Evaluation of Some Characteristics Affecting the Resistance of Fifteen Native Iranian Onions against Thrips tabaci L

This experiment was conducted in order to evaluate the resistance of fifteen native onion cultivars against Thrips tabaci. These cultivars consisted of Ghermez Azarshahr, Kazbar, Tarom, Shenat Abhar, Gholi Gheseh Zanjan, Sefid Qom, Sefid Khomein, Dorche Isfahan, Sefid Kashan, Meshkan Fars, Eghlid Fars, Sefid and Ghermez Neishabour, Sefid and Sooraty Kordestan. The cultivars were grown in a randomized complete block (RCB) design with three replications over two consecutive years. The number of Thrips, leaf temperature and color, leaf thickness, damage rate and leaf angle were all measured in this experiment. The results indicated that cultivars were significantly different in terms of the number of Thrips and the damage rate at the 1% level. Meshkan Fars, Sefid Kordestan and Sefid Qom cultivars were resistant and Sooraty Kordestan, Gholi Gheseh Zanjan cultivars were sensitive against Thrips tabaci. Also, the angle between the two central leaves of resistant cultivars (Sefid Kordestan and Sefid Qom) was considerably greater than the others. In the case of leaf temperature, color and thickness, the results showed no significant differences between cultivars. To control Thrips tabaci (especially in Iran) growers mainly use dangerous pesticides in large quantities. The usage of resistant cultivars is one of the major components in integrated pest management (IPM) for decreasing pesticides use.