Abstract: Effect of ten pepper varieties with different resistances on host selection was studied by releasing whiteflies (Bemisia tabaci) to the cage. In addition, physical traits of pepper leaves (trichome density, vascular bundle depth, wax content and leaf color) were investigated to explore the antiselection mechanism of pepper leaves to whiteflies. The results showed that the host preference of whiteflies was significantly different for the ten varieties and there were significant differences in leaf trichome density, vascular bundle depth, wax content and leaf color among the ten varieties. The population index of whiteflies was positively correlated with leaf trichome density, but negatively correlated with leaf vascular bundle depth and leaf color. There was no significant correlation between wax content and the population index of whiteflies. After 24hour release, the regression equations between population index (Y) and leaf trichome density, leaf vascular bundle depth, or leaf color were as follows: Y=0.632x+13.493 (r=0.953, P=0.000) for leaf trichome density, Y=-587.572x+449.035 (r=0.660, P=0.038) for leaf vascular bundle depth, and Y=-209.815x+259.088 (r=0.642, P=0.046) for leaf color. The multi-step regression equation of population index (Y) and trichome density (X₁), vascular bundle depth (X₂), leaf color (X₄) was as follows Y=0.583X₁+26.999X₂-56.126X₄+56.953, the respective path coefficients of the equation were P_X1→ Y=-0.879, P_X2→Y=0.030, P_X4→Y=-0.172. After 72hour release, there was no obvious correlation between leaf color and population index. These results indicated that at the early stage of host selection by whiteflies, leaf color played the major role; 72 hours later, however, leaf trichome density played the major role. Moreover, whiteflies had a similar trend of  host selection between spawning and feeding.

Key words: state transition, NPQ., photosystem, LHCⅡ phosphorylation