Research on Grape Brown Spot by FTIR

Fourier transform infrared( FTIR) spectroscopy was used to study healthy and diseased leaves of grape. The infrared spectra of non-lesion site and lesion site of grape large brown spot leaves,non-lesion site and lesion site of grape small brown spot leaves were tested and analyzed,and so did healthy grape leaves. The results show that the infrared spectra of grape leaves are mainly composed of the absorption bands of carbohydrates,proteins and lipids. The infrared spectra of healthy and diseased leaves of grape exhibit differences in the region of 1 800-1 500 cm-1for lipid and protein amide absorption,and in the range from 1 200 to 900 cm-1for polysaccharide absorption. Decomposition and curve-fitting analysis was performed on the infrared spectra of healthy and diseased leaves in the region of 1 800-1 500 cm-1. The sub-band area ratio A1657/ A1517 was used to evaluate the relative changes of proteins in the leaves,and A1738/ A1517 was used to evaluate the relative changes of lipids in the leaves. The absorption ratio I1066/ I1441 was used to evaluate the relative changes of polysaccharides in the leaves. The results indicated that the content of polysaccharides,proteins and lipids in grape brown spot leaves had decreased. Hierarchical cluster analysis( HCA) was performed on the second derivative infrared spectra of healthy and diseased leaves of grape in the range from 1 800 to 1 500 cm-1and 1 200 to 900cm-1; and can correctly cluster the grape leaf samples for healthy or diseased. All above have revealed that infrared spectra of grape brown spot leaves in the regions of 1 800-1 500 cm-1and 1 200-900 cm-1are sensitive bands.