Rapid Diagnosis Of Typical Diseases Of Navel Oranges By LIBS Scanning Analysis

The navel orange is a citrus fruit.Over the years,the navel orange industry has played an important role in poverty alleviation for farmers in southern China.However,navel orange is vulnerable to many diseases such as anthrax,decaying disease,HLB disease,yellowing disease,canker disease and so on during the growth process,which causes huge economic losses.Based on the green development view of modern agriculture in China,it is urgent to develop a rapid,in-situ,green and on-site diagnosis method for typical navel orange diseases.Laser induced breakdown spectroscopy(LIBS)has many advantages,such as eliminating the need for chemical pretreatment of the sample,simultaneous detection of multiple elements,green,fast,in situ and micro-region.It can realize qualitative or quantitative analysis of material composition,and is known as "the most dazzling new star in the field of elemental analysis".In this paper,Gannan navel orange,a characteristic fruit in Jiangxi Province,is taken as the research object to explore the feasibility of rapid diagnosis of typical navel orange diseases based on LIBS scan analysis.The main research contents are as follows:(1)The content of sugar content and major mineral elements Ca,K and Zn in the juice of healthy navel orange and HLB disease navel orange were measured respectively,and the differences in the content of sugar content and mineral elements between the two were contrasted and analyzed,and the effects of HLB disease on the internal quality of navel orange,the growth and fruit ripening of navel orange were explored.The results showed that:(1)The mean sugar content of normal navel orange was 12.8 Brix,while that of HLB disease navel orange decreased to 9.3 Brix,and there was a significant difference between the two.The sugar content of navel oranges infected with HLB disease will decrease significantly,which has a significant adverse effect on taste and edible value.(2)The content of mineral elements in pulp of navel orange with HLB disease changes to some extent.The mean contents of Ca,K and Zn in HLB disease navel orange were 612.7 mg/kg,688.9 mg/kg and39.2 mg/kg,respectively.The average contents of Ca,K and Zn in healthy navel orange were422.6 mg/kg,596.2 mg/kg and 34.5 mg/kg,respectively.The results showed that the contents of Ca,K and Zn in navel orange with HLB disease were higher than those in healthy navel orange.The content of mineral elements in pulp of normal navel orange and yellow-dragon disease were analyzed by paired sample T test.The results showed that there was a significant difference in Ca content between normal navel orange juice and HLB disease navel orange juice.There is no significant difference for K element.For Zn,there were significant differences between the two navel orange species.The t-test results of paired samples showed that the infection of HLB disease had a significant effect on the sugar content of navel orange,and the Ca and Zn elements in the pulp had a significant difference.(2)Rapid green identification of Gannan navel orange juice by using laser-induced breakdown spectrum total optical diagnosis technology.Navel orange orange juice as the research object,navel orange juice LIBS spectrum data,using smooth at nine-point(9Smoothing,9SM)combined with multiple scattering Correction(Multiplicative Scatter Correction,MSC)data preprocessing method,using principal components analysis(PCA)to carry on the simple classification,classification result is not ideal,coupled with multilayer Perceptron neural network(Multi-Layer Perceptron.MLP and Radial Basis Function Neural Network(RBF)models were used for the rapid identification of healthy navel orange and HLB disease.The results showed that the PCA-MLP model was better than the PCA-RBF model in discriminating healthy and HLB disease navel oranges.The discriminating accuracy of the training set for healthy navel oranges and HLB disease navel oranges was93.8% and 93.4%,respectively,and the discriminating accuracy of the prediction set for healthy and HLB disease navel oranges was 93.9% and 94.8%,respectively.The results of LIBS test proved that the HLB disease can cause the change of the internal quality of navel orange pulp.Further use of spectral pretreatment and classification model can distinguish HLB disease from healthy orange juice in quality,and improve the qualified rate of orange juice products.(3)Taking the early navel orange leaves of normal,HLB disease,deficiency disease,decay disease and suspected HLB disease as the research objects,the contents of total nitrogen,total phosphorus,chlorophyll and elements in the leaves were determined,and the effects of early disease on these indexes were analyzed.The results showed that:(1)The mean total nitrogen content of normal navel orange leaves was 0.969g/100 g,that of HLB disease navel orange leaves was 0.836 g/100 g,that of deficiency disease navel orange leaves was 0.777 g/100 g,and that of decline disease navel orange leaves was 0.842 g/100 g.The total nitrogen content of navel orange leaves was the highest in normal navel orange leaves and the lowest in navel orange leaves with deficiency disease.There were no significant differences in total phosphorus,chlorophyll b and c contents.The mean content of chlorophyll a in normal navel orange leaves was 6.869 mg/L,that in HLB disease leaves was8.009 mg/L,that in deficiency disease leaves was 1.330 mg/L,and that in recessive disease leaves was 2.125 mg/L.The content of chlorophyll a in navel orange leaves with deficiency disease and decay disease was significantly lower than that of normal navel orange leaves with HLB disease.(2)The mean content of Ca in the leaves of normal navel orange was16264.5 mg/kg,that of HLB disease navel orange was 19511.7 mg/kg,that of deficiency disease navel orange was 16417 mg/kg,that of decay disease navel orange was 3418.7 mg/kg,and that of suspected HLB disease navel orange was 3445.3 mg/kg.The results showed that there was no significant effect on the content of Ca in navel orange leaves at the early stage of HLB disease,but there was a significant effect on the leaves of HLB disease and suspected HLB disease.The concentrations of Cd,Cr,Cu,K and Zn in the leaves of the five kinds of navel orange were all low and the differences were not significant,while the concentrations of Mg and Na were high but the differences were not obvious.(4)Taking early navel orange leaves as the research object,collecting navel orange leaves with HLB disease,healthy,canker disease,deficiency and suspected HLB disease in southern Jiangxi,and using the method of laser induced breakdown spectrum total optical diagnosis,exploring the feasibility of early nondestructive identification of typical navel orange diseases in southern Jiangxi.LIBS spectral data were collected,nine-point smoothing(SM)and Standard Normal Variate(SNV)were used for data preprocessing,principal component analysis(PCA)was used to extract the first seven principal components,and multilayer perceptron neural network(MLP)model was used to quickly identify the five navel orange leaves.The results showed that the accuracy of PCA-MLP model for navel orange leaves training set was 93.52%,and the accuracy of prediction set was 90.4%.It can be seen that LIBS spectrum combined with appropriate pretreatment methods and classification model can be used to realize rapid diagnosis of typical lesions under LIBS scanning analysis of navel orange leaves in southern Jiangxi.The results showed that the PCA-MLP model had a high recognition rate for the typical disease types of navel orange leaves in southern Jiangxi,and could accurately identify the navel orange leaves in the early growth stage.