Baseline Sensitivity Of Colletotrichum Spp.to Picoxystrobin And Its Resistance Risk Assessment

Colletotrichum spp.is one of the serious diseases on capsicum plant and production in China.Not only can it cause pepper seeding death,can harm the fruint,can cause fruint rot,but had a great influence on the yield and quality of pepper.At present,the chemical prevention are still take the important position in controlling the spread of Colletotrichum spp.Using the fungicides unreasonably has cause the Capsicum anthracnose became resistance and unsentivity.Picoxystrobin is belong to strobilurin fungicides and has been registered in American for prevention and control of pepper anthracnose,but it is still at the experimental stage in our contury.So far it is no report on the resistance research of Colletotrichum spp.to Picoxystrobin.Therefore,this research tested the sensitivity of Colletotrichum spp.to Picoxystrobin and the sensitivity baseline has been established.On this basis,the Picoxystrobin-resistant mutants were induced.The fitness,the biological characteristics and the physiological and biochemical characteristics of mutant-isolates were studied,aiming to provide a fundamental reference for the scientific and rational use of Colletotrichum spp.to Picoxystrobin.The main results are as follows1.To establish the sensitivity baseline of of Colletotrichum spp.to Picoxystrobin.The 45 Colletotrichum spp.isolates were collected,isolates and determined sentivity from the three of ShanXi JinZhong,where Picoxystrobin and the similar fungicides have not spayed.The result showed that the EC50 values range from 1.4041 ?g/mL to 16.6497 ?g/mL,and the mean value is 6.7831±3.4994 ?g/mL.The sensitivity frequency of the 45 isolates was distributed as a single peak cure.So,the EC50 values could be used as the relative baseline sensitivity of Colletotrichum spp.to Picoxystrobin.Salicylic acid oxime(SHAM)as main alternative oxidase inhibitors in bypass oxidation way.It can enhance the inhibitory effect to the mycelial growth and can generate a certain amount of compensation efficiency.When the concentration of SHAM is 150 ?g/mL,the determination of sensitivity of of Colletotrichum spp.to Picoxystrobin showed that the EC50 values range from 0.0221 ?g/mL to 0.2752 ?g/mL,and the mean value is 0.1090±0.058 ?g/mL.The compensation efficiency value in the bypass oxidation way was indicated that the lowest value is 6.0391,the hightest value is 301.4412,the mean value is 78.02622.To obtain the Picoxystrobin-resistant mutants by inducing in the laboratory.Three isolates were selected randomly in three collection sties and induced by ultraviolet irradiation,drug domestication and uv+drug separately.Eight Picoxystrobin-resistant mutants were obtain,which 6 mutants express the low level of resisitance and the other two ones is media resistance3.To determine the fitness and biological characteristics of resistant mutants.The determination to the fitness of resistant mutants indicated that the mycelium growth,spore production,pathogenicity,genetic stability were similar in comparison to the sensitive isolates.The influence of the nutrient conditions,pH value,temperature and the chemistry characteristics of picoxystrobin-resistant mutants and sensitive strains was determined.The results showed that the utilization of starch as carbon sources,ammonium nitrate as nitrogen source were the highest in both resistant and sensitive isolates,and both of them grow better in the neutral partial acid conditions,grow poor in the condition of strong acid or alkali.The optimum temperature for both resistant and parent isolates is 25?.In addition,the pressure sensitivity measurement results show that all isolates can grow well in all of glucose concentrations and the colony diameter will increase obviously in the medium containing glucose.For salt concentration,all isolates grow poor with the increase of salt concentration and both resistant and parent isolates are sensitive to high salt concentration of osmotic pressure changing4.To determine cross-resistance between picoxystrobin and azoxystrobin,kresoxim-methyl,carbendazim,SYP-Z048,Prochloraz.There was cross-resistance between picoxystrobin and azoxystrobin,kresoxim-methyl,which are belong to the Strobilurin fungicide.But there are not cross-resistance between Picoxystrobin and carbendazim,SYP-Z048,Prochloraz,because they have different mode of actionComprehensive analysis showed that Colletotrichum spp.is easily develop resistance to picoxystrobin.So on the production,picoxystrobin should be better use mixed with other mode of action fungicides to to delay or even prevent the development of resistance.