Antibiosis resistance of 13 clones of Populus spp. to poplar leaf aphid (Chaitophorus populi Koch) in East Azarbaijan

   Poplar leaf aphid, Chaitophorus populi Koch (Hemiptera: Aphididae) is one of the important sucking pests that cause direct and indirect damage on poplar trees (Populus spp.) in Iran and East Azarbaijan province. In this study antibiosis resistance of 13 poplar clones belonging to the three species against poplar leaf aphid under laboratory conditions (25±2 ˚C, 55 ± 5% relative humidity and 16L: 8D h photoperiod) was investigated in 2008. Ten rooted cuttings of each clone (with 20 cm long and 1.5 cm in diameter) were used for testing. By releasing one-day-old nymphs on cuttings, the process of their life until natural death of adult aphid such as establishment, feeding, developmental time, survival rate, pre-reproductive time and the number of progeny was determined. After collecting the necessary data, intrinsic rate of natural increase (r_m) was calculated. The ANOVA of results indicated that there is significant difference among the effects of poplar clones on r_m. Based on compared r_m means, all five clone of white poplar, P. alba due to having higher r_m-values (0.271 to 0.302) were susceptible clones to the aphid and among them, P. a82.5 with the highest r_m was the most susceptible clone of P. alba species. Among the P. nigra clones,  p. n82.4,  p. n82.8 and p. n56.12 were more susceptible to the pest, respectively. While p. n82.7 and p. n62.154 clones were relatively resistant to pest. Finally, two others (p. n62.191 and p. n82.6 clones) with the only one clone of P. euramericana, given the minimal impact on r_m-value (0.0591 to 0.0717) were determined as the most resistsnt among tested clones.