| Shinazimycin?phenazine-1-carboxylic,PCA?is a highly effective,low-toxic,and safe biological fungicide,which has been currently registered for the control of sheath blight on crop rice.However,PCA owns poor phloem mobility on crops,which limits its use.In the early stage of our research group,a series of phenazine-1-carboxylic acid-amino acids conjugates were synthesized and found to have phloem mobility on caster bean.In this study,using PCA-L-valine conjugate?PCA-L-Val?and PCA-D-valine conjugate?PCA-D-Val?as test agents,and PCA as a control agent,the analytical method of compounds were established on wheat by ultra-high liquid chromatography-tandem mass spectrometry?LC-MS/MS?,and then their systemicity in wheat seedlings at different growth stages was studied.And the same time,their indoor fungicidal activities against the pathogens of wheat root rot?Bipolaris sorokiniana?and wheat stem rot?Fusarium pseudograminearum?were determined.The indoor fungicidal activity results showed that the introduction of amino acids can change the original activity of PCA.The activity results against Bipolaris sorokiniana showed that PCA-D-Val had the quivalent activity as that of PCA,with the inhibition rate of PCA-D-Val was 62.72%and that of PCA was 65.16%.However,the activity of PCA-L-Val was lower than that of PCA,and its inhibition rate was 11.85%.The results indicated that the different space configuration of the amino acid had different effects on the biological activity of the parent.However,these compounds hardly owned obvious activity against Fusarium pseudograminearum.A method was established to detect the content of the tested compounds in wheat using LC-MS/MS,and the methods of liquid-liquid acid-base extraction and C18 solid phase extraction were used for the sample pretreatment.The results showed that the concentration of the test compounds in the root,stems and leaves displayed a linear relationship with the detected peak area;Within the addition concentration range,the recovery rates of the addition in each part of the wheat were between 83.24%?94.21%;the coefficient of variation was within the range of 1.21%?11.51%;the minimum detection concentration was 1×10-3mg/kg;the minimum detection amount was 1×10-4mg/kg;which meeted the national pesticide residue analysis and detection standards.The systemicity of the PCA-valine conjugates in wheat seedlings at different growth stages was studied,and the results are as follows.For the wheat at the tillering stage,when the concentration of the tested agents was 200?M,the content of the compounds could be detected in the roots of the wheat,and the content of PCA-L-Val in the roots had the highest value of 15.50?mol/kg after treatment for 18 h,and that of PCA-D-Val reached the maximum value at the same time,which was 11.37?mol/kg.The results indicated that the PCA-valine conjugates had phloem mobility in wheat,and the activity of PCA-L-Val was stronger than that of PCA-D-Val.In addition,the conjugates could also be detected in the tiller leaves of wheat,and the content of PCA-L-Val in the tiller reached the maximum value of 8.74?mol/kg after treatment for 3 h,while PCA-D-Val reached the maximum value of 4.54?mol/kg at the same time.The results indicated that the PCA-valine conjugates had a particular systemicity from the main stem to the tillers,and the systemicity of PCA-L-Val was stronger than PCA-D-Val in wheat plant.However,the control agent PCA owns pool systemicity.For the wheat at the jointing stage,when the concentration of the tested agents was 200?M,the content of the conjugates could be detected in all parts of the wheat,and the content of PCA-L-Val in the lower stem reached the highest value of 3.9?mol/kg after treatment for 12 h,and that of PCA-D-Val reached the maximum value of 0.43?mol/kg after 48 h;The content of PCA-L-Val reached the maximum value of 9.19?mol/kg in the lower leaves after treatment for 6 h,and that of PCA-D-Val had reached the maximum value of 6.30?mol/kg after 24 h;PCA could't be detected in the lower stems and lower leaves of wheat.The results showed that the conjugates still had phloem mobility in wheat at the jointing stage,and PCA-L-Val had the better phloem mobility in the lower stalk than PCA-D-Val in plant.In addition,after treatment with PCA-L-Val and PCA-D-Val,the content of PCA could be detected in all parts of the plant in wheat plants at different growth stages,which indicated that some certain decomposition reaction occurred when the conjugates were absorbed by the leaves and then transported to all parts of the plant.And the specific metabolic mechanism will be further clarified.In summary,the coupling reaction using PCA with valine could improve or reduce the fungicidal activity of the parent,and could improve the systemicity in wheat seedlings.The different space configurations of the valine had different effects on the systemicity of the conjugates in wheat.And its systemicity mechanism in wheat will be study further. |
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