Evaluation of resistance in 16 eggplant genotypes to the two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae)

With more than 200 host plant species, the two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), is one of the most common and destructive pests of agricultural crops including vegetables, fruits, field crops and ornamentals in both open-field and greenhouse cultivations in Turkey. Control of this pest generally depends on the use of synthetic pesticides. The use of resistant plant varieties in conjunction with other control tactics generates more effective and sustainable results in management of many pests. In the present study, a total of 16 eggplant genotypes, including eight wild sources and eight standard commercial cultivars, were evaluated for the first time using free-choice and bridge test methods for their resistance against this mite under controlled conditions. Resistance was evaluated by counting mites settled on plants of each genotype. Resistance data were calculated by taking mean number (no.) of mites that prefer the plants of susceptible or resistant genotypes at each time interval (1, 3, 5, 7 or 9 days after releasing mites in free-choice tests; 30 min, 1, 2 or 3 h in bridge tests). The results from free-choice tests showed that wild genotype, Solanum sisymbriifolium (from INRA, France) was the most resistant genotype to T. urticae with no settlement of mites per plant both at 7 and 9 days after releasing mites, and followed by two commercial S. melongena genotypes (Topan 374 and Kemer) that had 2.25 and 2.50, 4.25 and 3.50 mites per plant, respectively, on the 7th and 9th days of mite introduction. S. sisymbriifolium was also found to be the most resistant genotype in bridge tests with a mean no. of 13.0 mites per plant. These results can be used for breeding and management purposes for control of two-spotted spider mite.