| Plant diseases are one of the main reasons for the reduction of grain output and income,and have a serious impact on food security,human health,economic and trade and other aspects.At present,the control of plant diseases is still mainly based on chemical control,which can bring obvious and effective control effects in a short period of time.However,due to long-term unreasonable use,the control effect of chemical agents is significantly reduced and risk of environmental pollution,health of human and animal is caused.In recent years,natural-derived fungicides compounds have attracted the attention of plant protection workers due to their good antifungal effect,novel mechanism of action,environmental friendliness,low residue and easy degradation,safety and low toxicity to non-target organisms;Combined application of multiple drugs with the aim of improving the efficacy,reducing the dosage,and reducing environmental pollution,it reduces the cost of medication,reduces the harm caused by chemical drugs to humans and nature,and brings people new ideas for the prevention and control of plant diseases.Based on previous research,this paper evaluated antifungal activity of 20 small molecule phenolic compounds against common plant pathogenic fungi such as Sclerotinia sclerotiorum,Magnaporthe oryzae,Rhizoctonia solani,Fusarium graminearum,and Botrytis cinereal,etc..Then,explored their preliminary mechanism of action.The binary composition of crytolepine and its analogues with small molecular phenolic compounds;the binary composition of hinokitiol,plant essential oil and its main components have been evaluated for their anti-agricultural pathogenic fungi and mold activity.Through the above research,we hope to discovery high activity Compounds and binary compositions.The main contents are described as follows:Chapter 1: Introduction This chapter first briefly describes the ani-phytopathogenic fungi activity of small-molecule phenolic compounds.At the same time,we summarized the antifungal mechanism of small-molecule phenolic compounds from five aspects: destroying cell membranes,destroying cell walls,affecting energy metabolism,affecting mitochondrial respiration,and inducing host defense mechanisms.Finally,the research and prospects of combination drugs in the resistance to agricultural pathogens are also summarized accordingly.Chapter 2: Study on the antifungal effect and mechanism of natural and synthetic phenolic compounds on phytopathogenic fungiPreliminary studies have shown that small-molecule phenolic compounds have good antifungal activity.In this chapter,20 phenolic compounds such as thymol and carvacrol were screened for antibacterial activity,and we found that6-tert-butyl-m-cresol was effective against Fusarium graminearum.EC50 value was3.20 μg/m L,which was significantly higher than azoxystrobin（EC50 = 8.12 μg/m L）.Therefore,we chosed Fusarium graminearum as the target.The mycelia treated with6-tert-butyl m-cresol were observed through morphological observation and determined the integrity of the cell membrane,permeability.and internal preliminary studies on its mechanism of action were carried out by experiments such as mitochondrial membrane potential,ROS,nuclear morphology,malondialdehyde content,hydrogen peroxide content,and mitochondrial Ca2+ content.At the same time,the effect of 6-tert-butyl-m-cresol on the content of DON and its biosynthesis-related genes（Tri5,Tri6）was found to be the effect of 6-tert-butyl-m-cresol on DON.Finally,The combined application of 6-tert-butyl m-cresol and carbendazim aims to find the best antifungal composition,reduce the dosage of carbendazim,and further improve the antifungal activity.The results showed that 1).6-tert-butylm-cresol might take mycelium membrane and mitochondria as the target to increase the peroxidation degree of mycelium cells,and eventually induced cell apoptosis to play an antibacterial role.2).The content of DON was reduced by influcing gene Tri5 and Tri6.3).When 6-tert-butylm-cresol was mixed with carbendazim at the mass ratio of2:3,it had a synergistic effect on F.graminearum,and the SR value was 1.89.Chapter 3: Study on synergistic effect of cryptolepine,neocryptolepine and phenolic compounds and cinnamaldehydeDue to the long-term unreasonable use of chemical drugs,bacteria and fungi have developed different degrees of resistance to these chemical fungicides,and then increasing the amount of fungicides can achieve the desired sterilization effect,resulting in increased drug residues and increased toxic and side effects.In order to cope with this resistance,reducing the amount of chemical fungicides,combination medication is particularly important.In this chapter,the main agents was cryptolepine and neocryptolepine.thymol,carvacrol,6-tert-butyl m-cresol,2-isopropyl phenol,2-tert-butyl phenol,2,4-Di-tert-butylphenol are auxiliary agent,the main and auxiliary agents are at a mass ratio of 1:1,1:10,1:20,1:50,1:100,and they are used in combination to prevent Fusarium graminearum,magnaporthe oryzae,Fusariu oxysporum,Botrytis cinerea,Sclerotinia sclerotiorum and Rhizoctonia solani.The results showed that cryptolepine had more complex value than neocryptolepine..Especially when the mass ratio of cryptolepine and 2-isopropylphenol is 1:50,the SR value is 39.75 on Sclerotinia sclerotiorum.In the composition of neocryptolepine,the SR value is 5.61 at a mass ratio of 1:1 with thymol on Botrytis cinerea.Based on the above research,we chosed cryptolepine as the main agent,paeonol,bakuchiol,eugenol,cinnamaldehyde,vanillin,and ferulic acid were used as the adjuvants,according to the mass ratio of 1:10,1:30,1:50,1:100,used in combination to control Fusahum graminearum,magnaporthe oryzae,Phytophthora capsici,Botrytis cinerea,Sclerotinia sclerotiorum and Rhizoctonia solani.The results showed that the combination of cryptolepine and eugenol had a significant synergistic effect on Sclerotinia sclerotiorum.The SR value was as high as 6.27 when the mass ratio was1:10.Chapter 4: Study on synergistic effect of hinokitiol,plant essential oil and its main componentsHinokitiol is a natural monoterpenoid compound extracted from the cypress tree.It has antibacterial,anti-oxidant and anti-tumor effects.It is a highly safe plant extract.Essential oil（EO）is a general term for volatile oily liquid substances with aroma（and/or fragrance）extracted from plant tissues such as roots,stems,leaves,flowers,fruits,seeds,branches or exudates.Studies have found that essential oils and single components have strong properties of inhibiting or killing microorganisms such as bacteria and fungi.Accordingly,this chapter uses hinokitiol as the main agent,oregano essential oil,clove essential oil,thyme essential oil and their respective main active ingredients carvacrol,eugenol,and thymol as auxiliary agents,and the mass ratio is 1:1,1:10,1:30,1:50,two-by-two combined application to control Fusarium graminearum,magnaporthe oryzae,Fusariu oxysporum,Botrytis cinerea,Sclerotinia sclerotiorum,Rhizoctonia solani and Aspergillus flavus.The results showed that the combination of hinokitiol and three essential oils against S.sclerotinia was more prominent,and the SR values were as high as 41.69,27.28 and 14.81 at the mass ratio of 1:1,respectively. |
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