Study On Detection Method Of Volatiles From Diseased Tomato Plants Based On Infrared Spectroscopy

Tomato as one of the most consumed vegetables in the world,will directly affect the peoples living health level.However,tomato plant diseases（such as early blight,gray mildew,etc.）cause a large number of losses of tomato fruit every year,which is of great significance to the disease and prevention of tomato plant.The qualitative and quantitative detection of VOCs related to disease will be released by tomato plants under disease stress.Most VOCs have obvious spectral absorption characteristics in the infrared band.The extraction Fourier transform infrared technology is used the results show that the combination of spectrometer（FTIR）and long-term gas absorption tank can improve the detection sensitivity and better analyze and study the trace VOCs released after the disease.The open optical path laser spectroscopy can measure the gas in a few meters or even hundreds of meters,which is suitable for the wide range measurement of plant volatiles.In view of the above two conditions,the VOCs released from tomato plants were qualitatively studied by infrared and laser spectroscopy.The main research contents and conclusions are as follows.1.The volatiles of tomato were measured by extractive FTIR combined with 20 m long optical path gas pool.Three experimental groups（early blight group,gray mold group,mechanical injury group）and one control group（healthy group）were set up the results showed that the specific absorption peaks of the volatiles from Botrytis cinerea tomato plants appeared at the wave numbers of 1027 cm^-1,1015-1013 cm^-1,1055-1053 cm^-1,1047 cm^-1and 1046 cm^-1,and the peak intensity increased significantly with the increase of infection time.The specific absorption peaks of volatiles from tomato plants infected with early blight appeared at 847 cm^-1,918 cm^-1,932 cm^-1,949 cm^-1,967-965 cm^-1,1043 cm^-1 and 1053 cm^-1,and the peak intensity increased with the extension of infected days.By comparing the infrared spectra of the standard compounds in NIST library,it was found that ethylene,terpinene-4-ol andβ-caryophyllene had obvious infrared absorption peaks at the wavenumbers of 949 cm^-1,967 cm^-1,1043 cm^-1,1027 cm^-1,1056 cm^-1 and 1015-1013 cm^-1,which could be used to determine the existence of these substances in the volatiles of infected tomato plants.2.The volatiles of tomato plants were detected by open path laser spectroscopy.The quantum cascade laser（QCL）was selected as the light source,and the tunable diode laser absorption spectroscopy（TDLAS）was established according to the selected spectral range and the characteristics of the laser(normal operation in the wave number range of 958 cm^-1-1158 cm^-1),the overall structure of the system is designed.According to the experimental requirements,a set of software was developed to process the original data.The final experimental results show that the open path laser spectrum can detect the volatile compounds of diseased plants.In summary,extractive fourier transform infrared spectroscopy can be used to identify ethylene in the volatiles of tomato plants infected with early blight andβ-caryophyllene and terpinene-4-ol in the volatiles of tomato plants infected with gray mold.The results of FTIR are consistent with the experimental results.This study shows that infrared and laser spectroscopy technology can be applied to the rapid and online measurement of plant volatiles,and it is expected to realize the early warning of plant diseases through the measurement of volatiles.