Open AccessDigital Image Analysis of Internal Light Spots of Appressoria ofColletotrichum acutatum
Author(s) -
Javier Diéguez-Uribeondo,
H. Förster,
J. E. Adaskaveg
Publication year - 2003
Publication title -
phytopathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.264
H-Index - 131
eISSN - 1943-7684
pISSN - 0031-949X
DOI - 10.1094/phyto.2003.93.8.923
Subject(s) - appressorium , penetration (warfare) , electron micrographs , micrograph , colletotrichum acutatum , biology , colletotrichum , scanning electron microscope , digital image analysis , inoculation , materials science , electron microscope , botany , optics , horticulture , composite material , physics , mathematics , operations research , computer science , computer vision
The initial penetration process of appressoria of Colletotrichum acutatum on almond leaves was studied using digital image analysis of light micrographs and scanning electron microscopy. For image analysis, a series of sequential, partially focused digital micrographs of appressoria was analyzed to generate a single, completely focused montage image with a continuous in-focus depth of field. In studies on the development of the internal light spot (ILS), we observed that 50.4% of the appressoria formed an ILS after leaves were inoculated and incubated for 12 h at 20°C, and that this increased to 95.8% after 24 h. Comparative image analyses of appressoria with and without ILSs using depth relief mapping and line profile software options showed that the ILS had a depth relief that was below that of the leaf surface. Depth relief analysis in the ILS region during incubation revealed an increase in depth in this area of up to 1.8 μm in some of the appressoria. A comparative morphological study of the ILS in montage images and the penetration pore of appressoria in scanning electron micrographs showed similar shapes and dimensions of the two structures in the appressorium. Light micrographs of histological sections confirmed fungal penetration and internal vesicle formation in almond leaves within 36 h after inoculation and incubation at 20°C. This study represents the first direct evidence that the ILS in appressoria corresponds to the penetration pore and the developing penetration peg using a rapid, digital image analysis technique.