The Ecological Adaptability And The Analysis Of Genetic Structure By RAPD-PCR In The Different Geographic Populations Of Asian Corn Borer, Ostrinia Furnacalis (Guenée)

In this paper, the ecological adaptability and genetic structure of different geographic populations of Asian corn borer (ACB),Ostrinia furnacalis (Guenee) from 13 locations in different ecological areas for corn growing throught China were carried out in laboratory. The following aspects were concentrated: a) the influence of different photoperiod and temperature combinations on the diapause induction in different geographic populations of ACB to ascertain the difference of diapausing characteristic among the geographic populations from different locations, b) cold hardiness and the survival ability of diapause and non-diapause larvae of different geographic populations under low temperatures, c) the infection of the main parasitical natural enemies on the overwintering ACB larval survival, d) analysing the genetic structure variation and DNA diversity of the 13 geographic populations by using RAPD-PCR. Main results were summarized as follows:1. Under the different combinations of photoperiod and temperature, the percentages of diapaused larvae in the geographic populations were different. The critical photoperiods for inducing ACB larval diapause were different in the geographic populations. Under low temperature(20 C) and short-illumination (11h13min) condition, larval diapause was induced in all tested populations and the percentage of diapause ranged between 98% and 100% but under high temperature(27 C) and short-illumination (11h13min) condition, diapause decreasing levels were different in populations. On the whole, the percentage of diapaused larvae decreased gradually from the north to the south with a range of 56.04%-97.89%. High temperature (27 C) and long-illumination (13h47min) had no advantage in inducing diapause and under that condition the percentage of larval diapause ranged between 30.12% and 68.16%. Moderate temperature and long-illumination, which leaded to the lowest diapause rate with a range of 0%-35.89% in all tested populations, were most suitable condition for the growth and development of the ACB. The northern populations have a longer critical photoperiods than the southern population at thesame temperature, and meanwhile, the photoperiodic thresholds could became short if temperature got high. Under 20癈 and 23.3 C and 27 C, the critical photoperiod of Guangzhou population from Guangdong in the South China was 14 h 7 min, 13 h 53 min, 12 h 58 min, respectively, but that of Jixi population from Heilongjiang in the north China was 15 h 24 min, 14 h 45 min, 14 h 15 min, separately. All of the results indicated that photoperiod affected the larval diapause of ACB combined with temperature.2. The resuscitation development duration (RDD) of overwintering larvae in different geographic populations became shorter gradaully from the nouth to the south aera following the latitude from high to low. It was shown that the ecological adaptability of ACB has developed among populations from different locations. By comparing the early stage of pupation of all tested populations, it was took 47 d to find first pupa for northern population from Jixi after resuscitation but only 7 d for southern population from Guangzhou. It is indicated that different geographic populations of ACB come into the stage of diapause in different periods and have different times from the beginning of the diapause to the temination and developing to pupae. Each populatin had its particular characteristics on the distribution of the resuscitation development duration (RDD). The RDD curves of overwintering larvae of Jixi population in Heilongjiang and Shenyang population in Liaoning have a high pupation peak because of massive pupation in short time but Guangzhou population in Guangdong have not obivious pupation peak because of discontinuously pupation.3. The SCP (supercooling point) and low temperature survival were tested for diapaused (artificially induced) and non-diapaused larvae of different geographic populations of ACB. The lowest temperature of SCP apparatus was improved from -24 C to -35 C. Th...