Plant Pathogens
Although not explored extensively, FCM can be used as a convenient and rapid tool to detect plant pathogens (e.g. viruses, bacteria, and fungi), and to assess their viability (see Chapter 9). As in other applications, FCM excels in its ability to analyze large population samples in a short time and to discriminate subpopulations.
Identification of specific viruses, bacteria and fungal spores can be achieved after immunofluorescent staining of a pathogen in a crude plant extract (Chitarra and van den Bulk 2003). The number of pathogens that can be detected is, however, limited by the number of suitable antibody-fluorochrome conjugates. This problem has been solved by developing multiplex assays that involve micro-spheres conjugated to antibodies. Originally, the microspheres conjugated to different antibodies were discriminated based on their size (Iannelli et al. 1997). A recent approach used beads that are stained with two fluorochromes at different ratios. Up to 100 different bead types are now available, theoretically allowing the detection of the same number of different pathogens (Joos et al. 2000; Vignali 2000). In fact, the limiting factor for simultaneous detection of a large number of pathogens is the lack of suitable antibodies and not the number of different beads. A possible solution involves DNA-based microsphere assays (see Chapter 9).
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