Thrips tabaci Lind. is an important pest of Alliacea crops, such as Tareh Irani or Persian leek (Allium ampeloprasum Tareh group). This is a native leafy vegetable grown in the most regions of Iran. This study has been done to estimate the amount of resistance to thrips, in 14 Tareh Irani landraces. Damage factors and some morphological traits, including divergence angle of the plant’s innermost leaves, leaf thickness, sheath length, quantity of leaf wax and also amounts of some metabolites including water-soluble carbohydrates, total phenols and pungency were measured. The results showed significant difference between landraces for thrips resistance (p < 0.05). Principal component analysis elucidated the influence of measured traits on resistance potential to onion thrips, whilst cluster analysis classified Tareh Irani landraces into three groups: resistant, susceptible and highly susceptible. There was negative significant correlation between divergence angle of the innermost leaves and total phenols with the amounts of damage, while the amount of water-soluble carbohydrates correlated positively with thrips damage, implying that these characters are very important and should be considered in screening thrips resistance across Tareh Irani landraces.
