Ecological Fitness of Non-vector Planthopper Sogatella furcifera on Rice Plants Infected with Rice Black Streaked Dwarf Virus

We evaluated the effects of rice black streak dwarf virus （RBSDV）-infested rice plants on the ecological parameters and its relevant defensive and detoxification enzymes of white-backed planthopper （WBPH） in laboratory for exploring the relationship between RBSDV and the non-vector planthopper. The results showed that nymph survival rate, female adult weight and fecundity, and egg hatchability of WBPH fed on RBSDV-infested rice plants did not markedly differ from those on healthy plants, whereas the female adult longevity and egg duration significantly shortened on diseased plants. Furthermore, significantly higher activities of defensive enzymes （dismutase, catalase and peroxidase） and detoxification enzymes （acetylcholinesterase, carboxylesterase and glutathione S-transferase） were found in WBPH adults fed on infected plants. Results implied that infestation by RBSDV increased the ecological fitness of non-vector planthopper population.

Susceptibility to Insecticides and Ecological Fitness in Resistant Rice Varieties of Field Nilaparvata lugens Stl Population Free from Insecticides in Laboratory

A population of rice brown planthopper （BPH） Nilaparvata lugens collected from a paddy field in Hangzhou was successively reared on susceptible rice Taichung Native 1 （TN1） in a laboratory free from insecticides for more than 14 generations. The changes in susceptibility to insecticides and ecological fitness on different resistant rice varieties were monitored in each generation. The resistance ratio to imidacloprid sharply declined with the succession of rearing generations without insecticides from 359.94-fold at F1 to 6.50-fold at F14 compared with the susceptible strain, and the resistance ratio to chlorpyrifos was from 9.90-fold at F1 to 5.94-fold at F14. Nymphal duration and weights of newly hatched female adults were significantly affected by rice variety, generation and their interactions, but nymphal survival was significantly affected by the generation only. The ratio of brachypterous adults in males was affected by the generation and generation × variety interaction, whereas no difference was found in females. Nymphal duration extended with increasing generations, and the female nymphal duration was shorter in the susceptible variety TN1 than those in the resistant varieties IR26 and IR36. In addition, the female adult weight in TN1 was higher than those in IR26 and IR36. These results indicated that the resistance of field BPH population to insecticides was reversed after several generations of no-exposure to insecticides, and the ecological fitness in TN1 was higher than those in IR26 and IR36. These findings suggested the rational and reduced use of insecticides in combination with the manipulation of resistant rice varieties would be effective for BPH management.

Influence of rice black streaked dwarf virus on the ecological fitness of non-vector planthopper Nilaparvata lugens （Hemiptera： Delphacidae）

Rice black streak dwarf virus （RBSDV） is transmitted by the small brown planthopper （SBPH）, Laodelphax striatellus （Fallen）. Non-vector rice brown planthopper （BPH）, Nilaparvata lugens （Stal）, shares the same host rice plants with SBPH in paddy fields. The changes in nutritional composition of rice plants infected by RBSDV and the ecological fitness of BPH feeding on the infected plants were studied under both artificial climate chamber and field conditions. Contents of 16 detected amino acids and soluble sugar in RBSDV infected rice plants were higher than those in the healthy ones. On the diseased plants BPH had significantly higher nymphal survival rates, nymphal duration of the males, weight of the female adults, as well as egg hatchability compared to BPH being fed on healthy plants. However, there was no obvious difference in female nymph duration, longevity and fecundity. Defense enzymes （superoxidase dismutase, SOD and catalase, CAT） and detoxifying enzymes （carboxylesterase, CAE and glutathione S-transferase, GST） in BPH adults fed on diseased plants had markedly higher activities. The results indicate rice plants infected by RBSDV improved the ecological fitness of the brown planthopper, a serious pest but not a transmitter of the RBSDV virus.

Indication of Genetic Linkage Map for Sunflower(Helianthus annuus L.) by SSR Markers

In order to investigate the possibility and efficiency of exogenous gene spread in nature and potential ecological risk of transgenic rice, as well as analyze the effect of exogenous Bt gene insertion on ecological fitness of transgenic rice plants, a experiment was carried out with three insect-resistant Bt transgenic rice cultivars Bt63, R1 and R2 and one conventional rice line 11-838 as experimental materials, the insect-resistant transgenic and non-transgenic rice plants were inter- cropped pair-wisely under high and low insect-infestation pressures, and the vegeta- tive growth, seed-setting and the resistance to rice stem borers were compared be- tween transgenic and non-transgenic lines. According to the experimental results, both the tiller number and fresh weight of Bt transgenic rice plants under low insect- infestation pressure showed no significant differences compared with the control, but the plant height, spike length and spike weight were all lower than those of non- transgenic rice plant, and Bt63 and R2 were significantly different compared with the control. On the contrary, under high insect-infestation pressure, the tiller number, spike length and spike weight of three Bt transgenic rice cultivars were significantly higher than those of the control, while the plant height showed different fitness ef- fects among various transgenic rice cultivars, which might be related to the charac- teristics of the receptive cultivars. The individual filled grain number and 1 000-grain weight of three transgenic rice cultivars showed no significant difference compared with the control under two different insect-infestation pressures, suggesting that the effect of exogenous Bt gene on seed setting was not significant. Under insect-infes- tation pressure, the resistance of three Bt transgenic rice cultivars against rice stem borer was significantly superior to non-transgenic rice, indicating that the effect of exogenous Bt gene on insect resistance of receptive plants was distinctly. Further- more, experimental results showed that the fitness cost of Bt transgenic rice was rel- atively low, which implied that exogenous Bt gene in insect-resistant transgenic rice might escape under certain environmental conditions, but this risk was very low.