Roja Kianpour - Department of Entomology, Faculty of Agriculture, Tarbiat Modares University, P. O. Box: ۱۴۱۱۵-۳۳۶, Tehran, Iran.
Yaghoub Fathipour - Department of Entomology, Faculty of Agriculture, Tarbiat Modares University, P. O. Box: ۱۴۱۱۵-۳۳۶, Tehran, Iran.
Javad Karimzadeh - Isfahan Research Centre for Agriculture and Natural Resources, Isfahan, Iran.
Vahid Hosseininaveh - Department of Plant Protection, College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran.

The diamondback moth, Plutella xylostella (L.) is a serious and economically important pest of cruciferous crops worldwide. The nutritional indices of this pest on four host plants including two canola (SLM۰۴۶ and RGS۰۰۳) and two cabbage cultivars (Green-Cornet and Glob-Master) were determined under laboratory conditions (۲۵ ± ۰.۵ °C, ۶۵ ± ۵% RH and ۱۶: ۸ L: D h). The highest relative consumption rate (RCR) and relative growth rate (RGR) were recorded on RGS۰۰۳ (۹۵.۶۸ ± ۱۴.۵۲ mg/mg/day) and SLM۰۴۶(۰.۳۸۲ ± ۰.۰۴۱ mg/mg/day), respectively. The efficiency of the conversion of ingested food (ECI) and efficiency of conversion of digested food (ECD) were significantly higher on SLM۰۴۶ (۲.۲۹۸ ± ۰.۶۴۶ and ۲.۴۷۱ ± ۰.۷۱۹%, respectively). However, there was no significant difference among cultivars regarding approximate digestibility (AD) index. The highest feeding performance of the larvae of P. xylostella was found on SLM۰۴۶. The nutritional indices are appropriate tools in host plant resistance evaluation and they also could provide profound understanding of the behavioral and physiological bases of insect-host plant interactions.

nutritional indices, canola, cabbage, Plutella xylostella