Plant pathogens, discussion

Two examples have been chosen for discussion, i.e. the interactions of tomato with Pseudomonas syringae pv. tomato and with Cladosporium fulvum, a bacterial and a fungal pathogen, respectively. These two plant pathogen interactions are among the few that have been characterized not only in genetic terms but also at the molecular and biochemical levels and they are thus well suited for a discussion of the fundamental principles. 

The cell walls of many fungi contain chitin and there is evidence that the growth of hyphal tips depends on a delicate balance between cell wall synthesis and wall lysis. Chitinase can alter the balance. Later on, I will discuss this important role of chitinase for controlling soil-borne plant pathogenic pests. 

In principle, one of the most effective means to cope with resistance of plant pathogens is the use of fungicides to which resistant strains show negatively correlated cross resistance. However, until now this strategy has seen limited use in practice, principally for lack of suitably effective compounds. Herein we discuss one of the first practically useful examples of negatively correlated cross resistance, and report on its genetic and molecular basis. 

Conjugates of indole-3-acetic acid. Listed are the naturally occurring conjugates of lAA and 4-Cl-IAA from plants and plant pathogenic bacteria described to date. With the exception of the Parthenocissus spp. callus tissue, these compounds have been isolated from tissues not exposed to exogenous sources of lAA. Compounds reported prior to 1982 are discussed in a comprehensive review of lAA conjugates (ref. 2 [83]). 

Foliar Uptake Adsorption and Absorption The leaf surface provides an extensive surface area that can interact with chemicals either in the vapor phase or through wet or dry deposition. The cuticle limits water loss and protects against infection by plant pathogens. Detailed descriptions of the plant cuticle are available " and a brief synopsis has been provided in the discussion of the sorption of chemicals by foliage (see Sorption, Chapter 3). While the hydrophobic cuticle... 

In this chapter, the role of the shikimic acid pathway in virulence of a plant pathogen is discussed using indole-acetic acid (IAA) production by savastanoi as a model. 

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