Study On The Population Distribution And Biological Characteristics

Chive maggots feeding on a wide range, can harm a variety of vegetables and is the enemy of chive production. At present, chive maggot was little studied in the biological characteristics. Without knowing the characteristics of chive maggot, chemical pesticides were widespreadly abused to control the maggots as result of environmental pollution and the high rate of pesticide residues in chive, which seriously threated to people’s health. The article placed Heilongjiang Province as the background, the population distribution of chive maggot was investigated in this province. Meanwhile, four families seven species of vegetables were utilized to feed the chive maggots and the age-stage, two-sex life table had been successfully constructed, which cleared the indicators of biological characteristics on seven kinds of host plants. Meanwhile, the cold-related genes were screened by taking advantage of the high-throughput gene sequencing technology and the cold mechanism was analyzed. The specific results are as follows:1.Two investigation points were established through literature and the actual survey in Ningan County and Hulan District in Heilongjiang Province. The yellow plate method was utilized to survey distribution and occurrence of maggots and found that chive maggots occur in th early April and end in mid-September. However, the chive maggots reached the peak among early May to mid-May, mid-June and mid-September. This rusult provides a good theoretical basis for preventing chive maggot.2.The growth and development effects of chive maggot were explored on different host plants, which clarified the potential harm host of the chive maggot in Heilongjiang Province. The four families seven kinds of host plants that were mainly planted in Heilongjiang Province were utilized to feed the chive maggot and constructed the age-stage two-sex life table. The results of the study show that Chinese chive maggot could complete the subculture in 7 kinds of host plants, but each growth index was significantly different. The total developmental duration of chive maggot reared on chive, onion and cucumber were shorter and were 25.63 days, 27.87 days, 25.18 days, respectively. The fecundity of single female reared chive reached the highest numembers with 87, followed by cucumber and green onions. The difference was significant comparing with other hosts, the survival rate also showed a similar regulation. In terms of different population parameters, the intrinsic growth rate(rm), net value ratio(R0) and the finite rate of increase(λ) were the biggest reared on chive except for the λ reared on cucumber, which showed the significant difference comparing with other hosts. In summary, the adaptability of chive maggot was the best reared on chive, followed by the welsh onion, cucumber, garlic, chinese cabbage and radish, the potatoes was the weakest.3. For probing the tolerance instars and limit temperature of cold-resistant of chive maggot, the survival rate and supercooling point of 4th instar larvae and pupae were measured under different temperature. The results showed that the supercooling point gradually reduced from 25℃ to 0℃ and gradually rised from 0℃ to-2℃. The survival rate of pupa was higher than the 4th instar larvae domesticated under low temperatures.4. The populations of cold acclimation and room temperature were cultured and the RNA transcriptome library was constructed. The sequencing and analysis were completed and 465 million data volumes were obtained, meanwhile, 47102 unigenes were assembled and 10695 differentially expressed genes were getted. 6486 unigenes were annotated to the GO classification. These results showed that RNA transcription of chive maggot had significant effects on low temperature treatment.5. The cold-resistant gene screening and functional analysis of chive maggot were completed. 47 cold-related genes were screened through functional annotation and were divided into nine categories, including t-complex polypeptide, cytochrome c oxidase subunit, Serine/threonine-protein kinase, trypsin-like protein, ubiquitin, heat shock protein 70, heat shock protein 90, ribosomal protein, actin, respectively. Genes related cytochrome c oxidase subunit were up-regulated. After regulated by the enzyme mechanism, this gene was involved in metabolism, promoted synthesis of small molecules, and completed the multiple freeze protection system mechanism for cold. Meanwhile, this gene and rest genes participated the multiple molecular defense mechanisms together to resist cold. Trypsin and serine protease trypsin-like protein that belonged the food utilize genes were involved in glycolipids transformation and fatty acid synthesis for withstanding cold. The ubiquities, TCP-1 and Hsp70 and Hsp90 participated the stress response to regulate the protein structure and small molecules accumulation against the cold. Actins were down-regulated, which regulated the skeleton genes to change cell membrane fluidity and hibernate to withstand low temperatures. However, the related genes of ribosomal protein were down-regulated to participate the cell growth or death. The multiple molecular defense mechanism was completed by regulating these genes up or down-regulated to resist cold damage. In short, chive maggot could resist cold through multiple freeze protection system and multiple molecular defense mechanism under low temperature.