Study On Metabolites Of Rhizoctonia Solani In Potato

The isolation,purification,biological activity,structural identification and degradation of Rhizoctonia solani metabolites in potato were mainly investigated in this paper.Firstly,the R.solani was cultured,and its metabolites were isolated and purified.Secondly,the biological activities of R.solani isolates obtained by isolation and purification were determined.The structure of R.solani toxins were preliminarily identified by ultraviolet absorption spectrum(UV),infrared absorption spectroscopy(FT-IR)and gas chromatography-mass spectrometry(GC-MS).Finally,the R.solani toxins were degraded by glow discharge plasma(GDP),and the effect of GDP on toxins was analysed.The results showed as:(1)In this study,organic solvent extraction method was used to extract the metabolites of R.solani,the optimum extractant for extracting the metabolites of R.solani was optimized by measuring the pathogenicity of the extract on potato tubers.The optimum extractant for extracting the metabolites of R.solani was ethyl acetate.Five R.solani isolates(T1、T2、T3、T4、T5)were obtained by isolating and purifying with methods of thin layer chromatography(TLC)and column chromatography(CC).(2)The wounds of wheat leaves treated with R.solani isolates T1,T2 T3,T4 and T5,the results showed that all the isolates could cause the lesion of wheat leaf wound,and the degree of T1,T2 and T3 was more serious.Potato seedlings were treated with T1,T2 and T3,the results showed that T1,T2 and T3 could induce the activities of POD,SOD and chitinase,the accumulation of MDA content and the cell membrane permeability of the leaves increased.The results indicated that T1,T2,T3 could damage potato seedlings.(3)Three toxins(T1,T2 and T3)that could cause disease were analyzed by UV,FT-IR and GC-MS.The results showed that the maximum absorption wavelengths of T1,T2 and T3 in methanol were 198.5 nm,199.5 nm and 199 nm,respectively,and the maximum absorption wavelengths in water all were 198 nm.The FT-IR spectrum showed characteristic bands of C=O(1735.62 cm-1)、C=C(1635.34 cm-1)and-C-O(1263.1 cm-1、1128.2 cm-1)groups in T1.T2 contained groups such as C=O(1729.8 cm-1),-C-O(286.3 cm-1)and O-H(1124.3 cm-1).T3 contained functional groups such as-CH2-(2927.4 cm-1),C=C(1591.0 cm-1)and O-H(1124.3 cm-1).The main substances in toxin T1 analyzed by GC-MS were tributyl phosphate,diisobutyl phthalate,dibutyl phthalate and(methoxymethyl)triphenylphosphonium chloride.(4)GDP technology is an effective way to degrade R.solani toxins.After degradation with GDP for 10 min,the degradation rates of T1,T2 and T3 in aqueous solution were 79.8%,87.7% and 86.8%,respectively,which indicated that the R.solani isolates in aqueous solutioncould be degraded by GDP.In addition,with the increase of GDP degradation time,the pH value of toxin degradation solution showed a tendency to decrease first and then increase.When GDP discharge 5 min with adding Fe2+,T1,T2 and T3 degradation rates increased by 30.8%,46.9% and 29.1%,respectively,which indicated that Fe2+ has a catalytic effect,the addition of ferrous salt in the GDP system can effectively accelerate the degradation process of toxins in aqueous solution.