| Ostrinia furnacalis is a major maize pest in China, and it mainlydamage maize leaves, female spike and stem, and has caused serious damage to corn.DIMBOA(2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one), an important secondarymetabolite of maize, which are extensively exist in gramineous plants，and related tothese gramineous plants resistance to many insect pests and diseases. It has beenreported that the induced effect can stimulate plant start defense reaction andsynthesize secondary metabolites; DIMBOA could affect the growth of O. furnacalis,and the content of DIMBOA in corn varieties is also related to anti-borer resistance.Hence, the content of DIMBOA is an important index of resistance breeding.However, systematic study of the relationship between defense capabilities of maizevarieties following different extrinsic factors induction and the resistance to O.furnacalis, hasn’t been reported. whether DIMBOA content increase followingdifferent extrinsic factors induction and whether DIMBOA content changes after thedamage of O.furnacalis worth further exploration. This paper systematically studiedthe differences of DIMBOA content in maize leaf after mechanical damage. Insectfeeding and simulation feeding. It also examined the growth indexes of pupa, adultand changes of protective enzyme activity and detoxifying enzyme activity of theO.furnacalis larvae fed with induced maize leaves. In order to investigate therelation between the induced defense of host plants and the growth and anti-defensecapacity of O. furnacalis. The main results are as follows:(1) The induction DIMBOA content of Xundan20by different treatment wasmeasured, the results showed, in mechanical damage induction treatment group, theDIMBOA content of maize leaves after12h induction by mechanical damage is thethe highest, and significant higher than other treatments and contrast except that after24h induction. Comparing different damage degree, DIMBOA content in8holes isthe highest which is significant higher that in6holes and contrast, but has no significant difference with that in4holes. In insect herbivory treatment group andsimulation insect herbivory treatment group, the DIMBOA content difference wasnot significant.(2) The5th instar O.furnacalis larvae weight, pupal weight, pupal period andemergence rate received a certain influence when these larvae fed with maize leavestreated by different induction methods. In general, with the increasing DIMBOAcontent induced by extrinsic factors, O.furnacalis larvae weight, pupal weight andemergence rate decreased,while pupal period prolonged. This trend was particularlyevident in mechanical damage treatment group, followed by insect feeding treatmentgroup, the simulation insect herbivory treatment showed the least apparent trend.(3) We determine the activity of3main protective enzymes, including SOD,POD and CAT, in O.furnacalis larvae which were maintained with maize leavestreated by different inducing treatment. Results showed that larvae fed with maizeleaves induced by mechanical damage, comparing different inducing time, activityof SOD and CAT was the highest after12h induction. Activity of POD after3h,12hand48h induction was signicantly higher than the control and other inducingtreatments, however, there is no significant difference among these3inducing time.Comparing different damage degree,3enzymes activity is the highest induced by8holes damage and significant higher than other inducing treatment and untreatedcontrol, beside that CAT activity between8holes and6holes damage have nosignificant difference. Fed Larvae with leaves induced by insect herbivory,comparing different inducing time, SOD and POD activity of O.furnacalis larvae isthe highest after3h induction, while CAT activity is the highest after12h inductionthan other inducing treatment and untreated control. Comparing of different numberof inoculated insects, all3enzymes activity were the highest in that induced by2larvae herbivory treatment, and significant higher than the untreated control andother inducing treatment. O.furnacalis larvae maintained with maize leaves inducedby simulation insect herbivory, comparison of different inducing time, SOD activityis significant higher than the untreated control and other inducing treatment; PODactivity is the highest after24h induction, while there is no significant difference compared with3h induction, POD activity is significant higher than the untreatedcontrol and other inducing treatment; POD activity is higher after3h,6h,12h and24h induction than that48h induction and control, however there is no significantdifference among these4inducing time. Comparing of different simulation damagedegree, SOD and CAT activity induced by4holes is significant higher than theuntreated control and other inducing treatment; POD activity induced by3differentdamage degree is higher than control, but there is no significant difference amongthese3inducing treatment.(4) We determine the activity of3main detoxification enzymes, including GST,AchE and CarE, in O.furnacalis larvae which were maintained with maize leavestreated by different inducing treatment. Results showed that the larvae maintainedwith maize leaves induced by mechanical damage, comparing of different inducingtime, activity of GST and CarE is the highest after12h induction, is significantlyhigher than the untreated control and other inducing treatment; activity of AchE issignificantly lower than untreated control. Comparing of different damage degree,activity of GST and CarE is the highest induced by8holes compared to othertreatment and untreated control; activity of AchE is the lowest compared to untreatedcontrol. Larvae were fed with leaves induced by insect herbivory, comparison ofdifferent inducing time, GST activity of O.furnacalis larvae is the highest after48hinduction. CarE activity is the highest after3h induction; AchE is the lowestcompared with untreated control. Comparing of different number of inoculatedinsects, activity of GST and CarE induced by2larvae herbivory is significant higherthan the untreated control and other inducing treatment; activity of AchE issignificant lower than untreated control. O.furnacalis larvae maintained with maizeleaves induced by simulation insect herbivory, comparison of different inducing time,GST activity is significant higher after24h induction than the untreated control andother inducing treatment; CarE activity is significant higher after6h induction; AchEactivity is significant lower than the untreated control. Comparing of differentsimulation damage degree, GST activity induced by4holes is significant higher thanthe untreated control and other inducing treatment. CarE activity induced by6holes is significant higher than the untreated control and other inducing treatment; AchEactivity is significant lower than the untreated control.(5)After mechanical damage induction, the12h expression of bx1gene whichregulates and control the synthesis of DIMBOA in corn leaves is significantly higherthan control treatment group, while at other time points, it is significantly lower thanthe control. Also, after mechanical damage induction, the3h,6h and12h expressionof bx2, bx7, bx9gene are significantly higher than control treatment. And at othertime points, they are lower than the control. The expression of bx4gene wassignificantly higher than the control at all time points. |
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