Resistance of hybrid canola ( Brassica napus L.) to flea beetle ( Phyllotreta spp.) damage during early growth

Abstract

The hybrid canolas, Brassica napus hyb. K4-87 and B. napus hyb. K36-87, were tested for two modes of resistance, antixenosis and tolerance, against flea beetles, Phyllotreta spp. In feeding tests in which choices were offered between the hybrids and a standard inbred canola cultivar, B. napus cv. Westar, the cotyledons of the hybrid K4-87 and the cotyledons and first true leaves of the hybrid K36-87 showed a higher level of antixenosis. As neither parent of K36-87 had a higher level of antixenosis, this trait in the hybrid may be due to heterosis. In no-choice feeding tests, however, cotyledon damage and seedling biomass 1 week after feeding damage did not differ among K4-87, K36-87, and Westar. The hybrids showed no tolerance to feeding damage either in the laboratory or in the field. On the basis of plant biomass and yield data from Manitoba and Saskatchewan, the hybrids do not exhibit sufficient resistance to provide protection in the field. These results do not support the hypothesis that hybrid canola will contribute an agronomically useful level of resistance against flea beetle damage under commercial growing conditions.