Measurement of grass grub resistance of bean in a controlled environment

Abstract

Controlled environment conditions were used to compare growth of individual third instar larvae on bean (Phaseolus vulgaris L.) — the roots of which contain phaseollin, a highly active feeding deterrent to larvae of grass grub, Costelytra zealandica (White) — with that on lotus (Lotus pedunculatus Cav.) and white clover (Trifolium repens L.) as resistant and non-resistant controls respectively. After 28 days, 94.6% of larvae were recovered undamaged. Larval weight gain on bean (78 mg) indicated that bean is resistant relative to white clover (108 mg gain) but not as resistant as lotus (62 mg gain). Extracts from roots were examined in toxicity and feeding deterrent bioassays and in chemical analyses. The use of controlled environment conditions provided a sensitive method for measuring resistance of plants.

Keywords:

• Costelytra zealandica
• grass grub
• Phaseolus vulgaris
• Lotus pedunculatus
• Trifolium repens
• plant resistance
• insect feeding deterrents
• insect toxins
• isoflavonoids
• phaseollin
• controlled environment