Fourier transform infrared spectroscopic characterization of powdery mildew infection in mulberry leaves
Mulberry leaves are affected by a variety of fungal diseases, which alter the biochemical constituents and make the leaves for silkworm feeding. Powdery mildew (PM) infection is one of the most important fungal diseases in the sericulture industry. FTIR spectra of healthy and powdery mildew infected leaves of different mulberry varieties (AR12, AR14, BR2, S1, S13, S146, S1635, TR10 and V1) were recorded in this study to obtain possible spectral traits in PM infection detection and characterization. FTIR spectra were used to determine the types of vibrations (stretching and bending), visible intensities (v, sh, m, w) and infra red (IR) wave numbers (4000 cm-1 – 400 cm-1) of prominent peaks. The effect of powdery mildew infection was attributed to the probable differences in the spectra of healthy and infected leaves. In different varieties of mulberry leaves FTIR data reveal the presence of bonded O–H, N–H, C–H, C–C, C–O, C=O, C–O–C, SO3, and O–N=O functional groups and biochemical constituents such as phenol, amine, alkene, alkane, alkyne, carboxyl, ester, ether, polysaccharide, nitrite and sulfur compounds. The bonded O–H stretch observed in AR12 and V1 infected mulberry leaves at 3734 cm-1 and 3600.5 cm-1, respectively attributes the production of phenol due to powdery mildew infection. Similarly, the bands observed at 2967.8 cm-1 – 2958.3 cm-1 due to C–H asymmetric stretching only in S146, S1635, AR12 and V1 corresponds to the powdery mildew infection. Also, the weak absorption at 2378.9 cm-1 to 2325.1 cm-1 observed in AR12, AR14, V1, S1, S13, S146 and S1635 varieties represents the effect of powdery mildew infection and production of carboxyl group (C-O) in different varieties of mulberry leaves. The wave number of the prominent peaks of powdery mildew infected and healthy leaves differed significantly (t = 9.63, df = 80, p 0.001).
FTIR spectroscopy, Functional groups, Fungal infection, Mulberry leaves, Powdery mildew.