we evaluated the tolerance of several extra short‐duration pigeonpea cultivars to simulated herbivory at peak flowering in Southern Queensland, Australia. In the first field experiment (involving nine cultivars), pigeonpea cultivars overcompensated in response to simulated herbivory, but in the second experiment (four cultivars), pigeonpea compensated. Although we intentionally selected cultivars that differed in important phenotypic traits (phenology, determinacy and architecture), cultivars did not differ in their tolerance to simulated damage in our field experiments. However, our results did vary across the two seasons over which the field experiments were conducted, indicating that crop growing environment affects plant tolerance. Plants in the first field experiment (which experienced less pre‐flowering rainfall) experienced greater phenological delay and overcompensated in response to damage, whereas in the second field season, plants only compensated for damage. Across both experiments, pigeonpea plants tolerated herbivory by the known tolerance mechanisms of phenological delay, compensatory growth and redirection of assimilates. This study contributes to a sparse literature on how pigeonpea plants tolerate pest damage. For successful pest management tactics to be developed for H. armigera and other flower‐feeding pests in pigeonpea (i.e., economic thresholds and pest‐tolerant cultivars), future research should determine the influence of environmental variables on the tolerance of pigeonpea to herbivore feeding.