Does Epidermal Thickness Influence White Cabbage Resistance against Onion Thrips (<i>Thrips tabaci</i>)?

Abstract

Present studies were made to investigate the association between epidermal thickness and resistance of white cabbage against onion thrips, Thrips tabaci Lindeman, 1889 (Thysanoptera: Thripidae). Six white cabbage varieties including three susceptible (‘Green Gem’, ‘Hurricane’ and ‘Quisor’) and three resistant to onion thrips (‘Balashi’, ‘Bloktor’ and ‘Riana’) were involved in the studies. Additionally, the extent of antixenotic resistance during head formation and the level of thrips damage at harvest were also assessed and compared between varieties. A higher density of onion thrips was observed on susceptible than on resistant varieties. The results indicate that the epidermis is of the same thickness in susceptible white cabbage varieties as in resistant ones; therefore, we conclude that the thicknesses of either the adaxial or the abaxial part of the epidermis of head-forming leaves is not responsible for cabbage resistance to thrips. The study thus confirms that antixenotic resistance of white cabbage to thrips is not determined by epidermal thickness.