This text deals with both host-specific and non-host specific toxins in order to describe host-pathogen interactions leading to disease development and their biotechnological exploitation using genetic engineering tools for disease and weed management.

Plant pathogens and their phytotoxins as herbicides; phytotoxins produced by alternaria brassicae and bioassay of destruxin B; the photoactivated toxin cercosporin - toxicity, resistance, regulations and role in disease; tabotoxin - structure, biosynthesis, mechanism of action and its role in disease development; the genetic engineering approach for the control of plant diseases; naphthazarins toxins of fusarium solani; cytochalasins from phytopathogenic ascochyta and phoma species; susceptibility inducing toxin(s), produced by pyricularia oryzae; phytotoxins associated with ascochyta species; culture filtrate as selective agent of resistance to phytopathogenci fungi; host specific toxins - status and perspectives.