The Control Efficacy And Mechanism Of Selenium With Fungicides On Rapeseed Sclerotinia Stem Pot And Pear Anthracnose

Selenium is an essential trace element,as helpful to human body health,and it can promote crop growth,increase crop quality.Sodium selenite as a selenium source,not only can be absorbed by plants,but also inhibit the effect of disease.Rapeseed sclerotinia dtem pot is the first major disease of rapeseed,which has occurred in the major production areas in China,seriously reducing the yield and quality of rapeseed,resulting in economic losses.Pear anthracnose was one of main diseases on pear trees,often occurring in pear fruit storage period,can cause large quantities of fruit rot.With the aggravation of global climate and environment change,the harm of the disease is more and more serious.In order to ensure the quality and safety of agricultural products,it is urgent to study a new control way.The chemical control is the common prevention and treatment of two diseases,but the use of chemical agents will bring environmental and food safety and many other issues.This paper studies control effect of selenium on rapeseed sclerotinia dtem pot and pear anthracnose.The study rom the determination of selenium and selenium compound and toxicity of fungicides on the pathogen,the effects of selenium and selenium with fungicide compound on control of disease,the safety evaluation of crops and so on.These studies provide technical support for green control,pesticide reduction and functional agricultural production.The main results are reported as follows:1.The control effect of selenium and fungicide on rapeseed sclerotinia dtem potThe inhibitory effects of sodium selenite and fungicide on Sclerotinia sclerotiorum were studied by indoor toxicity measurement method.The results showed that sodium selenite had inhibitory effect on mycelium of Sclerotinia sclerotiorum,and its EC₅₀0 was 113.9651μg.mL^-1.The inhibitory effect of the fungicides on the mycelium of Sclerotinia sclerotiorum were better than that of carbendazim,phenazino-1-carboxylic and pyraclostrobin,and the EC₅₀0 were0.0121μg.mL^-1,0.1773μg.mL^-1,0.6387μg.mL^-1,0.8695μg.mL^-1.The choices of carbendazim,phenazino-1-carboxylic acid and pyraclostrobin with sodium selenite were compounded,in which sodium selenite and phenazino-1-carboxylic acid were combined with A and B or sodium selenite with carbendazim combination A,on the inhibition of Sclerotinia sclerotiorum mycelium synergistic effect.The study on the effect about disease spots spread inhibits of sodium selenite and its mixture on sclerotinia to two rapeseed varieties,the effect of the second application was significantly different from that of the first application.In the Wanyou 13 rapeseed varieties,the highest control effect ofsodium selenite can reach 48.72%after he first application.The highest control effect was the combination of sodium selenite and phenazino-1-carboxylic was 3:2 combination,the highest control can reach 67.35%after the first application,the second application can reach 63.24%.In Dezayou 5 rapeseed varieties,the highest control effect of sodium selenite can reach 28.46%after he first application,and the second application was31.65%.,the highest control effect of sodium selenite with phenazino-1-carboxyliccan combination can reach 25.27%after he first application,and the second application was 35.52%,The activities of PPO,POD,and the content of MDA in rape were changed after treatment with sodium selenite.Theactivities of CAT was not changed much.These enzymes and MDA were related to the disease resistance of plants,indicating that sodium selenite can induce rape disease resistance.2.Safety evaluation of selenium rich rapeseedThe treatment concentration of sodium selenite had different effects on the germination and emergence rate of rapeseed,on the root of the rape and bud length are toxic effects,indicating that selenium can not be used to irrigate,with soil and other means.Sodium selenite on the rapeseed growth test showed that spraying240μg.mL^-11 and 480μg.mL^-11 concentration of sodium selenite on the rapeseed has a phytotoxicity,but the old leaves can be repaired,leaves can not,spraying should be avoided seedling stage.Sodium selenite in spraying rape flowers early,with the increase of the concentration of sodium selenite,the selenium content of rapeseed were becoming more and more high,but were within the safety standards.Combined with the research results show that the production of selenium-rich rapeseed,should avoid applying selenium watering,with soil,also should avoid spraying selenium in seedling stage,cause the damage to rapeseed.It should choose initial spraying selenium,both to produce selenium-rich rapeseed,but also to control rapeseed sclerotia,for the production of functional agriculture to provide a theoretical basis.3.The effects of selenium and fungicides on pear anthracnoseThe inhibitory effects of sodium selenite and fungicide on Colletotrichum gloeosporioides were studied by indoor toxicity measurement method.The results showed that sodium selenite had inhibitory effect on mycelium of Colletotrichum gloeosporioides,and its EC₅₀0 was 137.6037μg.mL^-1.The inhibitory effect of the fungicides on the mycelium of Colletotrichum gloeosporioides were better than that of pyraclostrobin,tebuconazole and difenoconazole,and the EC₅₀0 were0.05397μg.mL^-1,0.2.2006μg.mL^-1,0.6760μg.mL^-1.The effect of sodium selenite and fungicides on the mycelial growth of Colletotrichum gloeosporioides was studied,it is found that the combination of sodium selenite and tebuconazole 1:1 had a synergistic effect on the inhibition of mycelium.The effects of sodium selenite and its combination on the control of postharvest pear anthracnose disease were studied by spraying and soaking,the results showed that the mixture and sodium selenite were used in the treatment of postharvest pear anthracnose disease had a control effect,but the soaking effect was better than spraying effect.Among them,150μg.mL^-11 sodium selenite were soaked for 2h,the control effect reached 23.72%,and the highest control effect of spraied were 21.40%.Control effect of Sodium selenite and tebuconazole mixture were soaked could reach about 90%,spraied about 15%.4.Effects of selenium on main enzyme activity in pear fruitAfter soaked,sodium selenite could obviously improve the activities of CAT and POD on pear,and the activities of PPO was not very obvious.The activities of CAT,POD,PPO were highest on the third day when selenium after inoculation of pear fruit.Those were higher than those of other groups.After 6 days,the three kinds of enzyme activities tend to balance,indicating that selenium was related to the disease resistance.5.Safety evaluation of selenium rich pearThe distribution of selenium in pear epidermis and pulp was determined under the concentration of 40μg.mL^-11 sodium selenite.Surface as a result,the highest content of selenium in the epidermis,including the selenium content of the pear fruit skin which 40μg.mL^-1sodium selenite were 1.515μg.g^-1,about 10 times higher than selenium content in contrast.In the pulp,selenium content were significantly less than the epidermis,and with the pear nucleus closed to the content of selenium would be lower and lower.The content of selenium in the pulp tissue of 40μg.mL^-1sodium selenite were soaked in pear fruit in 0.143μg.g^-10.449μg.g^-1,which accorded with the safety standard of selenium-enriched food.