J Pest Sci (2009) 82:163–170 DOI 10.1007/s10340-008-0235-8 123 ORIGINAL PAPER Evaluation of resistance in 14 soybean genotypes to Tetranychus urticae (Acari: Tetranychidae) Amin Sedaratian · Yaghoub Fathipour · Saeid Moharramipour Received: 11 June 2008 / Revised: 27 October 2008 / Accepted: 5 November 2008 / Published online: 25 November 2008  Springer-Verlag 2008 Abstract The eVect of 14 soybean genotypes (Sahar, Sari, Williams, Tellar, Hill, Clark, Tms, Dpx, Zane, 032, 033, L 17 , Ks3494 and I27) on life history and fecundity of two-spotted spider mite (TSSM), Tetranychus urticae Koch, was investigated. All experiments were conducted at 28 § 1°C, 65 § 5% r.h. and a photoperiod of L16:D8 h. The highest development time was 8.41 and 8.78 days for male and female on I27, and the lowest value of this period was obtained on Sahar and Ks3494 for male and female, respectively (7.11 and 7.60 days, respectively). The TSSM fecundity varied from 33.62 to 153.82 eggs per female, which was minimum on 032 and maximum on L 17 . The comparison of TSSM biological parameters on diVerent soybean genotypes and cluster analysis of these parameters demonstrated that Ks3494, 032, Dpx and Sahar were the most resistant genotypes to this pest. An antibiosis process could be, at least in part, the cause of this variation. Knowl- edge of the extent of susceptibility or resistance of geno- types and biology of a pest on a crop are fundamental components of integrated pest management (IPM) pro- grams for any crop. Implication of these observations in the control of TSSM on soybean is discussed. Keywords Antibiosis · Plant resistance · Soybean · Tetranychus urticae Introduction Soybean (Glycine max (L.) Merrill) is one of the most important and widely grown oil crops in the world, and commercially produced in Golestan, Mazandaran and Moghan regions of Iran. Among the wide range of pests which attack this crop, two-spotted spider mite (TSSM), Tetranychus urticae Koch, is one of the most important pests, and its population has increased enormously in the diVerent soybean-producing areas of Iran and other coun- tries around the world. This mite infests the underside of leaves, where it produces profuse webbing. TSSM feeds using a piercing–sucking process that damages plant cells and tissue. This behavior leads to the appearance of yellow chlorotic spots on leaves (Martinez-Ferrer et al. 2006). The short life span, high fecundity and its ability to develop resistance to many acaricides have made chemical control of this mite particularly diYcult (Luczynski et al. 1990). Because of the harmful eVect of the residual toxicity of the chemical pesticides on humans and environment, control methods with comparative safety are being searched by the entomologists (Naher et al. 2006). One strategy for sustainable management of TSSM to minimize development of pesticide resistance is that of host- plant resistance. Host-plant resistance can be an useful com- ponent of an integrated pest management (IPM) system that is compatible with other methods of control, such as chemi- cal control, and it may make management factors, such as beneWcial natural enemies, more eVective (Lorenzen et al. 2001). In addition, in many cases, even partial resistant cul- tivars are useful to enhance the eVects of biological control agents (Hare and Andreadis 1983; Bong et al. 1991). Detailed information on sources and mechanisms of host-plant resistance to speciWc insect species is the Wrst step in developing an insect-resistant cultivar (Jyoti et al. Communicated by C. Cutler. A. Sedaratian · Y. Fathipour (&) · S. Moharramipour Department of Entomology, Faculty of Agriculture, Tarbiat Modares University, P.O. Box 14115-336, Tehran, Iran e-mail: fathi@modares.ac.ir