The Changes Of The Population And Preliminary Study Of The Mechanism In Nilaparvata Lugens After Feeding On Fungicides Treated Rice Seedlings

The use of fungicides can affect the growth and development as well as reproduction of brown planthopper(BPH)Nilaparvata lugens Stal.In order to determine the effects that BPH feeding on the fungicides treated rice seedlings.Three fungicides,hexaconazole,trifluzamide and azoxystronbin were selected for study.The BPH were feeding on the fungicides treated rice seedlings,then the life table of BPH popupation was built and the contents of oxalic acid,reducing sugars and soluble proteins in the rice seedlings were measured.1.Developmental dynamics of BPH population after feeding on fungicides-treated rice seedlingsThe life table of BPH popupation was built after feeding on the fungicides treated rice seedlings.The results showed that feeding on japonica rice seedlings treated with recommended dose of fungicides significantly extended developmental duration of the 3 instar nymphs and feeding on glutinous rice seedlings treated with high dose of fungicides significantly extended developmental duration of the 5 instar nymphs and the full life developmental duration,as well as the female longevity.There is no significant difference in BPH between the population feeding on the glutinous rice and on japonica rice seedlings treated with recommended dose of fungicides.The population doubling time,average generation time,index of population trend and relative fitness in BPH population increased after feeding on glutinous rice seedlings treated with high dose of fungicides,while the index of population trend and relative fitness in BPH population decreased after feeding on japonica rice seedlings treated with high dose of fungicides.2.Changes of biochemical and physiological substances of rice seedlings after treated with fungicidesIn order to determine the effects of the rice seedlings treated with fungicides,contents of oxalic acid,reducing sugars and soluble proteins in the rice seedlings were investigated.The results showed that the contents of reducing sugar in glutinous rice seedling treated with high dose of fungicides significantly decreased,C/N ratio also decreased but not significantly compared with the control.There is no significant difference about the contents of three physiological and biochemical substances in glutinous and japonica rice seedlings treated with recommended dose of fungicides,as well as japonica rice seedlings treated with high dose of fungicides.While,the C/N ratio in rice seedlings treated with recommended dose of fungicides decreased and increased in rice seedlings treated with high dose of fungicides,but not significantly which compared with control.3.The expression analysis of vitellogenin in female of BPH feeding on fungicides-treated rice seedlingsqRT-PCR was carried out to determine the expression of Nlvg in BPH female individuals at the first,the second and the third day after emergence.Our findings showed that the Nlvg expression of BPH in female individuals after feeding on glutinous treated with recommended dose of fungicides were higher than control at the first and the second day after emergence,significantly increased at the second day,and the Nlvg expression of BPH feeding on glutinous treated with high dose of fungicides were always higher than control.The Nlvg expression of BPH in female individuals feeding on fungicides-treated japonica rice seedlings were higher than control at the first day after emergence,and decreased at the second and the third day after emergence,were lower than the control at the third day after emergence.Taken together,the results indicated that there is no significant effects on BPH population after feedling on the rice seedlings treated with recommended dose of fungicides.Glutinous treated with high dose of fungicides is conducive to the growth of BPH,while japonica after the treatment of high dose of fungicides is not conducive to the growth of BPH.The futher study for Nlvg gene expression of BPH feeding on glutinous rice seedlings treated with recommended dose of fungicides and feeding on japonica rice seedlings treated with fungicides.