Liu Kuanyu

A modified one-step procedure for rapid RNA isolation from insect

A modified guanidinium isothiocyanate method was used to extract total RNA from two forest insect species Clostera anastomosis and Saperda populnea. The integrity of RNA was demonstrated by the methods of gel electrophoresis and cDNA analysis. Typical A260/A280 absorbance ratio of the total RNA was in range of 1.8 to 2.0. The size of double strand cDNAs obtained by RT-PCR was more than 2 kb, which indicated that intact mRNA was obtained. The fragments of β-actin and chitinase gene from the RNA of C. anastomosis were obtained by RT-PCR, which indicated that the RNA could be used for other molecular operation. By this procedure, RNAs could be extracted and analyzed by electrophoresis from at least 8 samples within 4 hours. These results showed that this method was time-and cost-saving and effective.

Causes of outbreak of the larch caterpillar (Dendrolimus superans Butler) in Daxingan Mountain and its control strategy

In 1991, in Daxingan Mountain, an outbreak of larch caterpillar (Dendrolimus superans Butler) happened on large areas of more than one million hectares, where stands of larch were seriously damaged because needles on the trees were almost eaten up by the pest, causing enormous economic losses. Analysis of data collected indicated that the main cause of the outbreak of larch caterpillar on large areas was that, after thirty years of exploitation, mature and overmature forests decreased rapidly, middle-aged and young forests incresed in large amount, significant changes occurred in individual ecological conditions of stands, especially those tended, with decreasing canopy density and better light condition in the forest, and all these were adventageous to the outbreak of the pest. In addition, in recent years, the climatic condition in Daxingan Mountain changed significantly. The yearly average temperature raised gradually and the soil surface temperature in April and October increased year by year, which were advantageous to the outbreak of larch caterpillars. In short, the significant changes in the ecological conditions in Daxingan Mountain provided suitable conditions for the outbreak of the larch caberpillar, and after several years of increase in population number, the larch caterpillar outbroke into a serious disaster on vast areas. In the paper, composite control strategy was also discussed.

THE CLONING, SEQUENCING AND EXPRESSION OF THE LdMNPV POLYHEDRIN GENE

Abstract  LdMNPV ‐ NEFU isolate collected from the forestry farm of Northeast Forestry University was purified and the genomic DNA of MMNPV was extracted. The LdMNPV polyhedrin gene was cloned by PCR. The results showed that the sequence was an open reading frame (ORF) of 735bp capable of encoding 245 amino acids. The polyhedrin gene sequences of the MMNPV‐NEFU isolate and a Canada strain, MMNPV‐G differed in 5 bases. The polyhedrin gene of the LdMNPV‐NEFU isolate contained C, G, T, C and G at 54, 109,379, 508 and 701 sites from the start codon, but the LdMNPV‐G isolate contained G, C, C, T and T at the corresponding sites respectively. The same amino acids were encoded by the two ORF sequences, with the exception that Asp and His are encoded by GAC on the polyhedrin gene sequence of the LdMNPV‐NEFU isolate and by CAC in the MMNPV‐G isolate. The MMNPV polyhedrin gene was expressed in E. coli BL21 (DE3) by the pT7–7 plasmid vector.

Population characteristics ofDendrolims superans in Daxing’an Mountains

Dendrolims superans produced one generation every two years. Large larvae and small larvae exist at the same time. It broke out in Daxiang an Mountains in 1990, and seriously destroyed growth ofLarix gmelini Rupr. In order to controlD superans, the population properties ofD superans were studied from 1991 to 1992, including sexratio, age distribution, pattern etc.. The sex ratio ofD. superans population is ♀∶♂ − 1.06:L. The larvae age distribution indicates that larvae over 5 instar is less than younger larvae under 4 instar in Yongqing forest farm, but the younger larvae under 4 instar is more than larvae over 5 instar in Hanjiayuanzi Forest Farm. The population ofD. superans in Yongqing Farm has been declining. and mereasing in Hanjiayuanzi. Pupae and eggs are mainly distributed in middle and lower crowns layer of trees respeetively account for 66% and 59.5% of total individuals. The pupae in higher crown layer is lightly regular distribution and clumping distribution middle and lower crowns layer of trees. The eggs in higher crown is light clumping distribution and random in middle and low crown of tree.

Quantitative dynamics of larch caterpillar (Dendralimus superans [Buller]) and the biological control

The relationship between pest population and other factors is rather complex within the forest ecosystem. A number of environmental factors, such as extreme climatic conditions, infection of natural enemies, may cause the death of pest insects directly. The effect of these factors reflects basically the situation and cause of death of insects at different stages of entire process of growth and development, so that they may be employed as the basic records of the quantitative dynamic of the population, and are of important value to the study of population quantitative dynamics of pests. Since Morris and Miller (1954) applied the life table technique to study natural population of insects, the insect life table technique has becoming an important means for the study of quantitative dynamics of pest populations. In foreign countries, the study of the life table of forest pest began in 50 year’s already. Moreover, the results of investigation were applied to the productive practice, such as the spruce budworm (Chorisloneura fumiferana Clemens), winter moth (Opperophlera brumata Linnaeus), while in our country, the quantitative dynamics of many forest pests were not investigated. The larch caterpillar is one of the great pest of larch plantation in China. Every year, the outbreak of this pest occur in some places, causing large economic loss. Many studies were performed on the biological and chemical controls, but the investigation on quantitative dynamics of the natural population of larch caterpillar was lacking. Since 1980, we studied the quantitative dynamics of the natural population of larch caterpillar in Shangzhi County, Heilongjiang Province and worked out life tables of two generations.

A preliminary study on the biology ofCydia illutana dahuricoiana in the northeast of China

The tortricid moths damdging Dahurian Larch (larix gmelini Rupr.)cone were surveyed in a matural larch forest in Wurjihan in the eastern parrt of Inner Mongolia, China from 1988 to 1989, and the population dynamics of the moth is investigated in Kuduer, Jiwen and other neighbor areas. The tortricid moth was identified to beCydia illutana dahuricolana (V. I. Kuznetzov), the first recored in China. It has one generation a year, and overwinters in pupae in the eastern part of Inner Mongolia. The characteristics of the larvae and pupae are descrbed in detail, its life habit and damaging are preliminarily studied. The differences of its occurence in different areas are disscussed by combining with meteorological factors.