Investigation on resistance of different peach cultivars to two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae) in laboratory conditions

Two-spotted spider mite (TSSM), Tetranychus urticae Koch is an important pest of peach in Iran. This study was conducted to estimate the resistance of five peach cultivars (Redtap, G.H.Hale, Kardi, Elberta and Springtimes). Resistance of different cultivars to this pest was evaluated at 27 ± 1°C, 50 ± 10 %RH and 12 L: 12 D h., using leaf disk bioassay with introducing five adult female mites on leaf disk and counting number of eggs, mite mortality and host damage. Moreover, trichomes density on upper and underside of the leaves, concentration of phenolic compounds and percentage of leaf nutrients were measured. The results showed that the highest plant damage was on G.H.Hale and Kardi cultivars, and the lowest on Elberta, Redtap and Springtimes. The findings also indicated that the density of trichomes on upper and underside of the leaves was not significantly different among cultivars. Therefore, this parameter has no role in resistance to TSSM. Furthermore, there was no relationship between concentration of phenolic compounds and resistance to TSSM. Altogether results revealed that Redtap, Elberta and Springtimes were the most tolerant, whereas G.H.Hale and Kardi were the most susceptible cultivars and nutrient imbalance especially potassium is probably main factor of the resistance against TSSM.