| For a long time,the damage of aphids to wheat has been an important obstacle to limiting wheat yield and quality.At the present,insecticides are commonly used to control the damage of aphids to wheat.However,the abuse of pesticides also kills a large numbers of non-target insects.This situation not only damages the farmland ecosystem seriously,but also leads to the farmland and crop pesticide residues exceeding seriously,which is a huge threat to human food safety.In recent years,Potassium can be found to improve the resistance of crops,especially in improving the resistance to wheat aphid resistance,that is particularly significant.However,the research on the increase of wheat resistance to aphid by potassium is mostly limited to the study of potassium and other basic metabolites of nutrient and secondary substances in wheat,while the effect of potassium on wheat resistance to aphid resistance and the relationship between potassium and aphid infection-induced phloem defense response and the regulation of potassium on the signal pathway induced by aphid infection in wheat are relatively inadequate,which is not conducive to a comprehensive understanding of potassium in the plant to enhance the role of resistance to aphid.Based on the above reasons,this study used EPG technology,plant tissue frozen section technique and fluorescence quantitative PCR technique to study the effect of potassium supply on wheat aphid resistance and its physiological mechanism,and provided the scientific basis for the ecological control of wheat aphids.In this experiment,Solution culture was used in the experiment and four potassium levels were applied(0.01,0.1,2,10 mmol /L KCl,respectively).When the wheat grow to four leafs,electrical penetration graph(EPG)technique was used to record aphid’s feeding behavior.At the same time,the four leaves of wheat were infected with aphids,and then frozen sections of plant tissue were used to observe the deposition of callose in the phloem of the leaf before and after infection.On the basis of this,the K0.01 and K2 wheat levels were used as the research object to study the effects of GSL2 and GSL10 on the synthesis and degradation of callus in wheat under the condition of aphid infection in wheat with potassium deficiency and normal potassium leave,GSL12 and BG,and the expression of AOS,EIN2 and PAL associated with JA,ET and SA.The results are as follows:(1)The EPG waveforms of wheat leaves on the aphids fed with different potassium levels showed that:in the non-probe phase,on the K2 and K10 levels of wheat leaves not only aphid penetration time significantly slower than K0.01 and K0.1 level,but also the total time and the mean time of non-probe wave of the former were significantly higher than the latter.In thestylet pathway phase,the duration timeof path waves C wave andmechanicalobstacles waves F wave which showed the penetrating behavior on the K2 and K10 level were significantly longer than the K0.01 and K0.1 level.In thephloem-feeding phase,the time point of first E1 wave start,the time point of first E2 wave start,the percentage of time E1 accounts for the total E wave,total time of E1 periods,mean duration of E1 wave,sum time of E1 without E2 wave followed all above parameters increased with the increase of potassium level among K0.01 to K2 levels,but there were no significant difference among various potassium levels in the former three indicators and when further raised the level of potassium to K10,there were significant differences between K0.01 and K10;however,there were significant difference between K0.01 and K2 in the latter three indicators and when further raised the level of potassium to K10,although each index continued to increase,there were no significant differences between K2 and K10;total time of E2 wave decreased with the increase of potassium level among K0.01 to K2 levels,but there were no significant difference among various potassium levels,but when further raised the level of potassium to K10,it would be further reduced and there were significant difference between K0.01 and K10.In the-feeding phase,the-feeding G wave was the longest in K0.01 level of wheat leaf by aphid,and with the increase of potassium level G wave duration decreased significantly.(2)The study that phloem callose was caused by aphid infection of wheat leaves with different potassium levels showed that there was callose deposition in the phloem of wheat leaves when there was non-aphid infection,but the area and the ratio of callose deposition to the total area of phloem accounted for a small proportion.After infecting with aphids,we found that the callose was deposited in the phloem.Among them,the callose area and area ratio of K0.01-K2 were significantly increased with the increase of potassium level.After removal of the aphids that infested the wheat leaves,we found that the callose in the leaves of K2 and K10 was restored to the area where the aphid infested wheat callose was deposited 48 hours after the removal of the aphids,and K0.01 and K0.1 were still slightly higher than those without aphid infection at 72 hours after removal of the aphids.Fluorescence quantitative analysis of four genes related to the synthesis and degradation of callose showed that the expression levels of GSL2,GSL10,GSL12 and BG were not high when there was no aphid infection,and there was no significant difference between different potassium levels.When GSL2,GSL10 and GSL12 genes were used,the expression level of normal potassium was higher than that of potassium deficiency,while the BG gene was 48h-72 h after aphid infection.The expression of BG gene in wheat was higher than that in normal potassium.(3)The regulation of potassium phosphate-related genes induced by aphids in wheat infected with aphids showed that the normal potassium levels could significantly increase the aphid infection relative to the AOS,EIN2 and PAL genes in wheat.The expression of related genes was observed,and the expression of genes at two adjacent time points was relatively stable.At the same time,the study also found that when the wheat was in the potassium deficiency state,AOS,EIN2 and PAL genes showed synergies,and the synergistic effect between AOS and EIN2 was obvious.When the wheat was in the normal potassium level,the EIN2 and PAL genes showed synergistic effect in the early stage of aphid infection,while the AOS and PAL genes showed a short antagonistic effect in the early stage of the aphid infection. |
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