Study On Biological Characteristics And Genetic Regularity Of Body Color Of Ectropis Grisescens Warren

Ectropis grisescens Warren is one of the major pests of tea plant, which widely distributed in almost all tea-producing provinces of China and tremendously influenced tea production. Besides, E. grisescens has differentiated into two kinds of body colors: grey and melanic types, but there has yet no relevant reports so far. In order to provide reference for primary production and reveal the inheritance of body color of E. grisescens, biological characteristics and genetic regularity of body color were investigated in this thesis based on field investigation and laboratory observation. The results are as follows:1. E. grisescens occurred 6-7 generations per year in Xinchang, Zhejiang province. The first generation of larvae occurred from late March to late April, and others occurred monthly. The pupae gradually began to overwinter in rhizosphere soil of tea from mid to late October and feathered in mid-March of the following year. The larvae have 4 or 5 instars. The total amount of food consumption was 736.2 mg per larva on average, and 96.01% was eaten by instar from 3rd to the last. The food consumption of larvae exponentially increased from 1st to last instar, and the exponential curve between food consumption(y) and larva instar(x) was y = 1.012e1.5857 x. Under the condition(24℃) of laboratory, the number of eggs was 291 per female. The survival rates of each stage of E. grisescens were as follows: eggs, 93.8%; 1st-3rd instar larvae, 98.6%; 4th-5th instar larvae, 98.6%; prepupae, 98.6%; pupae, 82.2%; and adults, 92.0%. The F1 generation sex ratio(♀:♂) was 1:0.85, and the population trend index was 98.9.2. The morphologic differences mainly showed on adults between grey and melanic type of E. grisescens, but there are no significant morphologic differences in the larvae, pupae and eggs. In body color, antennae, wings, thoracic legs, abdomen and other of adult, the differences are distinctly between grey and melanic type, of which the wing surface markings different most significantly. The fore and hind wings markings did not display on melanic type, which showed on grey type. The wing surfaces of melanic type are completely covered in black scales, and only nervures are visible obviously. Under the same environmental conditions, the developmental duration, survival rate of larvae, survival rate of generation, egg prodution, hatching rate, sex ratio and population trend index had no significant difference between grey and melanic type of E. grisescens. Compared with grey type, the body length and weight of mature larvae and food consumption of melanic type are reduced, indicating that the competition ability of larvae of melanic type was weak. In addition, In terms of mating choice, mating mode between grey type and melanic type is randomly without preference.3. Under the condition of 21~23 ℃, the survival rates of prepupae, pupal and generation, egg prodution and population growth index were both higher of grey and melanic type, which significantly decreased with the temperature drops or rises, and lowest at 27 ℃. This result indicated that the suitable environmental temperature for growth of E. grisescens was 21 ~ 23 ℃, and the growth were hindered with lower or higher temperatures, of which the affect of higher temperature was particularly serious on normal growth and reproduction of E. grisescens. Within the scope of the 19 ~ 27 ℃, the growth and development of melanic type accelerated significantly when less than 21℃, what’s more, the developmental threshold temperature decreased significantly of larval and pupal stage of melanic type, indicating that the cold resistance of melanic type is stronger. When up to 27℃, population growth index of melanic type decreased significantly, indicating that the resistance to higher temperature of melanic type was poor.4. Based on classical genetic hybridization experiments, we found that the trait of body-color inherited stably of E. grisescens. The melanic trait is dominant, and grey is recessive. A pair of alleles in autosoma controlled the trait of body-color, and the inheritance pattern of body-color followed Mendelian segregation laws.