Primarily Studies On Melanism And Phoxim Resistance In Spodoptera Exigua (Hübner)

Genetic regulation on body color of Spodoptera exigua (Hubner) was investigated. Reciprocal crosses between the black mutant strain and the wild strain were used to determine the inheritance of pupa body color. Body color of pupae and adults of the two strains was inherited stably. In cross experiments between the mutant strain and the wild strain, F₁ population had middle (brown) phenotype. In the F₂ generation, the ratio of the wild phenotype: the middle phenotype: the mutant phenotype was 1.04:2.02:1. In DF₁(F₁×wild strain) generation, the ratio of the wild phenotype and the middle phenotype was 1.1:1. In RF₁(F₁×mutant strain) generation, the ratio of the middle phenotype and the mutant phenotype was 1.1:1. Genetic experiments showed that the inheritance of the melanic character followed the Mendalian imcomplete dominance law. A single pair of genes regulated the melanic character.Polyphenoloxidase activities of different stages and the enzymatic kinetic constant of the mutant strain and the wild strain were detected. Among different stages of the mutant and the wild strains, the highest polyphenoloxidase activity appeared in the 5^th instar larva. The polyphenoloxidase activity of the mutant strain was 1.4 times as much as that of the wild strain. K_m of polyphenoloxidase did not have notable difference between the two strains. But the highest activity of the mutant strain was 1.5 times as much as that of the wild strain. The results indicated that melanization of the mutant strain was associated with enhancement of polyphenoloxidase activities.By phoxim resistance selection, mutant relative resistant strain (3.39 times) and wild relative resistant strain (4.31 times) were obtained, respectively. Resistance mechanism studies results indicated that AChE activities of both the mutant relative resistant strain and the wild relative resistant strain were higher than those of their corresponding susceptable strains, 1.35 times and 1.17 times, respectively. However, there were no notable differences in GSTs and CarE activities between the two relative resistant strains and the two corresponding susceptable strains.