The spider mite Tetranychus turkestani (Acari: Tetranychidae) is one of the most important plant pests in the world, which causes significant damage to all kinds of field, garden, greenhouse and ornamental plants. Short life cycle and high fertility rate leads to a fast population growth in this pest. By feeding on the contents of the leaf mesophyll cells, this mite causes falling of the leaf and reduces photosynthesis drastically and generally has a negative effect on quality and quantity of the host plant. Due to the emergence of resistance to acaricides, it is necessary to use the other pest management methods for mites’ control. Inducing resistance by natural compounds is an alternative method or integrated approach for pesticides in order to control herbivores. Polyamins as plant growth regulators are effective in increasing resistance to biotic and abiotic stressors. In this research, the effect of polyamine spermine on the life table parameters of T. turkestani and determining the effective concentration of this compound in reducing the sensitivity of cucumber plants to this pest was investigated. The effect of this compound on the content of hydrogen peroxide, malondialdehyde, electrolyte leakage and the activity of ascorbate peroxidase and catalase enzymes under the influence of T. turkestani in cucumber plants was eva‎luated. Cucumber plants were treated with 1, 2 and 3mM spermine concentrations and in presence of T. turkestani. Cucumber plants were treated with 1, 2 and 3mM spermine concentrations and T. turkestani stress. The results showed the spermine concentrations used did not affect the length of the embryonic period. The longest duration of the larval period was seen in 3mM concentration whilst the shortest protonymph period was seen in 1mM spermine concentration. The length of third resting period was most in 2mM spermine treatment compare to controls. Treatment with 1 and 3mM spermine shortened the lifespan of adult mites and their entire life cycle. Amongst the spermine treatments, those who received 1mM spermine treatment showed higher ovulation period, fecundity rate, and gross and net reproductive rates compare to controls. Between examined groups those received 1 mM spermine treatment showed highest reproductive value peak, fecundity rate and life expectancy. The 2mM spermine treatment caused the shortest peak related to the survival rate and also the lowest range of fecundity and life expectancy for the mite. Different concentrations of spermine did not affect the pre-oviposition period and the total pre-oviposition period compared to the control. 2mM spermine treatment lowered both intrinsic and finite rate of population increase. The mean generation length was increased by all of the spermine treatments. Feeding of T. turkestani on cucumber plant increased the production of H2O2 and MDA, which was associated with an increase in ion leakage. With the increase in H2O2 production, APX enzyme activity increased and CAT enzyme activity was inhibited. Mites treated with 1mM spermine showed lower level of H2O2 content, MDA and ion leakage on the first, third and fifth days compared to mites in the control group. This treatment did not increase the activity of APX and CAT enzymes on the third and fifth days. The mites treated with 2mM spermine showed lower H2O2 and MDA content on day one and three compare to mites received other treatments. Also, the amount of ion leakage in 2mM spermine treatment was lower on the first, third and fifth day compared to the mites treated with other spermine treatments. The highest activity of antioxidant enzymes APX and CAT was related to 2mM spermine treatment up to day five. Changes in biological indicators, especially H2O2, at a concentration of 3mM is abnormal, and this concentration could be considered toxic. This study showed the concentration of 2mM spermine had the greatest effect in reducing the sensitivity of cucumber plants to T. turkestani.

لادن طلائي

مهديه غلامي

نفيسه پورجواد، محمد حسين اهتمام