ارزيابي تحمل به تريپس (Thrips tabaci Lindeman) در ژنوتيپ پياز سفيد اصلاح شده خمين و چند رقم رايج پياز ايراني

Evaluation of Resistance to Thrips (Thrips tabaci Lindeman) in Improved Sefid-e-Khomein Genotype and some other Iranian Onion Cultivars

Thrips tabaci is one of the most important pests causing serioues damages on onions in Iran despite several chemical sprayings. To assess the population density and damage of the thips on onion, Improved Sefid-e-Khomein genotype along with seven other Iranian cultivars of onoin were planted in a RCB design with four replications in two separate experiments (sprayed and non-sprayed) in Arak for three years (2001-2003). The control field was also planted by ten meters distance and sprayed with current insecticide in order to reduce thrips damages. The highest number of thrips were counted on Ghermez-e-Azarshar, Sefid-e-Shahroud and Ghermez-e-Shahroud cultivars (27.6, 25.7 and 25.3 thrips per plant, respectively) and the lowest on numbers were recorded on Sefid-e-Qom and Sefid-e-Kordestan (16.01 and 15.8, respectively). Amount of damage was highest on Ghermez-e-Azarshahr and the lowest Sefid-e-Kordestan and Sefid-e-Qom cultivars. In non-sprayed plots, the highest yield was recorded for Sefid-e-Kashan and Sefid-e-Qom cultivars (79.2 and 75.1 tha"1, respectively) and the lowest yield for Sefid-e-Kordestan cultivar (61.0 tha"1). Based on the average density of thrips, average damages and curling scores and average yield in sprayed and non-sprayed plots, the Improved Sefid-e-Khomein genotype was found to be tolerant to the thrips.