| Spodoptera frugiperda is a major agricultural pest that has invaded China in recent years and has spread to most parts of the country,posing a great threat to food production security.DIMBOA is a extenstive secondary metabolite widely existed in gramineous plants.It has strong biological activity and has certain inhibitory and toxic effects on many phytophagous insects,plant pathogens,weeds and other harmful organisms.In the breeding process of maize insect resistance,the content of DIMBOA is an important index of maize insect resistance.However,there are few reports on the effects of DIMBOA on the growth,development and physiological metabolism of fall armyworm.In this paper,firstly,the extraction technology of maize leaves DIMBOA was optimized.Secondly,the degradation rate of DIMBOA in the artificial diet of fall armyworm was determined,and the change of maize leaves DIMBOA contents after fall armyworm infestation were studied.And then the feeding selectivity of fall armyworm larvae to different concentration of DIMBOA diets were studied.Finally,the effects of different concentrations of DIMBOA diets on the growth and physiological metabolism of fall armyworm were studied.The main results are as follows:1.The degradation rate of DIMBOA in the artificial diet at 4℃ was significantly lower than that at normal temperature(25℃).The content of DIMBOA decreased by 5.5% and 27.4%after 1 days,22.0% and 45.8% after 2 days,28.7% and 69.2% after 5 days,respectively.2.After the 5th instar larvae of S.frugiperda damaged corn leaves for 2,4,6,and 12 hours,there was no significant difference in the content of DIMOBA in corn leaves compared to the control.After 24 hours of damage,the DIMBOA content significantly decreased.The selection rate of the 3rd instar larvae of S.frugiperda feeding on different concentrations of DIMOBA diets for 4,6,and 8 hours was significantly lower than that of the control,and the selectivity disappeared after 16 hours of feeding.3.After 48 hours of feeding with different concentrations of DIMBOA diets,the weight gain of the 3rd and 5th instar larvae of S.frugiperda showed no significant difference compared to the control.However,the weight gain of the 5th instar larvae significantly decreased after feeding with 1.0 mg/g DIMBOA diets.Compared with the control group,there were no significant changes in the developmental time,pupal stage,pupation rate,pupal deformity rate,pupal weight,eclosion rate,adult oviposition period and adult longevity of S.frugiperda larvae after feeding on different concentrations of DIMBOA diets.However,there was a significant decrease in egg production and no obvious peak oviposition period.Except for a significant decrease in the survival rate of the first instar larvae,there was no significant change in the survival rates of other instars.4.The POD activity of S.frugiperda larvae significantly increased when feeding on different concentrations of DIMBOA diets for 48 h,72 h and 96 h.The CAT activity significantly increased at 72 h and 96 h after feeding on different concentrations of DIMBOA diets.The GST activity was significantly increased at 24 h,48 h,72 h and 96 h after feeding on different concentrations of DIMBOA diets.At 72 h and 96 h,the Car E activity increased significantly.The Ach E activity was significantly inhibited when fed with different concentrations of DIMBOA diets for 72 h.The Trypsin activity was significantly inhibited when fed with different concentrations of DIMBOA diets at 12 h,24 h and 48 h.In conclusion,DIMBOA has certain adverse effects on the growth,development and reproduction of S.frugiperda,but this insect can reduce the impact of DIMBOA through its physiological metabolism,improve its adaptability,and complete population expansion and reproduction.The research results are not only of great important significance for in-depth understanding of the defense mechanism and ecological adaptability of rapid invasion of S.frugiperda,but also provide a theoretical reference for the breeding work of insect-resistant varieties. |
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