Abstract: For wisely evaluating resistance difference of cotton varieties to cotton aphid Aphis gossypii, the development and population dynamics of cotton aphid on eight cotton varieties (SM3, SY321, LM19, LM18, GK12, ZM32, SGK321, ZM41) of four types were investigated by combining field test and the laboratory experiment including life table construction and reproduction ability observation. The results indicated that there were significant differences in population dynamics of cotton aphid on different cotton varieties (P<0.05), with that on ZM32 (Bt transgenic cotton) was the highest (297.81 aphids/plant), and that on SM3 (conventional cotton) was the lowest (76.88 aphids/plant). There were also obvious differences at the selectivity of cotton aphid on the four types of cotton (P<0.05), but this pest exhibited the highest selectivity to Bt transgenic cotton. Judged with the life parameters of the experimental populations of cotton aphid, there were also notable discrepancies in the developmental duration, survivorship and reproduction and other examined parameters of the cotton aphid on different varieties. Cotton aphid population attained the longest developmental duration (6.46 d) on SY321 (conventional cotton) and the shortest (5.75 d) on ZM41 (Bt and CpTI transgenic cotton), and the survivorship on ZM32 was the biggest (88.21%) and on SGK321 (Bt and CpTI transgenic cotton) the smallest (76.46%), but the innate capacity of increase (r_m) were the highest on ZM32 (0.3695) and the lowest on ZM41 (0.3389). In addition, female adults fed on LM19 (insect resistance hybrid cotton) (44.8) had greater potential to enhance their fecundity compared to those fed on SGK321 (33.51). Generally evaluated, cotton aphid had the highest fitness on Bt transgenic cotton, and the lowest fitness on Bt and CpTI transgenic cotton.

Key words: Cotton variety, Aphis gossypii, fitness, population dynamics, host selectivity