PREPARATION PROCEDURES OF FUNGAL PHYTO-PATHOGENS SAMPLES FOR ANALYSIS BY MALDI-TOF AND FTIR MICROSCOPY

Reliable and rapid identification of phyto-pathogens causing plant diseases is playing an important role in their control strategies. The available methods for identification of fungi are time consuming and not always very specific. MALDI-TOF and Fourier-transform infrared (FTIR) microscopy are proved to be comprehensive and sensitive analytical methods for detection of molecular changes in cells. Due to the similarity between the obtained spectra of different species of fungal pathogens, it is important to choose the most appropriate procedure for the preparation of the examined samples. Such procedure might improve the discrimination between these species. In the present study, we compared between three possible procedures of pathogen sample preparation for their examination by MALDI-TOF and FTIR microscopy. Our results showed that preparation of the fungal sample directly from liquid growth media is considered as the best way of fungal sample preparation for both MALDI-TOF and FTIR microscopy examination

Direct Estimation of Local pH Change at Infection Sites of Fungi in Potato Tubers

Fungi can modify the pH in or around the infected site via alkalization or acidification, and pH monitoring may provide valuable information on host–fungus interactions. The objective of the present study was to examine the ability of two fungi, Colletotrichum coccodes and Helminthosporium solani, to modify the pH of potato tubers during artificial inoculation in situ. Both fungi cause blemishes on potato tubers, which downgrades tuber quality and yield. Direct visualization and estimation of pH changes near the inoculation area were achieved using pH indicators and image analysis. The results showed that the pH of the area infected by either fungus increased from potato native pH of approximately 6.0 to 7.4 to 8.0. By performing simple analysis of the images, it was also possible to derive the growth curve of each fungus and estimate the lag phase of the radial growth: 10 days for C. coccodes and 17 days H. solani. In addition, a distinctive halo (an edge area with increased pH) was observed only during the lag phase of H. solani infection. pH modulation is a major factor in pathogen–host interaction and the proposed method offers a simple and rapid way to monitor these changes. </jats:p

Direct identification of potato's fungal phyto-pathogens by Fourier-transform infrared (FTIR) microscopy

Fungi are considered as serious pathogens to many plants and can cause a severe economic damage. The available methods for identification of fungi are time consuming and not always very specific. In the present study we examined the potential of FTIR microscopy for direct detection and identification of different fungal potato pathogens on the surface of potato tubers. Unique spectral bands for each of the examined fungal pathogens appeared in the spectra of naturally infected potatoes. These results strongly support the potential of FTIR microscopy for successful detection and probably discrimination between different fungal pathogens directly from the infected tissue.</jats:p