Evaluation of sensitivity of 21 genotypes of canola to cabbage aphid(Brevicoryne brassicae L.) under field conditions in Uromia region

Cabbage aphid (Brevicoryne brassicae L.) is a serious pest of canola (Brassicae napus L.) in the world and host plant resistance is considered to be important. Therefore, 21 genotypes of canola were evaluated in a randomized Complete Blocks Design with three replications. The experiment was performed under natural field conditions in the West Azerbaijan province, in 2005-06. Evaluation of the genotypes was based on the infestation index calculated as follow: (Ii) = P×N×L in which P = percentage of infested plants per plot, N= average number of aphid population in one centimeter of infested plant stem, L= average infested plant stem length (cm). Than data of (Ii) was transformed by (Ii=0.5). The first aphid infestation was observed in mid may and continued till harvest time in late June. High trend of aphid infestation implied to the increase of aphid populations, however, a significant decrease of aphid infestation was observed in the last sampling at seed maturity stage. Different sampling data indicated significant differences in aphid infestation and the forth samples had the highest infestation index. Canola genotype: were classified into following four groups: 1-Resistant (Modena, Sunday, Opera, and sinatra), 2-Moderate resistant (Zarfam, Sahara, Okapi, ARG-91004, ARC-5, Orient Milena and ARC-2), 3- Moderate susceptible (SLMO46, Talent, Celisius, Elite, Dexter and Ebontie) and 4- Susceptible (Geronimo, Olpro and Licord).