Research On The Damage Of Echinochloa Crus-galli And The Difference Between Resistant And Susceptible E.crus-galli Transport Quinclorac In South Paddy Fields Of Guangxi

Echinochloa crus-galli（L.）Beauv,Poaceae Barnhart,an annual herb,is one of the most important malignant weeds in paddy fields,which seriously affects the yield and quality of rice.The hormone herbicide quinclorac is the effective drug for controlling barnyard grass in paddy field,but the resistance of barnyard grass to quinclorac is becoming more and more serious when it is used in large dose for a long time.In order to clarify the occurrence of barnyard grass and its resistance to quinclorac in south paddy fields of Guangxi,in this study,a systematic investigation was conducted on barnyard grass in paddy fields in southern Guangxi from 2019 to 2020,and the status of resistance to quinclorac was analyzed.At the same time,the difference in the transport capacity of susceptible and resistant barnyard grass to quinclorac caused by aquaporin was investigated,which provided a theoretical basis for the comprehensive management of resistant barnyard grass.The main results are as follows:1.A total of nine species of Echinocloa species were found in the paddy fields of Baise,Beihai,Chongzuo and other south rice fields of Guangxi,including five species of Echinocloa,such as Echinochloa glabrescens,Echinochloa colonu,Echinochloa caudata,Echinochloa cruspavonis,Echinochloa glabrescen,and 4 varieties of Echinochloa crusgalli var.mitis,Echinochloa crusgalli var.zelayensis,Echinochloa crusgalli var.praticola,Echinochloa crusgalli var.breviseta.Among the nine Echinocloa species observed,E.crusgalli var.mitis showed the largest niche breadth（2.85）,E.colonum showed the minimum niche breadth（0.46）.In Baise,Qinzhou and Wuzhou,E.crusgalli var.mitis was mono-dominant among Echinocloa species on rice fields,while in Beihai,Chongzuo,Guigang,Nanning and Yulin,E.crusgalli var.zelayensis was dominant species.2.The resistance of Echinocloa to quinclorac was different in south rice areas of Guangxi,most areas have developed high resistance to quinclorac.The resistance rate in Yulin,Nanning,Guigang and Wuzhou was more serious,and the frequency of resistance was more than 50.00%,while in Baise was only5.56%.The whole plant showed that there were 55 barnyard grass with high resistance,among which Nanning and Guigang accounted for more.The GR₅₀value of the most resistant barnyard grass was 14864.86 g a.i./ha,and the resistance index was 451.51,there was 1 barnyard grass with low resistance and the most sensitive barnyard grass GR₅₀value was 32.92 g a.i./ha,the resistance index was 1.3.The shoot of selected susceptible and resistant barnyard grass were applied at the recommended registered dose（300 g a.i./ha）of quinclorac.Results showed that the susceptible and resistant barnyard grass MDA content in shoot and root were compared with controls are increased rapidly,and in shoot the susceptible barnyard grass MDA content was higher than that of in resistant barnyard grass,after 3 d of quinclorac treatment,the MDA content of susceptible barnyard grass was 2.83 fold of resistant barnyard grass.In root,the MDA content of susceptible barnyard grass was 1.60 fold than that of resistant barnyard grass after 5 d of quinclorac treatment,indicating that susceptible barnyard grass was damaged greatly.In order to reduce the damage caused by MDA,the activities of SOD,CAT and GST in susceptible and resistant barnyard grass shoots and roots increased first and then decreased,but the activities of after being decreased,and were basically higher than susceptible barnyard grass.After 5 d of quinclorac treatment,the activities of SOD,CAT and GST in resistant barnyard grass shoots were 1.99,2.62 and 3.26 folds of susceptible barnyard grass,and in resistant barnyard grass roots were 4.80,3.31 and 1.14fold of susceptible barnyard grass,respectively,indicating that resistant barnyard grass had strong oxidase activity thus reduced the damage of quinclorac.4.At the recommended dose（300 g a.i./ha）registered with the application of quinclorac in the shoots,the residue of quinclorac in the shoots of susceptible and resistant barnyard grass gradually decreased with the increase of treatment days,and the content of quinclorac in the roots both increased gradually,indicating that barnyard grass could transport quinclorac from the shoots to the roots.The residue reduction rate of quinclorac in the shoot of resistant barnyard grass was higher than that of susceptible barnyard grass,and the content of quinclorac detected in the roots of resistant barnyard grass was also higher than that of susceptible barnyard grass.After 5 d of quinclorac treatment,the residue content of quinclorac in the shoot of resistant barnyard grass was 85.25%of susceptible barnyard grass,and the content of quinclorac detected in the roots was 2.1 fold that of susceptible barnyard grass.These results showed that resistant barnyard grass had strong transport capacity for quinclorac.Transcriptome data showed that there were 308 differentially expressed genes that performed transport function,and aquaporin-related genes had the highest enrichment degree in resistant barnyard grass,and aquaporin-related genes had the highest enrichment degree.With the increase of qionclorac treatment time,the expression levels of PIP1;1,PIP2;4,PIP2;5 and TIP2;2 in susceptible barnyard grass were gradually inhibited,which were 79.89%,58.09%,10.64%and 45.07%of the control group after 5 d of quinclorac treatment,respectively.The expression levels of PIP1;1,PIP2;4,PIP2;5 and TIP2;2 in resistant barnyard grass were almost always higher than the control,and after 5 days of application,the gene expression levels of PIP1;1,PIP2;4and TIP2;2 were 1.20-,1.11-and 1.67-folds of the control,respectively.With the addition of aquaporin inhibitor（Hg Cl₂）,the growth of susceptible and resistant barnyard grass shoots were inhibited by the application of quinclorc compared with only quinclorac treatment,and the expression levels of PIP1;1,PIP2;4,PIP2;5 and TIP2;2 genes in susceptible and resistant barnyard grass were also significantly inhibited,but the expression of PIP1;1,PIP2;4,PIP2;5genes in resistant barnyard grass was basically higher than that in susceptible barnyard grass.After 1 d,2 d,3 d and 5 d application of Hg Cl₂,the residues in susceptible barnyard grass shoot were 2.93-,3.01-,1.65-and 2.02-folds of that in quinclorac treatment group,respectively,and the quinclorac concent in roots were 34.61%,17.65%,41.91%and 2.5%of that in the control,respectively.The content of quinclorac in resistant barnyard grass shoot was 3.07-,2.85-,1.67-and 1.33-folds,respectively,and the content of quinclorac in roots was 42.62%,26.26%,13.70%and 70.23%,respectively,but the content in resistant barnyard grass roots was still higher than that in susceptible barnyard grass.These results indicated that Hg Cl₂increased the sensitivity of barnyard grass to quinclorac,and decreased its transport capacity by inhibiting aquaporin.At the same time,by inhibiting aquaporin,the transport capacity of quinclorac was decreased,and the high expression of PIP1;1,PIP2;4 and PIP2;5 in resistant barnyard grass may be the reason for the stronger transport capacity of quinclorac compared with susceptible barnyard grass.